Part III. Experience in the Caribbean Defense Command

ORGANIZATION

General

    The Caribbean Defense Command was activated 8 May 1941, with headquarters at Quarry Heights, C.Z. ³⁷ General Orders No. 8, issued 29 May 1941, defined the Command as consisting of the "islands in or bordering the Caribbean Sea, the Guianas, Venezuela, Colombia, Ecuador and the countries of Central America (except Mexico)."  The same announcement created three sectors to be known as the Trinidad Sector, the Puerto Rican Sector, and the Panama Sector.

³⁵ (1) Harris, R.R.: Malaria Control in Central America. Proc N. J. Mosq. Extermin. Ass, 38: 154-158, 1946. (2) Bishopp, F. C., and Stage, H. H.: A Review of Contributions to the Knowledge of Mosquitoes around the World during 1945. Proc. N. J. Mosq. Extermin. Ass. 33:123-147, 1946.
³⁶ Gabaldon, Arnoldo: Malaria Control in the Neotropic Region. In Malariology, edited by Mark F. Boyd. Philadelphia: W. B. Saunders Co., 1949, vol. II, pp. 1400-1415.
³⁷ A History of Medical Department Activities in the Caribbean Defense Command in World War II, Vol. I, pp. 131-132, May 1946. [Official record.]

    The Caribbean Defense Command was thus formed of the long-established, but recently expanded, PCD (Panama Canal Department), ³⁸ together with the Puerto Rican Department, which had come into existence in May l939,³⁹ and whose headquarters were located at San Juan, P.R., and which included the Virgin Islands. To this combination was added the Trinidad Base Command, and all the posts and installations, insular or continental, geographically associated. These included the various new bases to the southward, which had been established as a result of negotiations with the Netherlands and with Great Britain.

    The practice of referring to "Atlantic" and "Pacific" Sectors within the PCD appears not to have been continued into the war years. The entire PCD thus became a single sector, of the same name.

    This arrangement, however, was not permanent. The Caribbean Defense Command underwent a number of internal administrative changes before the end of the war, the essential features of which may be summarized, as follows:

    Confusion arose almost at once as to the relation of the Trinidad Sector (and Trinidad Base Command) to the former Puerto Rican Department. This was clarified in June 1943, by the establishment of the Antilles Department, with Headquarters at San Juan, which eliminated the Puerto Rican Department, as such, and placed the Puerto Rican and Trinidad Sectors on an equal footing within the new administrative unit. This continued into 1944, when the two subordinate sectors were in turn eliminated and all posts in the Antilles came under the direct control of Antilles Department Headquarters.

    The Sixth Air Force was a part of the Caribbean Defense Command but had the same area of control as the Command itself. It was administered by the Sixth Air Base Command.

Medical

    For some time after the establishment of the Caribbean Defense Command, no centralized direction of medical affairs was authorized.⁴⁰ Each major subdivision of the Command continued to handle its own medical problems and to send reports directly to Washington, D.C.  The surgeon of the PCD or the chief health officer of the Panama Canal were available for consultation in special cases.

    The Corps of Engineers maintained a medical service for its civilian employees, which functioned side by side with the Army Medical Services.

    The first step toward the establishment of an office of the surgeon for the entire Command came about on 14 June 1943, when Maj. (later Col.) Daniel Bergsrna, MC, arrived from the United States to serve the headquarters staff, with special responsibility for venereal disease.

³⁸ Before 1940, the Panama Canal Department was restricted to the Canal Zone.
³⁹ War Department Pamphlet 8-2, 2 Apr. 1943.
⁴⁰ Annual Report, Office of the Surgeon, Caribbean Defense Command, 1943.

    On 13 October 1943, Brig. Gen. (later Maj. Gen.) Morrison C. Stayer, incumbent chief health officer for the Panama Canal, was designated as surgeon of the Caribbean Defense Command, and an "Office of The Surgeon" thus became established. After this date, most of the medical reports from both the Panama Canal and Antilles Departments passed through this headquarters for review and consolidation before being sent to Washington. This was a great advantage to the Caribbean Defense Command, as many decisions involving change of policy could be rendered by the Command surgeon, and the necessary procedures could be put into effect without waiting for directives from Washington, where there was not always complete understanding of practical conditions in the field.

    By the end of 1943, General Stayer and his assistant, Major Bergsma, already familiar with the malaria situation in the Panama Canal Zone and adjacent territory, had made special malaria studies in both the Puerto Rican and Trinidad Sectors of the Antilles Department.

    The Sixth Air Force served three "Areas" corresponding to the "Sectors" of the Caribbean Defense Command. Seventeen airbases were involved. In 1942, the situation for the Panama Area (seven bases) was as follows:

Name of base................................................ Medical officers
Albrook Field, C.Z.............................................6 (4 of these on duty status).
France Field, C.Z...............................................4 (2 of these on duty status).
Howard Field, C.Z.............................................2 (both on duty status). (Surgeons, 16th Air Base Group, Acting Base Surgeon.)
Rio Hato, R. de P...............................................2
Guatemala City...................................................2 (on duty status from Howard Field and France Field)
Galá pagos Islands. Ecuador...............................2 (on duty from Albrook Field)
Salinas, Ecuador.................................................3 (all on duty status; 1 each from Howard Field, Albrook Field, and France Field).

    In 1942, the situation for the Trinidad area (five bases) was as follows:

Name of base ................................................ Medical Officers
Waller Field, Trinidad, B.W.I.............................1 medical officer.
Beane Field, St. Lucia, B.W.I............................None (that is, Post Surgeon, not Air Force. Surgeon, 5th Bombardment Squadron here, however).
Hato Field, Curacao, N.W.I..............................None (Surgeon, 59th Bombardment Squadron here).
Atkinson Field, British Guiana............................(Surgeon, 44th Reconnaissance Squadron here.)
Zandery Field, Surinam......................................1.

    In 1942, the situation for the Puerto Rican Area (five bases) was as follows:

Name of base................................................ Medical officers
Borinquen Field, P.R..........................................14 medical officers (hospital facilities for 290 beds).
Losey Field, P.R.................................................9 medical officers (hospital facilities for 96 beds).
Benedict Field, St. Croix.....................................(Surgeon, not Air Force.) (Surgeon, 12^th Bombardment Squadron here.)
Coolidge Field, Antigua.......................................(Surgeon , not Air Force.) (Surgeon, 35^th Bombardment Squadron here).
Vernam Field, Jamaica........................................(Surgeon, not Air Force).

    In 1942, the personnel of the Sixth Air Force were not well provided for in the matter of medical care. This was particularly true in the field of preventive medicine, although reasonable protection was achieved through the environmental sanitation program of the Army Ground Forces. The Air Force was particularly vulnerable to malaria, because of frequent missions into and out of malaria areas. Infected Air Force personnel could also serve as new reservoirs, on return to base, as did troops of all organizations when evacuated from malarious territory.

PANAMA CANAL DEPARTMENT

    The malaria control activities of the Caribbean Defense Command will be treated in two units, pertaining to the two Departments as finally constituted. These will be followed by a special section dealing with the Sixth Air Force.

    As already stated, this Department represented an expansion of military activities normally limited to the Canal Zone, but which, in the interest of hemisphere defense required the establishment of numerous installations in adjacent territory. At its greatest expansion, the Department extended from about 20^º north latitude to 5º south latitude and from 77º to 89º west longitude.

    A brief statement concerning the malaria hazard, including facilities for control, will be given for each of the Republics or dependencies in which the Army operated. These statements pertain chiefly to conditions prevailing at the outbreak or during the early period of the war.

Countries and Dependencies Concerned

    Guatemala . - National public health administration is a function of the Bureau of Public Welfare, which was organized by presidential decree in August 1941. ⁴¹ Its activities include special programs for malaria control.

    In this country, the rainy season extends from December to May, while the remainder of the year is relatively dry.⁴² The greatest rainfall is on the Atlantic side. Malaria is severe and almost universal on the coasts; it is also serious in the river valleys.

    Early campaigns against mosquitoes were confined chiefly to oiling and dusting and were not especially effective. Drainage projects were few and insignificant as compared with the obvious need.

    Anopheles albimanus is the principal malaria vector, being found on both coasts as well as in the Petén district. Anopheles pseudopunctipennis, however, is prevalent in the central highlands, while A. vestitipennis proved the major vector in the camps along the Cobán-Petén highway. Anopheles darlingi is found in Petén province and around Lago de Izabal.

⁴¹ Medical and Sanitary Data on Guatemala. compiled by the Medical Intelligence Branch, Preventive Medicine Division, Office of The Surgeon General, U.S. Army, 15 June 1943.
⁴² Report, Lt. Col. V. H. Cornell, MC, U.S. Army, subject: Sanitary Survey of Guatemala, 12-20 Mar. 1941.

    By 1943, more lasting control measures had been instituted in the environs of Puerto Barrios, Guatemala City, San José, and along the route of the Pan American Highway. Topographic surveys were also underway, as a basis for long-range, permanent improvements.

    Honduras. - In 1941, the health department of Honduras was reported as rather poorly organized, with an inadequately trained staff .⁴³ From a sanitary standpoint, therefore, any military force had to be prepared to supply its own protection and facilities.

    On the north coast, there is much rain. The period from February through June is most moderate in this respect. In the south, however, conditions are quite different, with two short rainy periods which fall in May and late October or November. In the mountainous areas, on the other hand, rain prevails from April to October. Malaria is serious in the north, which is characterized by many broad swamps; also in the south, though here the disease is more seasonal. Drainage is especially poor about the Gulf of Fonesca, and there is much malaria along the winding, lower courses of streams and rivers which flow into it. In the highlands, the disease occurs chiefly in persons "from the coasts."

    In 1941, mosquito control had been practiced in "Company" areas and to a lesser extent in villages near them. Efforts at oiling and drainage were both so sporadic, however, that little good had resulted as extensive breeding areas nearby had been left quite undisturbed. By 1943, however, the Inter-American Cooperative Public Health Services had begun to function, and projects for malaria control were developed in several regions, including the ports of Amapala on the Pacific side and Puerto Castilla on the Atlantic coast. There was also provision for emergency malaria control in the camps of the workers on the Pan American Highway and on the Potrerillos-Pito Silo road.⁴⁴

    British Honduras, though within the general area of the Caribbean Defense Command, is not properly within the scope of this discussion. It is nevertheless of interest to note a British report for 1939.⁴⁵ During that year, 653 cases of malaria were admitted to public hospitals in the colony; 31 hospital deaths were ascribed to malaria, with 84 deaths in the colony as a whole. Outpatient cases treated at hospitals numbered 4,115.

    El Salvador . - Although it is the smallest of the Central American States, El Salvador has a Ministry of Agriculture and Public Health which includes a Preventable Disease Division. The latter is organized into five subdivisions, one of which is concerned wholly with malaria problems.⁴⁶

⁴³ Report, Lt. Col. V.H.  Cornell, MC, U.S. Army, subject: Sanitary Survey of Honduras, 1-7 Mar. 1941.
⁴⁴ Medical and Sanitary Data on Honduras. Prepared by the Medical Intelligence Branch, Preventive Medicine Division, Office of The Surgeon General, U.S. Army, 15 Sept. 1943.
⁴⁵ Medical and Sanitary Reports from British Colonies, Protectorates and Dependencies for the years 1939-1941. British Honduras (1939). Trop. Dis. Bull. 48 (Suppl.) : 217-219, 1946.
⁴⁶ Report, Lt. Col. V. H. Cornell, MC, U.S. Army, subject: Sanitary Survey of El Salvador, 7-12 Mar. 1941.

    It should be remembered that El Salvador has no Atlantic coastline. For various reasons, it was the southern (coastal) portion which was considered most important from a military standpoint. For example, El Salvador is the only port on the Gulf of Fonesca where the water is deep enough for fairly large ships to tie up.

    This region is tropical. The dry season extends roughly from December to April. There is a great increase in malaria in the rainy season.

    In 1941, malaria control in El Salvador was "in its infancy." Surveys by spleen palpation and blood smears had been made by Dr. Henry W. Kumm of the Rockefeller Foundation, and a drainage demonstration project had been conducted at San Miguel. Malaria was the great scourge of the country, beyond a doubt., but practical control measures had not been put into practice on an effective scale. It was necessary for military personnel to make provision for their own protection.

    It is perhaps worth mentioning that El Salvador has the densest population of any area on the mainland in the Caribbean and Gulf regions.

    Nicaragua . - The National Health Department is headed by the Secretary General who is also The Surgeon General of the Army. This Department, which replaced the Health Division of the former Ministry of Health and Welfare, has eight administrative subdivisions, including the Central Public Health Laboratory (also known as the National Institute of Health). There is a Rural Hygiene Division which attempted campaigns against malaria, before 1943, but with indifferent success. ⁴⁷

    On the Pacific side, the rainy season continues from some time in May to early December. On the Atlantic side, the dry season is much shorter, or absent. In the more thickly populated western areas, the temperature is high, with April and May most depressing, due to cessation of the trade winds. The rainfall at San Juan del Norte is especially heavy.

    A possible canal route exists up the Rio San Juan on the Atlantic side, through Lake Nicaragua and Lake Managua, and across a narrow strip of land to the Pacific.

    Malaria is prevalent, and there is a constant reservoir in the native population, which lives almost entirely in unscreened houses. It was realized by the military authorities that any operations aimed at clearing the region along the Rio San Juan would both increase population and improve breeding conditions for vector anophelines in that region. In the 1941 survey, Lt. Col. Virgil H. Cornell, MC, stated that malaria was a menace, all along the coasts, in the river basins and about the lakes.⁴⁸

    The principal vector, as in other Central American countries, is A. albimanus. Anopheles aquasalis, A. pseudopunctipennis, and A. argyritarsis

⁴⁷ Medical and Sanitary Data on Nicaragua. compiled by Medical Intelligence Branch, Preventive Medicine Division, Office of The Surgeon General, U.S. Army, 7 Nov. 1942.
⁴⁸ Report, Lt. Col. V. H. Cornell, MC, U.S. Army, subject: Sanitary Survey of Nicaragua, 23 Feb.-1 Mar. 1941.

are also present. Malaria reaches its highest incidence at the beginning of the rainy season (May and June) and again at the end (October to December) when optimum breeding conditions abound. Malignant tertian malaria predominates.

    Costa Rica, 1941. - The government has a department of public health with a number of subdivisions. At least four of these have some interest in malaria. The Rockefeller Foundation and the Pan-American Sanitary Bureau extend advisory services.⁴⁹

    The long coastal areas were of the greatest interest from a military standpoint. The dry season extends from December into April. The rain on the Atlantic coast is heavier. Malaria increases with the wet season, the peak falling about 1 month after the peak of rainfall. Sixteen kinds of Anopheles have been found in Costa Rica, but only A. albimanus is an important vector ⁵⁰ Official mortality statistics for 1940 reported 916 deaths from malaria, or 140 per 100,000 for the entire country. Since 75 percent of the people live in the relatively healthy central plateau, this means a death rate approaching 500 per 100,000 in the coastal regions. (In the same year, the highest malaria death rate in the United States was 9.1 per 100,000 reported in Arkansas.)

    With the assistance of the Rockefeller Foundation, considerable anti-malaria drainage had been carried on, particularly in the province of Guanacaste.

    Republic of Panama .- The Ministry of Public Health in 1943, through its Malaria Section, operated a Division of Malaria Studies. Its activities were directed chiefly toward antimosquito work. Eight projects, employing 366 nationals were being carried on,⁵¹ and an intensive health education program was in operation. In addition, the Division of Sanitation had two technicians for malaria studies on the staff of its chief sanitary inspector.

    The Division of Health and Sanitation of the Office of the Coordinator of Inter-American Affairs cooperated with the Republic of Panama on its malaria program, which consisted largely of drainage, entomological studies, ditch construction, larvicidal work, and ditch maintenance.

    These agencies served the urban centers well, but many parts of the interior lacked any organized public health work. The United Fruit Company, however, had a comprehensive health program which included malaria and insect control.

    The population is concentrated along the seacoasts and rivers. Certain large areas are sparsely populated. Malaria is the principal health problem, from both a civilian and a military standpoint. Anopheles albimanus is the

⁴⁹ Report, Lt. Col. V. H. Cornell, MC, U.S. Army, subject: Sanitary Survey of Costa Rica, 12-23 Feb. 1941.
⁵⁰ Medical and Sanitary Data on Costa Rica. compiled by Medical Intelligence Branch, Preventive Medicine Division, Office of The Surgeon General, U.S. Army, 7 July 1943.
⁵¹ Medical and Sanitary Data on the Republic of Panama and the Panama Canal Zone, compiled by Medical Intelligence Branch, Preventive Medicine Division, Office of The Surgeon General, U.S. Army, 26 Nov. 1943.

principal vector with A. punctimacula in second place. Six other species are perhaps involved.

    Clark and Komp ⁵² have shown that in certain villages of Panama, over a 10-year period, no seasonal variation in malaria occurred which could be correlated with seasonal rainfall.

    Panama Canal Zone . - The chief health officer, Panama Canal Zone, is selected from the Army Medical Corps and serves for a period of 1 to 5 years.⁵³ His assistant is a civilian, who has direct charge of sanitation and malaria control. Field sanitation work operates by the Northern, Pedro Miguel, Panama Suburban, and Ancon-Balboa districts. For malaria control work in the Zone, certain geographic areas are allotted to the Medical Department of the Panama Canal. This is by mutual agreement between the chief health officer of the Panama Canal and the surgeon of the Panama Canal Department of the Army.

    Antimosquito work had been diligently carried out for many years, but up to 1943 no effective method had been found to prevent anopheline breeding in Gatun Lake or outlying jungle streams, pools, or swamps. Neither could the flight of these mosquitoes into sanitated areas at certain seasons be prevented. Malaria was the chief cause of illness in the Canal Zone, though deaths were rare.

    Precipitation in the Canal Zone tends to be considerably greater on the Atlantic side than on the Pacific coast. Average temperatures and relative humidity are not significantly different. The data in table 19 are instructive.

TABLE 19.- Average temperatures, reduce humidity, and precipitation in the Canal Zone, 1943-45

    The principal dry season starts in January and ends in April. During this period, mosquito breeding reaches a low ebb. The wet season begins in May and with some fluctuations lasts until December. The greatest mosquito (and malaria) menace comes with the change of seasons. Thus, the highest malaria rates are usually recorded in June or July, and the next highest in

⁵² Clark, Herbert C., and Komp, William H. W.: A. Summary of Ten Years of Observations on Malaria in Panama with Reference to Control with Quinine, Atabrine, and Plasmochin without Anti-Mosquito Measures.  In A Symposium on Human Malaria. Edited by F. R. Moulton. Washington: Publication No. 15. American Association for the Advancement of Science, 1941, pp. 273-284.
⁵³ See footnote 51, p. 171.

December or January. In both cases, this is due to the abundance of shallow water, ideal for the rebreeding of anophelines. Anopheles albimanus has long been known as the principal vector.

    The maximum number of troops on duty in the Canal Zone at any time probably did not exceed 70,000. These became widely scattered as the program for hemisphere defense materialized. At many automatic weapons and antiaircraft stations, the chief antimalaria procedure was the administration of suppressive Atabrine therapy. Some lots of Atabrine proved inferior in solubility. Attempts were made to safeguard men on night duty by spraying their uniforms with pyrethrum extract before a 2-hour detail, with inconclusive results.

    Colombia. - Very few American troops were stationed in Colombia

    Ecuador, 1943. - The Ministry of Social Welfare, Health, and Labor included a public health system of undesirable complexity, which, for lack of centralized authority, had not functioned efficiently.⁵⁴ The average longevity in the country was only 32 years. Malaria was one of several diseases of military importance. Epidemics of plague, smallpox, and typhus occurred annually. Nevertheless, of 62,183 registered deaths in 1940, 4,847 were listed as due to malaria.

    Anopheles albimanus and A. pseudopunctipennis are the proved malaria vectors, the first on the coast, the second in the mountain valleys. Drainage, ditching, and oiling had been carried out to some extent in the valleys, but, in the coastal zone, the numerous swamps could only be drained with great difficulty and excessive cost, and no progress had been made.

    It appears certain that a large portion of the population suffers from malaria throughout the year, with inevitable loss of time and reduced capacity for work. The general backwardness of many parts of the country is due at least partly to chronic malaria. The greatest seasonal peak coincides with the termination of the rains, usually in May or June.

    Galápagos Islands. - There are no anopheline mosquitoes on any of the islands. ⁵⁵ The only culicine species recorded is Aedes taeniorhynchus, a potential vector of yellow fever and dengue. Military authorities took cognizance, however, of the possibility that both human gametocyte carriers and vector anophelines might be introduced in connection with the transport of troops and goods. This never occurred.

    Peru, 1943 . - Official public health work is controlled by the Public Health Division of the Ministry of Public Health and Social Welfare.⁵⁶ The Division has six administrative sections. Malaria control is a responsibility of the Section of "Technical Services," also of the Section of "Sanitary Campaigns."

 ⁵⁴ Medical and Sanitary Data on Ecuador. Prepared by Medical Intelligence Branch, Preventive Medicine Division, Office of The Surgeon General, U.S. Army, 1 Oct. 1943.
⁵⁵ Medical and Sanitary Data on the Galápagos Islands. Prepared by Medical Intelligence Branch, Preventive Medicine Division, Office of The Surgeon General, U.S. Army, 8 Sept. 1943.
⁵⁶ Medical and Sanitary Data on Peru. Compiled by Medical Intelligence Branch, Preventive Medicine Division, Office of The Surgeon General, U.S. Army, 1 Sept. 1943.

    The Rockefeller Foundation has collaborated for years with the Peruvian Government in the fight against malaria. Since 1942, the Institute of Inter-American Affairs has been a vital influence. Malaria surveys were carried out north of Lima, in the Chimbote area. Swamps were cleared, and technicians were trained for malaria control work.

    The incidence of malaria is high in most of the country, but particularly so in coastal areas and deep-cut valleys where the chief vector is A. pseudopunctipennis . Control measures, chiefly by spraying, have been found very successful in certain valleys.

    In jungle areas east of the Andes along the Amazon River, A. albimanus is thought to be the important vector. American military interests, however, were confined largely to the coast.

Development of Control in the Panama Canal Department, 1941-45⁵⁷

    As contrasted with Pacific and African theaters, the PCD had seen malaria control campaigns for many years, going back to the work of Col. (later Maj. Gen.) William C. Gorgas in 1904.

    When the Department was officially established, such activities came within the jurisdiction of the Department surgeon. Besides his organization, however, there continued to function the Sanitary Division of the Office of the Chief Health Officer, Panama Canal.

    Until 1944, the malaria rate per 1,000 per annum among military personnel in the PCD continued to be at least twice the rate among employees of the Panama Canal. This was undoubtedly due to the fact that the soldiers operated away from home stations at least part of every year. The native reservoir of gametocyte carriers was always great and vector anophelines abundant. The problem was much aggravated in 1940, when emergency conditions required the troops to take to the field during the rainy season. Quinine was used as a prophylactic drug but with indifferent success. Only a very poor repellent, the English Dovers cream, containing oil of citronella, oil of cedar, and hard and soft paraffin was available. Pyrethrum in kerosene, 1 to 20, was the anti-mosquito spray, which had to be applied twice daily in all buildings. Protective clothing was used, and bed nets were required outside of sanitated areas. The system of mosquito control orderlies had already been instituted in the fall of 1940.

    Construction work, which increased in 1941, often blocked ditches and otherwise created new mosquito-breeding areas. Col. Wesley C. Cox, MC, Surgeon, Panama Canal Department, stated: "The Field Sanitary Force oiled all impounded water, but areas of new danger were created almost faster than they could be oiled."

⁵⁷ Unless otherwise indicated, all data in the remaining section on the Panama canal Department are based on the Annual Reports, Department Surgeon, Panama Canal Department, 1941-45, and the Professional History of Preventive Medicine in World War II, 1 January 1940 to 1 October 1945. The Panama canal Department, vol. II. [Official record.]

    Tents had to be used, even at permanent stations, to house newly arrived troops. It was practically impossible to mosquitoproof a pyramidal tent. Even buildings were difficult to keep mosquitoproof. One regiments quarters had to be completely double floored to accomplished this.

    All newly arrived units were given antimalaria instruction, hut few took this seriously until taught by experience. For example, during combat training, the men rolled up their sleeves, opened their collars at night, and dispensed with head nets in order to see better. At antiaircraft positions, troops were observed sleeping beside their guns and other equipment, rolled up in their mosquito bars.

    On the Atlantic side, malaria incidence increased as a result of a coral sand hydraulic fill, which prevented the tide water from entering the mangrove swamps. The mangroves were killed by the heavy deposit of sand, and this removed the shade. Thus an area which had previously supported only A. aquasalis became ideal for A. albimanus, the more important vector.

    Many of these activities went on in close proximity to localities where the native population was 100 percent infected. Much malaria was also brought in by the thousands of civilian laborers, imported from the West Indies and from other Central and South American Republics.

    The tide was turned in 1943 by the advent of the new repellents, the Freon-Aerosol bomb, and by Atabrine in sufficient quantities for issue to troops. Most important, of course, was an intensified educational campaign, including the use of posters and projection slides to acquaint every soldier and civilian with the seriousness of the fight against "Ann" or "Miss Anopheles."

    It is of interest to note that the term "malaria discipline" was devised and first used in the PCD in 1941. The term caught on and was adopted by unit commanders everywhere.

Problems of 1941. - Since the inception of the defense period in 1939, ever-increasing number of troops belonging to the Panama Coast Artillery Command, the Panama Mobile Force, and the Air Corps were so stationed as to be living under field conditions, away from established posts or sanitated areas. The rates for malaria in 1940 and 1941 reflect this added risk as shown in table 20.

TABLE 20. - Malaria rates for primary and recurrent cases among U.S. Army personnel, Panama Canal Department, 1939-41.

    Rates by year, however, give but a poor understanding of the seasonal problems involved. Thus, for 1941, rains in May resulted in a considerable

TABLE 21.- Malaria rates for primary and recurrent cases among U.S. Army personnel, Panama Canal Department, by month, 1941

increase in the primary malaria rate for June, while similar precipitation in August caused a high peak in September (table 21).

    It is of interest to note that it is the primary rate which fluctuates significantly in response to vector activity. The recurrent rate, as is clearly seen, shows no consistent seasonal fluctuation.

    The great height of the peak that occurred in September 1941 was due to a lapse of malaria discipline among units more or less new to the Department. In units where antimosquito and antimalaria discipline were kept up, no such rise occurred. All troops not living in barracks received quinine prophylaxis. A total of five deaths from malaria are recorded for 1941.

    The following preventive measures involved all available procedures but were incomplete in some respects: Housing in screened barracks, wherever possible; use of mosquito nets or bars by all personnel not housed in screened barracks; use of head nets, gloves, and leggings whenever use of same would not interfere with the military duties to be performed; use of prophylactic quinine; antimosquito measures at all military installations and in an ever-widening circle around these installations (not planned in relation to flight range of vector); use of mosquito repellents, antimosquito sprays, oiling of standing water, and use of other larvicides.

    Military personnel continued to be exposed to new infection in at least three ways: (1) Through duty at field positions, emergency airfields, and temporary camps; (2) through association with many chronic malaria carriers among the civilian population, and in the presence of anopheline vectors; and (3) through visits to native villages and establishment of temporary or common law relations with native women.

    Problems of 1942 . - In January, a number of military units arrived in

the PCD and were assigned to combat positions in the interior of Panama. These were indoctrinated in malaria control, but the low malaria rates of the first 3 months were due more to the dry season than to malaria discipline. The rate for primary malaria dropped from 50.3 per 1,000 per annum to 28.1 between January and April, which doubtless contributed to a false sense of security. The real situation was demonstrated by maneuvers held during the first 2 weeks of April. Rains, which had begun in March, continued during the maneuver period. Many men contracted infection during these activities and during the weeks which followed. All troops were living under actual combat conditions during May and June; as a result, the primary malaria rate for the Department rose to 233 per 1,000 per annum and the recurrent rate to 25, giving a combined rate of 258. This declined gradually during the next several months reaching 90.4 by November.

    Use of antimosquito cream, spraying of barracks with Pyrocide-20, and quinine prophylaxis for all men not quartered in mosquitoproof barracks constituted the control program for the period cited. This was manifestly insufficient.

    An even more striking demonstration was furnished by the experience of a combat team of 4,000 which trained night and day under field conditions for almost the entire month of December. The primary malaria rate in this organization rose to 274.9. Even the Panama Mobile Force (of which the Combat Team was a part) had a rate of only 126.5 for the same period, while for the remainder of the Department the primary rate was only 32.1.

    For the PCD as a whole, the rates for the year 1942 were: Primary malaria, 87.1; recurrent malaria, 24.6; total, 111.7.

    During the first part of 1942, the majority of the troops in the field were under tentage. While barracks, hutments, messhalls, kitchens, and recreation halls were being constructed, tents were screened whenever possible. Galvanized screening rusted out very rapidly here, as in all humid tropical situations.

    At several coast artillery positions, both barracks and hutments were provided. There was regular inspection, not only of the screening but also of the eaves, doors, roofs, and walls. Minor repairs, to stop all holes where mosquitoes might gain ingress, were carried out at once. A caulking compound, made of shredded paper, flour paste, sand, and cement, was found quite satisfactory for closing openings in eaves and cracks in sidewalls and proved very durable. Salvage screening was used for larger apertures.

    The provision of screened recreation rooms proved of great importance, especially in field positions. The men could thus be protected during the evening hours, when the anopheline mosquitoes were most likely to feed. The same rooms served for instruction and study. All kitchens and messhalls in field positions were also mosquitoproof. During this particular period, the newer mosquito repellents were not yet available to the Department. "Stayaway" had been found effective but had been discontinued because of its toxicity to man.

    For most of 1942, the contrast between permanent posts (sanitated areas) and outposts (unsanitated areas) was very great. The following rates (table 22) per 1,000 per annum are for primary malaria only.

TABLE 22.- Malaria rates for primary cases only, in U.S. Army personnel, in permanent (sanitated) posts and outposts (unsanitated) areas, Panama Canal Department, January-November 1942

    Again, if the rates are analyzed according to organizations with contrasting types of duty, the same facts are brought out. For example, the month of November showed a primary malaria rate of 53.9 per 1,000 per annum for the entire Panama Canal Department. However, the Panama Mobile Force, which carried out such duties as road and beach patrol and engaged in intensive unit training, had a rate of 116.5, while all other units enjoyed the relatively low rate of 34.2.

    Several additional factors also contributed to the high malaria rate in 1942, which by June had reached 258 (primary and recurrent) per 1,000 strength per annum.

    It was sometimes difficult or impossible to carry out effective mosquito control procedures during the course of construction, which, in itself frequently created new mosquito breeding areas, or, new construction work might actually block existing antimosquito drainage, which happened, for example, at the Majawar River and the Río Chilibrillo.

    Again, whereas the Army was successful in sanitating an ever-widening circle around each military post, camp, or station in the Canal Zone, existing treaty arrangements with the Republic of Panama did not make it feasible for the Army to carry out antilarval measures in unleased extracantonment areas in the Republic.

For these and other reasons, more than usual reliance had to be placed on drug prophylaxis, bed nets, repellents, protective clothing, and avoidance of civil communities at night. Enforcement was hardly adequate.

    The following recommendations were suggested in the Russell-Boyd report:⁵⁸

    1. That a medical officer, experienced and suitably trained in military malaria control methods, be made malariologist to the PCD, to organize, coordinate, and supervise military malaria survey and control work in the Department. (Possibly this officer could serve concurrently as malariologist to the Caribbean Defense Command. Such an organization had been suggested on 24 October 1942, in a letter from The Surgeon General to the Commanding General, Caribbean Defense Command.)

    2. That an entomologist and a sanitary engineer trained in malariology be assigned to this antimalaria organization. These might be suitable officers already serving in the PCD, or, if requested, specially trained men available through the Office of The Surgeon General.

    3. That, where not now in use, specific and detailed plans and spot maps for malaria control in each station in the PCD be prepared, with responsibilities and routine procedures clearly defined.

    4. That the question be studied as to how to obtain active help from the Republic of Panama Health Department in dealing with extracantonment malaria, analogous to that already being given by the Canal Zone Health Department in extracantonment areas.

    5. That every effort be made to maintain the current high efficiency of mosquitoproofing in all military stations of the PCD, that steps be taken to provide a more adequate supply of noncorrosive wire screen cloth of not less than 16 mesh, and that all construction be in accord with the principles of modern mosquitoproofing.

    6. That, if possible, no more mosquito bars or bed nets, made of "buttercloth," "tobacco cloth," "cheesecloth," or other material impermeable to air circulation, be issued for use in such tropical areas as the PCD.

    7. That ample quantities of Quartermaster issue mosquito repellent lotions (Indalone, replaced by Rutgers 612 as soon as available) be requisitioned for liberal use by troops in the PCD.

    8. That much greater use be made of pyrethrum sprays to kill adult mosquitoes, especially in the early morning and evening hours, that ample supplies of the new Freon-pyrethrum insecticide dispenser be obtained, that the practice of issuing insecticide sprays only "'within limit of funds available" be discontinued, that antimalaria supplies of all kinds, including paris green, oil, pyrethrum insecticides and repellents, be issued on an "as required" basis in such a malarious area as the PCD.

    9. That measures for anopheline mosquito control on all new projects be carried forward concurrently with construction and with the same priority, and that care be taken in new construction not to increase the malaria problem by blocking drainage or by creating new breeding places.

⁵⁸ Report, Dr. Mark F. Boyd and Lt. Col. Paul F. Russell, MC, to The Surgeon General, 5 Nov. 1942, subject: Malaria Tour in the Panama Canal Department.

    10. That in order to reduce the large numbers of malarial infections now being acquired in towns and villages where the disease is prevalent by soldiers on pass during the usual leave hours from 1300 to 2300, the possibility be considered of changing leave hours in some stations so that they would come between 0800 and 1800.

    11. That prophylactic, or in other words, suppressive treatment of malaria be reduced within the PCD to the greatest extent compatible with local conditions, and that it be administered on a specific rather than general basis, that is to say, applied only to those positions where the need for this emergency treatment can be demonstrated.

    12. That the possibility be considered of treatment with Atabrine, by Army medical officers, of all laborers on Army projects who are quartered at night within close proximity to Army positions in the PCD.

    In regard to No. 4 above, a plan was ultimately evolved by which the Coordinator of Inter-American Affairs would appropriate a sum of money, to be matched in part by funds appropriated by the government of Panama, for the purpose of carrying out a malaria control program in the Republic.

    Successful conquest of malaria, 1943-45. - During 1943, an excellent standard for malaria discipline was maintained in the Panama Canal Department. Each barracks or hutment was served by a malaria control orderly whose duty it was to spray the building twice daily, between 0500 and 0530 and between 1800 and 1900, using a Freon-Aerosol dispenser. These orderlies also eliminated casual water in ruts, tire tracks or depressions, cleaned and maintained eaves drains and other drains or ditches near the barracks, and every 7 days oiled all casual water near the barracks that could not otherwise be eliminated. They performed inspections of doors, screens, and walls of barracks, making minor repairs on the spot, and reported major defects for action on the part of the unit commander.

    Garnishing of salvaged canvas was used on inner surfaces of doors and along door jambs at field positions. Improvised caulking material composed of shredded paper, flour paste, sand, and cement continued to be useful, especially in sealing cracks at the eaves where corrugated roofing was used.

    The general success of these efforts is registered in the malaria rate (table 23).

    The peak figure for primary malaria, reached in June 1943, is trivial as compared with the previous year, and the small seasonal peak indicated for October is inconsequential. In general, it may be said that there was a steady decline of malaria throughout the year, as educational and enforcement measures became more and more effective.

    Head nets, gloves, and leggings were prescribed for all guards and sentries on night duty. Between the hours of 1800 and 0630, antimosquito lotion was prescribed for all individuals visiting or passing through unsanitated areas. Mosquito bars were required in all table of organization type barracks even though there were screens. Kitchens, messhalls, and recreation halls were

sprayed twice daily, at the same hours as the barracks. Motion picture theaters were sprayed between 0600 and 0700 and again before the start of the first performance.

TABLE 23.-   Malaria rates of primary and recurrent cases among U.S. Army personnel, Panama Canal Department, by month, 1943

    Primary malaria in unsanitated areas, however, continued to show a rate more than twice as high as in sanitated areas. Recurrent malaria was always present, due chiefly to turnover in personnel. Chronic relapses occurred among Puerto Rican troops, then replacing continental units in the Panama Canal Department.

    The conquest continued with increasing success through 1944 (table 24).

TABLE 24 .- Malaria rates of primary and recurrent cases among U.S. Army personnel, Panama Canal Department, by month, 1944

    The inevitable seasonal fluctuations are still present, but the improvement over the previous year is evident at a glance.

    One new, routine procedure adopted in 1944 was the spraying of screens in unsanitated areas with residual DDT. Also, water that could not be eliminated by filling or ditching was treated with a 5 percent solution of DDT in a 4 to 1 mixture of diesel oil and grade "c" fuel oil.

    Malaria discipline was carried to greater efficiency than in 1943. The combined rate for primary and recurrent malaria for the year 1944 was reported as 14.5.

    In 1945, the malaria rate fell still lower. The rate per thousand per annum for primary malaria became 5.8, for recurrent malaria, 3.4. The total rate, 9.2, was the lowest yet attained in the PCD, and it was the first time, since the PCD was established, that the rate among troops was lower than the rate for the Panama Canal (table 25).

TABLE 25 .- Malaria rates of primary and recurrent cases among U.S. Army personnel, Panama Canal Department, by month, 1945

    It will be seen that seasonal peaks, though real, are without arresting significance.

    Control measures remained much the same in nature as before. Filed reports refer to spraying all screens and screen doors as well as the interiors of occupied buildings, with monthly applications of 5 percent DDT in diesel oil. Freon-Aerosol dispensers were reserved for use in the destruction of adult mosquitoes.

    At this time, responsibility was efficiently vested in three levels of authority. Each organization looked out for maintenance of buildings and drainage control in its own area. In all areas not maintained by organizations, the post engineers, working in cooperation with the Medical Department Field

Sanitary Force, constructed and maintained malaria control installations. The long-range (10-year) program was the responsibility of the Department engineer. Malaria control continued to be a "command responsibility."

    The fact that the December rate tops that of May and June deserves special explanation. Malaria discipline is easiest to maintain when privileges are few. Thus, in the PCD, an exceptionally high standard prevailed during the first 10 months of 1945; however, as the rates for both primary and recurrent malaria remained law or went lower, it became increasingly difficult to enforce malaria discipline. The constant example of stricken comrades was lacking, and the men began to feel that the danger had been exaggerated. When no malaria occurred in an organization for several consecutive months, some relaxation of discipline was sure to follow. A real slump came during the last 3 months of 1945, when overnight and weekend passes were again instituted. Added to the usual increase of anophelines at the end of the dry season, this resulted naturally in an increase of primary malaria for December 1945.

    A renewed emphasis on the instructional program followed. All men going on pass were instructed to use the issued repellents. It is greatly to the credit of both medical and line officers, commissioned and noncommissioned, that a "high sense of moral responsibility" was maintained. One report contains the comment: "Men free for the night wander far afield and when in certain environments cease to consider the dangers of malaria."

    Recapitulation and comment.- Rather complete statistics are available for the Panama Canal Department regarding malaria cases over a period of years. Table 26 includes both primary and recurrent malaria among military personnel and represents the number of cases per annum per thousand average strength admitted to medical treatment facilities.

TABLE 26 . - Attack rates for malaria among U.S. Army personnel, Panama Canal Department, 1936-45

    The relatively low rate for 1939 shows the effect of a consistent effort at control over a 4-year period, under rather stabilized conditions insofar as troop movements were concerned. The expansion of activities during the next 3-year period, involving as it did the establishment of small outposts, emergency airfields, and the like, away from sanitated bases, found reflection in the rather alarming increase in 1942, when the rate was more than double that of the

previous year. Another factor was the influx of new troops who had no experience in dealing with malaria.

    During the next 3 years, a full-scale control program was in operation, in which all available methods were employed. The results speak for themselves. Part of the decline in rate was of course due to the gradual abandonment of many minor outposts. On the other hand, the control program was sometimes handicapped by delays in delivery of insecticides and repellents because the Quartermaster was under obligation to meet the greater demands, in the far Pacific and elsewhere, which had first priority.

    It is of interest to note that, during the latter half of 1942, the malaria rate for Panama Division employees of the Engineer Service, Caribbean Defense Command, was only 52.52; ⁵⁹ undesirably high, of course, but less than half the rate for PCD military personnel.⁶⁰ The wide dispersal of the latter as compared with the relatively fixed location of the labor camps was presumably a factor.

    The story of malaria in the PCD is also reflected in statistics from Gorgas Hospital, Ancon, C.Z., over a 3-year period. During 1942, this hospital handled 4,519 cases of malaria, which represented 13.2 percent of its total caseload. In 1943, the figure stood at 1,843, or 6.0 percent of all cases treated. In 1944, there was a still further reduction to 1,071, or 4.6 percent. These percentages represent actual diagnosis of malaria by blood smear.

Special Units, Organizations, and Projects

Field Sanitary Force

    An important factor in keeping the malaria situation well in hand was the Medical Department Field Sanitary Force, also called the Field Sanitation Force. This organization, composed of civilian personnel, was especially efficient in carrying out malaria control measures in and about military areas. Such a statement is all the more significant when one realizes that the total strength of this unit in 1942 consisted of 3 sanitary inspectors and an average of 207 laborers (increased subsequently to 251).

    The Field Sanitary Force was established in 1939 by the Office of the Surgeon, Panama Canal Department, and was made up largely of men from the West Indies, particularly from the island of Martinique.

    Toward the end of the war, Panamanians came to predominate in the labor gangs, with the remaining West Indians serving as the backbone of the Force.

⁵⁹ Letter, Lt. Col. S. J. Lerro, MC, Chief Surgeon, Panama Division, Engineer Service, Caribbean Defense Command, to The Surgeon General, U.S. Army, 30 Jan. 1943, subject: Medical History of the Panama Division, Engineer Service, Caribbean Defense Command. 1941-1942.
⁶⁰ (1) In 1906, the malaria death rate for employees of the Panama Canal and Panama Railroad was 745 per 100,000. Morbidity ran much higher, 82.1 percent of all employees being admitted to dispensaries and hospitals. By 1916, admissions had dropped to 1.6 percent and the death rate was 6 per 100,000. In 1942, the malaria rate rose to 2.45 percent, but was soon reduced again, and for 1945 stood at 1.26 percent. (2) Faust, Ernest Carroll: Malaria Incidence in North America.  In Malariology, edited by Mark F. Boyd. Philadelphia: W. B. Saunders Co., 1949, vol. I, pp. 749-763.

    Working in close cooperation with the Field Sanitary Force was Maj. (later Lt. Col.) George W. Hamilton, SnC, who made the drainage survey for malaria control throughout the posts and outlying areas. Working both in office and field was Capt. Emery V. Smith, MC, assistant malaria control officer for the Department.

    In 1946, the Field Sanitary Force was still engaged in control activities at airbases and subbases of the Caribbean Air Command, though with reduced personnel.

Army School of Malariology

    Facilities for training specialized personnel had come into being at several points in response to pressing needs. Cooperating in these preliminary enterprises were the Tennessee Valley Authority, the Florida State Board of Health, the Rockefeller Foundation, and the Pan-American Highway Commission. The Army used these various facilities for training military personnel, but the scattered location of the training areas made instruction difficult and much time was lost in moving from place to place. The Surgeon Generals Office finally succeeded in unifying these efforts through the establishment, at Fort Clayton, C.Z., of the Army School of Malariology.

    Activation took place on 26 January 1944. Original authorized strength was 10 officers and 14 enlisted men, but this was increased on 1 April 1944 under Special Manning Table 8-40-PC to 11 officers and 49 enlisted men. Col. Charles G. Souder, MC, was appointed commandant.

    Dr. John E. Elmendorf, Jr., of the International Health Division, Rockefeller Foundation, who had served 2 years as director of the Florida school, became assistant commandant.

    The mission of the school was to train officers and units in Army methods of controlling malaria in endemic areas. To be eligible for training, Medical Corps officers were first required to complete a course in tropical medicine. Sanitary Corps officers (parasitologists, entomologists, and engineers) were especially selected by The Surgeon General. Enlisted men (from malaria control and malaria survey units) were carefully selected on the basis of their qualifications. Laboratory technicians were also trained. Officers were trained in groups of 25 to 30.

    The course, which was of 4 weeks' duration, was designed to present actual problems and practical exercises in malaria control (fig. 26). Night operations were included as part of the instruction.

    The staff, as constituted in July 1944, consisted of ten commissioned officers, including a clinical malariologist (Dr. Elmendorf), an entomologist, and a sanitary engineer, each with the rank of lieutenant colonel. An entomologist and a sanitary engineer, each with the rank of major, were also provided in the table of organization: The enlisted personnel included seven technical sergeants of whom three served as instructors in entomology and one in parasitology. In the grade of private there were also three instructors in entomol-

FIGURE 26.- Parasitology class, Army School of Malariology.

ogy and one in parasitology. The author personally attests that these eight enlisted instructors, carried as "sanitary technicians," did yeoman service. Most of these men had received civilian education equivalent to that usually found in commissioned personnel.

Experimental work under military auspices

    Protective clothing .- Considerable attention was given to penetrability of cloth to the bites of disease-carrying mosquitoes. Byrd cloth, as tested against A. albimanus and Aedes aegypti, gave best results. If arm tests of any particular fabric showed that the latter permitted penetration either in the dry or wet condition, or when soaked with sweat, that fabric was discarded. The lasting quality of any fabric, under jungle conditions was, of course, considered of major importance.

    It was recommended that any uniform designed primarily for protection against mosquito bites should be larger than ordinary and loose fitting. (Even so, the discomfort from lack of ventilation can be considerable.) No mosquito-proof garment was intended to replace repellents or malaria discipline in general, but rather to be used in combination with them.

    Experiments utilizing DDT. - On 10 September 1943, Colonel Cox was sent 5 pounds of Gesarol (DDT) by air express, for trial use as a larvicide. Fifty pounds followed by ordinary shipment. Crankcase oil, also diesel oil No. 2, had been recommended as vehicles for application. This was the begin-

ning of a series of field experiments, which led finally to large-scale treatment of extensive areas by airplane. Certain aspects of these experiments and field trials are summarized in paragraphs which follow:

    The first significant studies on the experimental use of DDT as a larvicide were reported early in 1944. The following points seemed especially important:⁶¹ (1) The new insecticide killed all larvae, both Anopheles and Culex, as determined by examination 24 hours after application (none of the control oils achieved this); (2) a 1-percent concentration ( ¹ /100 of a pound per acre) was quite as effective against mosquito larvae as a 5-percent concentration (¹/20 of a pound per acre) (the stronger concentration was detrimental to fish and vegetation, while the 1-percent concentration appeared not to be) ; and (3) the lasting power of the larvicidal mixture is related to the character of the diluent and the method of application. Thus, a viscous oil mixture, distributed through marginal vegetation with a mop had a more enduring effect than a light oil mixture, applied with a knapsack sprayer. In the former case, a persistent film is renewed from the reservoir established at the margin. In impounded waters, such applications controlled anopheline breeding for 4 weeks.

    Possible disadvantages were also noted: (1) Heating is necessary to put DDT into complete solution, especially with the higher viscosity oils, and (2) the 1-percent concentration killed practically all forms of insect life in the water. Since this included adult mosquitoes alighting on the water for oviposition, malaria control was augmented, but the destruction of many forms of fishfood might well have adverse economic effects. From a strictly military standpoint, this was not of immediate concern, but, in the interest of long-range conservation, it was destined to have a limiting effect on the general use of DDT in postwar years.

    All of the field work, in connection with the tests described previously, was carried out by Capt. Emery V. Smith.

    During the calendar year 1944, two reports were rendered on the hand application of DDT as a larvicide, and three on the distribution of DDT by airplane. Hand application related almost entirely to larviciding, but treatment from the air was aimed at control of adult mosquitoes as well. Toward the end of the year, a specially constituted board of officers, including Navy personnel, made preliminary tests on the efficiency of a 20-percent solution of DDT by weight in "Velsicol NR 70," distributed as an Aerosol spray by a specially equipped combat aircraft furnished by the Navy. Tests scheduled for 1945 included large-scale distribution of DDT in various solvents by multi-engined aircraft of the C-47 and B-25 type.

    Various boards were appointed, augmented, modified, and superseded in the course of this work. It is not practical to list them all. A selected example will serve to illustrate procedure:

⁶¹Letter, Col. Wesley C. Cox, Mc, Surgeon, Panama Canal Department, to The Surgeon General, U.S. Army, 2 Feb. 1944, subject: Report on Efficacy of a New Larvicide (DDT), inclosure thereto, 15 Jan. 1944, subject: Observations and Comment on the Efficacy of New Larvicide and Some Methods of Application.

    In January 1945, a board of officers was appointed to study certain aspects of malaria control. ⁶² The personnel were as follows: Col. Charles G. Souder, MC, Army School of Malariology (Chairman); Col. Wesley C. Cox, MC, Headquarters, Panama Canal Department; Col. Harold E. Schneider, MC, Sixth Air Force; Lt. Col. Daniel Bergsma, MC, Headquarters, Caribbean Defense Command; Lt. Col. Alton H. Saxer, MC, Sixth Air Force; Maj. (later Lt. Col.) Charles L. Pierce, SnC, Panama Canal; Maj. Marshall Hertig, SnC, Gorgas Memorial Laboratory; Capt. Emery V. Smith, MC, Headquarters, Panama Canal Department, Recorder; and Dr. Herbert Clark, Director, Gorgas Memorial Laboratory.

    Three technical consultants were also designated: Lt. Col. (later Col.) John Q. A. Daniels, MC, Maj. Tristram J. Cummins, Jr., CWS, and Capt. William N. Sullivan, SnC.

    Included in the objectives of this study ⁶³ were: (1) Action of various solutions of DDT against larvae and adult mosquitoes; (2) effectiveness of equipment devised for aerial distribution of DDT; (3) securing of information relative to the influence of terrain, meteorological conditions, type of equipment, and other factors on effectiveness of DDT; and (4) the effect of DDT on insects other than mosquitoes.

    A preliminary report was rendered 31 March 1945 on tests carried out in the Republic of Panama between 23 January and 6 March 1945.

    Certain aspects of DDT airplane spraying tests in Panama are summarized from a report by Lt. Col. Oliver R. McCoy, MC:⁶⁴

    The Army Air Forces Board arrived in Panama, 23 January 1945. These officers, from Wright Field, Ohio, and Orlando Air Base, Fla., were accompanied by five civilian consultants; four of these consultants were from the U.S. Department of Agriculture. These were assigned by a special board appointed by the surgeon of the Caribbean Defense Command. Colonel Cox served as project director.

    Two malaria control units, 30 Medical Department enlisted men, and 12 enlisted men from the Army School of Malariology assisted in the work.

    The Signal Corps set up a communications system and furnished photographers. A complete weather station was established at field headquarters.

    The Army Air Forces Board took charge of application. The Panama Board evaluated results. Five plots in a jungle area east of Panama City

⁶² Letter, Col. Hugh 1. Deeney, AGD, Adjutant General. Office of the Department Commander, Headquarters, Panama Canal Department, to Col. Charles G. Souder, MC, Army School of Malariology (Chairman) and members of a Board of Officers, 23 Jan. 1945, subject: Appointment of Board of Officers to Study Certain Aspects of Malaria Control.
⁶³ Report, Col. Charles G. Souder MC, Chairman, Board of Officers, to The Commanding General, Panama Canal Department, 31 Mar. 1945, subject: Preliminary Report of a Board of Officers Appointed to Study Certain Aspects of Malaria Control.
⁶⁴ Memorandum, Lt. Col. O. R. McCoy, Mc, Director, Tropical Disease Control Division, Preventive Medicine Service, Office of The Surgeon General, U.S. Army, to Acting Chief, Preventive Medicine Service. Surgeon General's Office, 19 Feb. 1945, subject: Observations of DDT Airplane Spraying Tests in Panama.

were surveyed by the Corps of Engineers, and perimeter and diagonal trails were provided. Covering vegetation was about 100 feet above the ground. Preliminary mosquito counts were made from human bait at 20 stations in each plot and from a horse trap set in the center of each.

    Almost complete elimination of adult mosquitoes was accomplished in all the areas treated. Larvicidal effects were tested by setting out pans of water containing Aedes larvae at ten points in each plot. Since A. albimanus larvae do not survive transportation, these were tested by exposure in the laboratory to water rendered toxic in the field. The larval kill depended on whether or not the spray penetrated the jungle covering.

    The number and size of spray particles reaching the ground were determined by setting out slides, coated with magnesium oxide, at each station. From 1 to 5 percent of the material reached ground level.

    Four plots were variously treated, using a variety of solvents. One plot was left untreated, as a control. All spraying was done between 0725 and 0745 hours, a period when there was little or no wind. The plane used was a B-25 (J) equipped with a grid outlet. Results indicated that this type of equipment was more satisfactory than any yet developed for spraying DDT in the field.  Comparisons with exhaust Aerosol type of apparatus had not as yet been made.

    Army Air Forces Board Project No. F-4095 was completed and reported on 11 April 1945. Large payload type aircraft had been used and various DDT solutions employed. These tests made use of a lake, a jungle area, two native villages, and six jungle test plots, all similar.

    On 17 March 1945, a special board of officers was created to study further certain aspects of the problem. This board included four officers from the Sixth Air Force.

    Using a C-47 plane with a carrying capacity of 800 gallons of DDT in diesel oil, the group conducted numerous tests in four distinct areas: (1) The Chilibre-Buenos Aires area, involving a river, lake and jungle area, (2) the Farfan swamp area, and (3) the old French Canal area.

    Toward the end of the year, a special study was begun, involving four villages situated along the Atlantic coast, west of Fort Sherman, C. Z. All four were known as hyperendemic foci of malaria. The inhabitants of Piña were treated each week with the experimental drug SN 7,618 (chloroquine diphosphate). In Lagarto, the houses were sprayed or painted with a 5-percent solution of DDT in diesel oil. The village of Salud was sprayed from the air with the same preparation. Nuevo Chagres was left untreated, as a control. An expansion of this program was later put into effect.

The Gorgas Memorial Laboratory

    Through the National Research Council and the Office of Scientific Research and Development, a number of problems relating to insect vectorship of disease were studied at various locations. Three projects of prime im-

portance in the control of malaria were: (1) The development of insect repellents; (2) the development of efficient insecticides other than pyrethrum; and (3) the development of improved larvicides for the control of anopheline mosquito breeding.⁶⁵

    The Gorgas Memorial Laboratory, in the Republic of Panama, was in a favorable location for this type of work, not only because of climate and terrain but also because cooperation for military field studies was assured from the Panama Canal Department.

    By memorandum of 24 April 1943, four Sanitary Corps officers were allotted for duty with The Surgeon General for the purpose of conducting these and other researches at the Gorgas Memorial Laboratory.⁶⁶

    Dr. Herbert C. Clark, Director of the Laboratory, acted as commanding officer of the group. The Army personnel, with dates of arrival and departures, were as follows: ⁶⁷

Personnel and date of arrival                                                             Status of 1 November 1945
Maj. Marshall Hertig, 15 June 1943....................................................Still on duty.
1st Lt. (later Capt. Alexander G. B. Fairchild, 8 April 1943.................Still on duty.
1st Lt. (later Capt.) William C. McDuffie, 16 August 1943..................Departed 11 June 1944.
1st Lt. (later Capt.) Roy Melvin, 4 October 1943................................Departed 10 September 1944.
2d Lt. (later 1st Lt.) Harold Trapido, 4 July 1944................................Still on duty.
1st Lt. Charles D. Michener, 15 December 1944................................Still on duty.
T/4 Edson F. Fichter, 17 July 1944.....................................................Departed 20 October 1944

    It will he seen that the allotted strength of four officers, including one of field grade, was maintained throughout the period concerned. Capt.( later Maj.) Alexander G. B. Fairchild, SnC, had been a staff member of the Gorgas Memorial Laboratory for 5 years previous to his military duty. Capt. Roy Melvin and Lt. Charles D. Michener, who replaced him, were concerned with studies on chiggers. The DDT anopheline projects were directed by Capt. William C. McDuffie. His successor, 2d Lt.. (later 1st Lt.) Harold Trapido, was chiefly concerned with the village malaria control project.

    The headquarters of the unit were located in the Gorgas Memorial Laboratory in Panama City. The Institutes animal houses, the insectary with its colony of A. albimanus, and the services of laboratory personnel were likewise available for use.

    In addition, the field station at Juan Mina, on the Chagres River just inside the Canal Zone boundary, was much used. Most of the repellent tests, the DDT anopheline work, and the village DDT spraying project were carried out from this point.

⁶⁵ Memorandum, Col. J. R. Hudnall, Mc, Director, Military Personnel, [Office of The Surgeon General,] to The Director, Military Personnel Division, Army Service Forces, 13 Apr. 1943, subject: Allotment of Officers to The Surgeon General for a Special Duty.
⁶⁶ Memorandum, Brig. Gen. Russell B. Reynolds, GSC, Director, Military Personnel Division, Army Service Forces, for The Surgeon General, 24 Apr. 1943, subject: Allotment of Officers.
⁶⁷ Hertig, Marshall: Chronological History, Gorgas Memorial Laboratory Unit of Sanitary Corps Officers, 1943-45. [Official record.]

    The expenses of the units various projects were covered partly by the Gorgas Memorial Laboratory and partly by funds provided under contracts between the Laboratory and the Committee on Medical Research of the Office of Scientific Research and Development. Certain supplies were furnished by the Army, as were two vehicles (but not their maintenance).

    Helpful contacts were maintained with the chief health officer of the Panama Canal, the surgeon of the PCD, and the surgeon of the Panama Mobile Force. This gave opportunity for the officers of the unit to visit field installations and jungle outposts and to participate, with troops, in field tests of repellents and protective clothing.

    Repellents Rutgers 612 dimethyl phthalate, and the Army's 6-2-2 mixture were tested against A. albimanus, A. triannulatus, and four species of Mansonia. All were found effective against both anophelines and culicines.

    Early experiments with DDT dusts as larvicides were not encouraging, and emphasis was shifted to oil solutions and emulsions. It was brought out that since the effect of DDT in oil as a larvicide is very brief, its principal value lies in the practically 100 percent kill which can be achieved with very small quantities of the insecticide, such as one-fortieth to one-twentieth of a pound per acre.

    Major Hertig and Captain Fairchild, as members of the board of officers serving under Colonel Souder, participated in the experiments on spraying DDT from aircraft under jungle conditions. Dr. Herbert Clark and members of the U.S. Department of Agriculture, Bureau of Entomology and Plant Quarantine, from Orlando, Fla., and Washington, D.C., also served with this group.

    Captain McDuffie carried out experiments in half-acre plots to determine the effects of DDT sprayed from the ground to control adult mosquitoes. In dense jungle, the beneficial effect lasted several days, while in open country the benefit was transient. The latter observation was supported by the subsequent work of Captain Fairchild in a cacao plantation at Almirante, Republic of Panama, where no effect was observable the day after spraying was carried out.

    The village spraying projects conducted by Lieutenant Trapido deserves special comment. In 15 months of investigational work, he demonstrated the desirable effect of merely spraying the houses, which were built of cane walls with palm-thatched roofs. ⁶⁸ There is obviously no way to render such dwellings mosquitoproof. Five percent DDT in kerosene was applied inside and out at intervals of 4 months to houses in the village of Gatuncillo, in the middle Chagres River area. Two adjacent villages were used as controls.

    As measured by house catches and horse baited traps, a great reduction of anophelines was realized in the treated village and area close by. The degree of control improved with successive treatments. During the third 4-month

⁶⁸ Trapido, H.: The Residual Spraying of Dwellings with DDT in the control of Malaria Transmission in Panama, With Special Reference to Anopheles albimanus . Amer. J. Trop. Med. 26 : 383-415, July 1946.

period, the malaria transmission potential, as shown by captured A. albimanus, was reduced by 99.9 percent. Reduction in anopheline population was evident for at least 300 feet into the forest. At the end of the first year, a decrease of the malaria rate was also observed. ⁶⁹

    Earlier work on projects sponsored by the Office of Scientific Research and Development had been carried on by Dr. Carl M. Johnson who studied malaria antigens and by Mr. Daniel M. Jobbins who investigated insect repellents.⁷⁰

    It should be remembered that much of the knowledge that was available concerning malaria in Panama at the outbreak of the war was the result of surveys and investigations carried on by the staff of the Gorgas Memorial Laboratory. The tenth and final report on a selected group of villages along the Chagres River was published in 1941.⁷¹ Species of malaria parasites were found in the following proportions: P. falciparum, 72 percent; P. vivax, 22 percent; and P. malariae, 6 percent. More than half the population of the villages studied were positive for malaria one or more times during the year as shown by monthly surveys. Significant in the general findings is the conclusion that drug treatment, though it practically eliminates severe clinical malaria, cannot prevent an epidemic when unusually great numbers of the vector are present. It is, therefore, considered quite impossible to eradicate malaria parasites by such means, or even to reduce transmission to any great extent. It was established that quinine and Atabrine may be considered equally effective as antimalarial drugs but that the use of Plasmochin (pamaquine naphthoate), because of its toxic effects, requires close supervision.

The Pan American Highway

    Along the Inter-American Highway, especially in Central America, the most important malaria vector is A. albimanus, with A. pseudopunctipennis a secondary vector at high altitudes.⁷² From both a military and a civilian standpoint, it is important that halting places for travelers be made as safe as possible. Routine measures that render the large centers of population more or less mosquito free are not practiced in the smaller towns of the rural lowlands, which, therefore, remain a special hazard in this respect. Surveys begun in 1943 by the Pan-American Sanitary Bureau showed that the risk of contracting malaria exists for the most part below an altitude of 1,000 feet

⁶⁹ In recent years, a degree of resistance on the part of the anophelines has been reported. This has proved to be due to a change of resting habits, whereby the mosquitoes no longer seek walls of buildings for resting purposes, and thus tend to avoid contact with the treated surfaces. True, physiological resistance, as in the housefly, has not been confirmed. - L.S.W.
⁷⁰ Letter, Henry E. Meleney, M.D., Consultant to the Secretary of War, to Members of the Central American Commission on Field Instruction in Tropical Medicine, 7 Apr. 1943, inclosure thereto, subject, Report of Tour of Central America For the Purpose of Surveying Tropical Diseases Conditions and Opportunities for Field Experience in Tropical Medicine.
⁷¹ Clark, H. C., Komp, W. H. W., and Jobbins, D. M.: A Tenth Year's Observation on Malaria in Panama, with Reference to the Occurrence of Variations in the Parasite Index, during Continued Treatment with Atabrine and Plasmochin. Am. J. Trop. Med. 21: 191-216, March 1941.
⁷³ Jobbins, D. M.: Algunos problemas en el control de mosquitos en la carretera interamericana de Centro América. Bol. Ofic. san. Panam. 27: 819-826, September 1948.

and that only very restricted malaria centers exist above 3,000 feet. These isolated foci at higher altitudes did, however, increase in number during the construction period, because the infected laborers served as malaria reservoirs after returning home.

    International conferences relative to the construction of an Inter-American Highway date from l923. ⁷³ Appropriations by the U.S. Congress began in 1925. The military value of the project was recognized after the bombing of Pearl Harbor, and on recommendation of Gen. Brehon B. Somervell, Commanding General, Army Service Forces, the War Department took over the responsibility of construction in Central American countries on 3 July 1942. Col. Edwin C. Kelton of the Corps of Engineers was placed in charge, with instructions to make the highway passable for heavy military traffic, in all weather, from the northern border of Mexico to the Canal Zone. This involved 459.7 miles of new construction, in addition to the improvement of 404 miles of existing road; 696 miles of all-weather road were already in use. When the project was discontinued for military purposes on 31 October 1943, approximately 600 additional miles had been made passable, with some 233 miles of road in Panama and Costa Rica still be to constructed. It should be pointed out that at no time was the completion of the project considered an urgent military necessity. It, therefore, received a very low priority both as to materials and shipping facilities.

    The mileage to be constructed or improved under Army supervision was constituted as follows:

                                                                                                                                Mileage
David, Panama, to LaConcepcion, Panama ...............................................................   15.0
La Cuesta to Piedras, Panama, to San Isidro del General, Costa Rica......................... 129.8
San Ramon, Costa Rica, to Nicaraguan border........................................................... 150.3
Nicaraguan-Costa Rican boundary to Diriamba, Nicaragua..........................................  64.5
Sebaco, Nicaragua, to Honduran border.....................................................................   82.3
Honduras-Nicaragua boundary to Goascaran River on Salvador-Honduras border......   91.8
Goascaran River to San Miguel, Salvador...................................................................   36.0
San Christobal, Salvador, to Guatemala City............................................................... 100.0
Guatemala City to Mexican border.............................................................................  194.0

Total..........................................................................................................................  863.7

    Approximately 27,000 persons were employed by contractors and U.S. engineers. Of these 25,060 were Central American natives.

    At the beginning of the project, Colonel Kelton requested that two officers from the Medical Corps be assigned for duty with his group, one to serve at San José, Costa Rica, the other at Managua, Nicaragua. At the time, it was contemplated that approximately 120 men would be stationed in panama and Costa Rica, 100 in Nicaragua and Honduras. The total allotment of officers was accordingly increased by this number, and two medical officers of the rank of major, experienced in tropical diseases, were ordered to Headquar-

⁷³ The Inter-American Highway, an Interim Report from the Committee on Roads, House of Representatives, U.S. Congress, 18 Dec. 1946.

ters, Pan American Highway, U.S. Engineer Office, Los Angeles, Calif., for duty in Central America.

    A list of medical installations eventually utilized or established in connection with the project is shown in table 27.

TABLE 27.- Medical installations, Pan American Highway

    Besides the officers assigned to Central American duty for the duration of the project, several others served the area on a temporary basis. Through the efforts of Col. (later Brig. Gen.) Leon A. Fox, MC, it was suggested that a limited number of medical officers, who had completed a course in tropical

medicine, should be assigned to the area temporarily, for the dual purpose of serving the organization and gaining personal experience in the handling of tropical diseases.

    This was made operative in March 1943: as a result, nine officers, selected by The Surgeon General, reported to the project medical director and were stationed at construction camps and other points where training facilities were suitable. By a system of rotation, each officer trainee was brought into contact with all tropical diseases and sanitary problems related to the project.

    Climatological factors affected both engineering and health problems. In Central America, as stated previously, there is usually a wet and a dry season. As a rule, the dry season begins about the first of December and terminates in May. The rainy season of 1942 proved abnormally wet and long, in some localities extending to February 1943. By contrast, the rainy season of 1943 was abnormally dry.

    In most years, western Panama and south Costa Rica receive a heavy rainfall. Toward the north and west, this diminishes, with Nicaragua and Honduras receiving the minimum. There is then a gradual increase through El Salvador and eastern Guatemala. In western Guatemala, heavy precipitation is the rule.

    In general, the wet season is favorable to mosquito breeding throughout Central America. The heavy rains are not handled adequately by the drainage channels which effect control at other times, and fresh breeding places are thus created. By contrast, the dry season is unfavorable to adult mosquitoes and, though breeding goes on, the average female rarely survives long enough to become infected.

    Early attention to malaria prevention was inclined to be haphazard. Dr. Henry E. Meleney, ⁷⁴ Consultant to the Secretary of War, made an extensive tour of the Central American countries in 1943. In Costa Rica, at a new camp and hospital for Army engineers near Esparta, he found screen doors of mess-halls opening inward and mosquitoproofing of buildings incomplete. At a similar camp near Las Cañas, he found windows of sleeping quarters furnished with shutters but not with screens. Gauze was used on doors instead of wire screens, and some doors had no springs; however, mosquito bars were in use.

    Based on recommendation of the Pan-American Sanitary Bureau, protective sanitary measures were instituted in construction camps along the highway, particularly, in Nicaragua and Costa Rica. In Costa Rica, from 12 to 40 percent of all time lost by American labor had been traced to malaria. Ditching and the use of oil larvicides were emphasized.

    In Nicaragua, DDT was used both as a larvicide for the spraying of buildings in the larger, newer camps along the Rama Road. This road branches from the Pan American Highway near Lake Managua and Lake Nicaragua and proceeds to the Atlantic Coast. Certain camps in Honduras received similar treatment. In all cases, control was adequate.

⁷⁴ See footnote 70, p.192

    In the smaller, temporary camps, where expenditures for drainage could not be justified, larviciding, together with spraying and screening of barracks, gave reasonable control.

   A special aspect of the problem was related to the large number of imported laborers who proved to be malaria carriers. Treatment was instituted, not only for those with symptoms, but for all carriers who could be discovered.

    The malaria situation as of 30 June 1943 is well set forth in a letter from Colonel Kelton to the Chief of Engineers, U.S. Army.⁷⁵ The plan of medical care had been developed in accordance with recommendations of Colonel Fox who, acting for the Office of The Surgeon General, conducted a survey of medical conditions in November 1942.

    The administration of the Pan American Highway in Central America operated as two units. The northern area, with headquarters at Managua, Nicaragua, included Guatemala, El Salvador, Honduras, and Nicaragua. The southern, or San José area, which included Costa Rica and Panama, was administered from San José, Costa Rica. The chief medical officer, who maintained headquarters at San José, had assigned to his staff one officer trained in entomology and malaria control, also a sanitary engineer, similarly specialized.

    All personnel stationed in malarious areas were required to sleep under bed nets, but screening for barracks and messhalls was not at first available. Until this could be provided, mosquito netting was used in several places to screen messhalls. Citizens of the United States were required to take suppressive Atabrine therapy.

    Local health agencies gave full cooperation in the control program.

    Approximately 375 cases of malaria occurred between July 1942 and June 1943 among the 2,500 U.S. citizens on duty with the Pan American Highway in Central America. This 15 percent, however, occurred in less than half the total personnel, chiefly among those stationed at ports of entry, or on duty in hyperendemic areas, or engaged in survey work. It should also be noted that the worst malaria epidemic in 20 years occurred during this period in the countries concerned. Nicaragua and Honduras suffered most, chiefly because of a great scarcity of antimalarial drugs.

    In the San José area (Costa Rica), employees lost time because of malaria⁷⁶ during every month that the project was in operation. In a period of 10 months, a total of 187 cases (by monthly increments) handicapped progress in this area alone.

Three-million-dollar plan for the Canal Zone

    As mentioned elsewhere, a complete survey of all posts, camps, airbases, and stations within the territorial limits of the Canal Zone was made in 1943.

⁷⁵ Letter, Col. Edwin C. Kelton, Corps of Engineers, Director, Pan American Highway, U.S. Engineer Office, San José, Costa Rica, to The Chief of Engineers, USA, Washington, D.C.. 23 Aug. 1943, subject: Medical Activities, Pan American Highway, Period From Initiation of Project to 23 June 1943.
⁷⁶ Design and Construction of Pan American Highway. Corps of Engineers Historical Monograph, vol. 1, February 1946.

    The resulting maps showed all drainage systems, watercourses, and impounded bodies of water. The recommendations regarding malaria control involved three phases, based on relative urgency.
    1. Projects requiring immediate action, to be completed as soon as possible and in any case within 2 years.
    2. Projects to be completed in the near future, with an outside limit of 5 years.
    3. Long-range projects, requiring completion within 10 years.

    It was estimated that the entire plan would require the expenditure of approximately $3 million. When completed, this would accomplish complete sanitation (with reference to malaria control) for each military installation and its environs within flight range of the anopheline vector.

    Funds for initial operations were made available in 1944, and the Department engineer was instructed to begin work 1 January 1945 on six projects, to meet immediate needs. These included the posts of Corozal, C.Z., Albrook Field, Fort Kobbe, C.Z., Howard Field, France Field, Fort Davis, C.Z., the Chiva Chiva Signal Corps area, and the outlying area of Albrook Field along the Fort Clayton, Corozal, Albrook Highway.

    A sum of $280,000 was expended during the fiscal year 1945 for labor and approximately $120,000 for material. An appropriation of $400,000 was allocated for 1946, and an equal sum was approved for 1947.

    Plans for 1947 included work at Fort Gulick, C.Z., Fort Sherman, Fort Clayton, and the Corozal Cemetery.

    The surveys, on which these projects were based, are models of detail and include specific recommendations as to use of round tile, inverts, and culverts, in addition to showing each location where filling, regrading, and paving should be carried out. ⁷⁷

ANTILLES DEPARTMENT ⁷⁸

Climate, Topography, and Population

    The Greater Antilles and Leeward Islands are generally similar in temperatures. The entire area lies in the belt of the northeasterly trade winds, which makes for an even temperature, ranging between 75º and 95º F. Precipitation may vary greatly, not only from island to island, but from year to year in the same locality. Heat and humidity are not oppressive except in sheltered areas, most of which are some distance from the coast. The "prickly heat season" in Puerto Rico extends from May to September, in typical years. Cuba has a definite rainy season which occurs in June and July. In Puerto

⁷⁷ These surveys and supplementary reports, together with the accompanying maps, appear as Exhibits A, B, and C of volume II, The Prevention of Disease in the U.S. Army During World War II - The Panama Canal Department.
⁷⁸ Except as otherwise indicated, all data in this section have been compiled from the Annual Reports, Medical Department Activities, Antilles Department, 1943-45.

Rico, at coastal levels, January through March are generally very dry, and the fall months are almost always wet. This was sharply reflected in the seasonal distribution of malaria and malarial mosquitoes. In other islands of the group, periods of no precipitation alternate with short periods of local showers. In Saint Croix, rains are rare, and only by drilling deep wells is it possible to obtain fresh water on this island.

    Cuba is the only island with a fertile central plain. Its soil is derived from Laurentian granite, like that of the Appalachian region. The rest of the islands are more or less mountainous, with rather narrow coastal plains. Puerto Rico shows much heavy bodied clay and has a great deal of limerock and granite as well as scattered schist. Although generally semipermeable, its soil becomes highly impermeable where the sodium or saline content is high.

    The relatively porous soils of the remaining islands owe their character largely to having been derived from lava. The role of coral in building these islands has been disputed. Except in the Bahamas, the importance of coral is considered questionable. Salt marshes and fresh water swamps characterize the coastal areas and contribute to mosquito production, with or without malaria.

    Though Cuba and Haiti are somewhat less congested, human population is generally dense in the Caribbean. In most islands, the average is close to a thousand people per square mile. The Negroes, who outnumber the white population perhaps 300 to 1, at least in the past, have tended to be somewhat nomadic, shifting from island to island in small boats. This habit, added to socioeconomic and climatic similarities, has brought about a distribution of disease that is quite uniform throughout the area. Malaria ranks with tuberculosis, syphilis, and enteric infection as diseases of greatest importance. In Haiti. there is a high incidence of yaws.

    With the exception of Cuba, the islands of the Antilles are the eroded tops of mountains or mountain ranges. Malaria was concentrated chiefly in the peripheral coastal plains with inland indentations along stream terraces. Malaria prevalence was greatest in Haiti and Saint Lucia, with the Dominican Republic a close third. These islands, Saint Lucia and Hispaniola, were similar to the three Guianas in this respect. In Puerto Rico and Trinidad, the incidence was somewhat lower but was still sufficient to make malaria a leading cause of death and in all probability the most common disabling illness.⁷⁹ In all eight places mentioned, it was a primary deterrent to economic development. Of the 7 ³/4 million people living in these countries or dependencies, nearly 6 million were concentrated in the more intensely malarious portions.

    Permanent malaria control measures must be extensive in scope, since two of the four common vectors (A. albimanus and the A. aquasalis-A. tarsimacula -

⁷⁹ Henderson, J. M.: A Discussion of Caribbean Malaria Control. J. Nat. Malaria Soc. 4: 189-200, September 1945.

tus complex) breed in a wide range of habitat, including temporary accumulations and saline waters.

    Though rural rates are generally higher than urban rates, the problem is still acute in many principal cities. Lack of planned control by governments, long-effective flight range of certain vectors, abundance of breeding places, and general lack of protection against adult mosquitoes are contributing causes. Costly antilarval measures are economically feasible, however, in urban areas (in terms of per capita cost) whereas, in nonurban districts, they cannot be supported.

    Such was the general background against which military malaria control in the Caribbean was carried to a successful conclusion.

Greater Antilles

    Cuba. - In 1943, Cuba had practically no public health workers on a full-time basis. This tended to slow down any modern program for health improvement, though great strides had been made in the early years of the century, and these gains had not been lost.

    Thus, in 1900, malaria was rampant, the mortality rate being 254 per 100,000 population. A National Department of Health was established in 1909, with a director of cabinet rank, and, by 1913-14, the mortality rate had fallen to 18. There were several epidemics in 1920 and 1934, and mild ones in 1916 and 1926. By 1941, however, the mortality rate was down to 4 per 100,000.⁸⁰

    The disease is endemic in all parts of the island but occurs most frequently in three regions: The valley of the Rio Canto in the province of Oriente, the coastal regions of the province of Pinar del Rio, and the coastal plains of north Camagüey. Plasmodium malariae is rare. In some regions P. vivax and P. falciparum are equally common. In others, P. vivax predominates.

    Five species of anophelines are native, but A. albimanus is the only vector of malaria. It is, however, the most common species. In and about Marianao (near Havana), mosquito breeding had been controlled for some years by the combined efforts of the Health Department and the Rockefeller Foundation. The important U.S. base was located at Batista Field, Cuba.

    Jamaica, B.W.I. - Jamaica, the largest British Island in the West Indies, contains 4,404 square miles, of which about 646 are flat, consisting of alluvium, marl, and swamps. These areas are chiefly coastal. Bluffs, plateau country, and central mountains are encountered in succession as one penetrates the country.

    Public health and medical services are combined in one department, of three divisions, one of which is devoted to communicable disease. Malaria control is included among five subdivisions in this division (1943).⁸¹

⁸⁰ Medical and Sanitary Data on Cuba. Prepared by Medical Intelligence Branch, Preventive Medicine Division, U.S. Army, 20 July 1943.
⁸¹ Report, Maj. H. J. Banton, MC, U.S. Army, subject: Sanitary Survey of the Island of Jamaica, 20-31 May 1941.

    The disease is most prevalent in certain coastal areas but may extend inland up to 2,000 feet. The chief vector is A. albimanus, which is found more abundantly during September, October, and November. Most of the cases of malaria occur between June and January. Areas most productive of the vector are the vicinity of Annotto Bay, Oracabessa Bay, Falmouth, Saint Anns Bay, and Montego Bay.

    In 1940, the island had. 17,441 reported cases of malaria, with 521 deaths, but very few were confirmed with smears. Malaria control followed modern methods but was handicapped by lack of funds. Nine hundred Canadian soldiers brought to North Kingston, in October 1940, used bed nets and repellents but slept in unscreened barracks. Eight cases of malaria occurred in this group within approximately 6 months. ⁸²

    Tests have shown that in Jamaica, if an animal bait trap attracts more than five A. albimanus females per night, a critical concentration exists, and malaria transmission may be expected. During a 3-month period, within which this index was reached, 11 percent of the local people within 2 miles of a certain U.S. military installation reported chills and fever, and four military cases of malaria occurred.⁸³ Aerial spraying of DDT at biweekly intervals corrected the condition. Screening of quarters and proper malaria discipline were continued. It is interesting to note that under similar circumstances the critical A. albimanus index at Losey Field in Puerto Rico was found to be two rather than five; a rather special case.

    American troops were stationed chiefly at Fort Simonds, Jamaica, B.W.I., and at Vernam Field.

    Antimalaria activity here, as elsewhere, was divided into temporary and permanent control. Much of the latter did not get beyond the recommendation stage. The temporary control consisted of oiling small ponds (if not used by cattle for drinking purposes) and other accumulations of water in gullies. Paris green was used chiefly in areas devoted to rice and cane cultivation. The supply of paris green, particularly in 1943, was not always adequate. Beginning in 1944, oil was used only on the post. All extracantonment work was carried out with paris green and lime dust. Chiefly important in the good results achieved was the supervision of extracantonment control work by personnel of MCWA (Malaria Control in War Areas), U.S. Public Health Service. This was essential as three-quarters of the mosquitoes on the post were probably produced outside the base, in canefields and ricefields.

    The routine educational program at Fort Simonds and Vernam Field consisted of lectures to all members of the command, together with special instruction to two members of each unit. There were only two cases in military personnel in 1944, one of which was recurrent. But in spite of this success

⁸² Medical and Sanitary Data on Jamaica and the Clayman Islands. Prepared by Medical Intelligence Division, Preventive Medicine Service, Office of The Surgeon General, U.S. Army, 12 Aug. 1943.
⁸³ Thompson, G. A.: Anopheline Threshold of Malaria Transmission Noted in Jamaica. Pub. Health Rep. 65: 692-695, May 1950.

from a military standpoint, the island still remains dangerously malarious.

    According to Colonial Reports,⁸⁴ there was a sharp outbreak of malaria in the Bull Bay area, 10 miles east of Kingston, early in 1950. During the same year, government hospitals and dispensaries reported a total of 17,896 cases of malaria. The need for cooperation between the U.S. military and island authorities would thus still be very great in the case of any future operations. The Colonial Report for 1946 ⁸⁵ gives 4,011 hospital admissions with 161 deaths, with outpatient attendances for treatment numbering 14,014.

    Haiti (Hispaniola) . - Although the United States did not maintain bases on this island, a few remarks on the malaria situation are in order. According to Caldwell's report on malaria control in the Dominican Republic,⁸⁶ malaria is present everywhere, increasing especially in the spring and fall, when rainfall is greatest. Anopheles albimanus, a versatile breeder, is the principal vector. The malaria work of the government is assisted by the Institute of Inter-American Affairs. Surveys carried out between 1941 and 1944 showed that 0.8 to 38.0 percent of the population have parasites in their blood. Spleen rates, by communities, ranged from 0 to 42.8 percent. In 1,374 positive blood smears, the various types of Plasmodium occurred as follows: P. falciparum, 72.8 percent; P. vivax, 17.2 percent; P. malariae, 4.7 percent; and mixed, 5.3 percent.

    In the Republic of Haiti, recent surveys showed that 86.6 percent of all malarial infections are caused by P. vivax. Mixed infections accounted for 2.6 percent. These included a few triple infections. Three species of anophelines are found, A. albimanus, A. grabhami, and A. vestitipennis.⁸⁷ The first is present everywhere.

    The population is almost entirely Negro and numbers approximately 2 million. No reliable vital statistics are available, but so far as malaria is concerned, clinical manifestations are usually conspicuous only in infants. The higher mountain valleys and the southwest slopes, with scanty rainfall, appear to be malaria free.

    Puerto Rico. - Puerto Rico is an island of approximately 3,534 square miles, with an equable climate and a population of 2.2 million persons. Anopheles albimanus is found everywhere except on the central mountainous ridge. The possibility of eradicating this species has been much discussed. A marked reduction in breeding activity between January and April could perhaps be made the basis for procedure. A campaign, consisting of larviciding and residual spraying for adults, might be started at any point and continued around the island, with the mountains on one flank and the sea on

⁸⁴ Colonial Annual Reports, Jamaica. London: His Majesty's Stationery Office, 1950, pp. 62-63.
⁸⁵ Medical and Sanitary Reports from British Colonies, Protectorates and Dependencies for the years 1939-1941. Jamaica, 1940. Trop. Dis. Bull. 43 (Suppl.): 225-227, 1946.
⁸⁶ Caldwell, J. D.: Malaria control in the Dominican Republic. Puerto Rico J. Pub. Health & Trop. Med. 21: 193-200, December 1945.
⁸⁷ Paul, J. H., and Bellerive, A.: A Malaria Reconnaissance of the Republic of Haiti. J. Nat. Malaria Soc. 6: 41-67, March 1947.

the other. A test program on the smaller island of Vieques has been suggested.⁸⁸

    Puerto Rico, being an American possession, was very naturally the center of military organization and administration for the Antilles Department. The Army had installations at Borinquen Field, Camp Tortuguero, Fort Buchanan, where the Antilles General Depot was located, Fort Brooke, Camp O'Reilly, Losey Field, Henry Barracks, and Fort Bundy,⁸⁹ together with a large number of lesser installations largely for coastal defense or for antiaircraft protection, of which Camp Ensenada Honda may be mentioned as an example.

    The problems of malaria control at these several bases will be treated at some length in the sections which follow.

The Lesser Antilles (Leeward and Windward Islands)

    The Lesser Antilles included the British Windward Islands, the British Leeward Islands, the French West Indies, and the Netherlands West Indies.

    Besides Trinidad and Tobago, the British Windward group includes Barbados, Grenada, Saint Vincent, Saint Lucia, and Dominica. Principal administrative units of the British Leeward group are the British Virgin Islands, Antigua (with Barbuda and Redonda), Montserrat, and Saint Kitts-Nevis (with Anguilla).

    The French West Indian islands consist of two colonies, Martinique and Guadeloupe, with a number of small islands governed as dependencies from the latter.

    The Netherlands West Indies lie in two groups; Curaçao, Aruba, and Bonaire lie off the north coast of Venezuela. The second group is situated to the north of Saint Kitts, in the British Leeward chain, and include Saint Eustatius, Saba, and Saint Martin.

    In a 1943 survey, Barbados was reported free from malaria. Otherwise, the disease was considered to be generally present throughout the Lesser Antilles, with A. albimanus and A. aquasalis serving as the principal vectors.⁹⁰ Malaria is a year-round disease in this part of the world, though most prevalent during and after the rainy season. Blackwater fever has been reported in Martinique and Guadeloupe.

    The Virgin Islands of the United States. - The principal islands are Saint Croix, Saint Thomas, and Saint John. On the island of Saint Croix, the population is largely rural, except for the two small municipalities, Christiansted and Frederiksted. On the island of Saint Thomas, the population

⁸⁸ Henderson, J. M.: The Eradication of Anopheles albimanus in Puerto Rico - an Ecologic Discussion. Mosquito News 8: 45-49; 97-101, June and September 1948.
⁸⁹ History of Medical Department Activities, Antilles Department, Preventive Medicine. [Official record.]
⁹⁰ Medical and Sanitary Data on the Lesser Antilles. Prepared by Medical Intelligence Branch, Preventive Medicine Division, Surgeon General's Office, U.S. Army, 15 Feb. 1943.

centers briefly in the town of Charlotte Amalie. Saint John is sparsely populated.⁹¹

    Malaria occurs usually in the benign, tertian form. The vector is A. albimanus which is widely distributed. Although the U.S. Virgin Islands had suffered epidemic malaria in the 1930's, they were free from indigenous malaria during the war years. The few cases among military personnel were shown to be imported. Only small numbers of A. albimanus were found on Saint Thomas and Saint Croix during surveys conducted in 1944.

    The Army installation on Saint Croix was Benedict Field. Camp Harwood, on the island of Saint Thomas, was a gun position at an elevation of about 1,000 feet. It would have been safe even if a malaria problem had existed elsewhere on the island.

    Antigua. - Because of the early fall of France, U.S. bases and outposts were located chiefly in British (and Netherlands) territory. It is not possible to include detailed information concerning each of the islands where troops were stationed. Antigua, one of the Leeward Islands, and Saint Lucia, one of the Windward group, may be cited as examples:

    The British Island of Antigua has an area of 108 square miles and a population of approximately 35,000. The climate is drier than in most of the West Indies, with an average rainfall of only 43 inches. August through October is the hot, rainy season. Fresh ground water is soon mixed with the sea water which infiltrates the substructure. For this reason, the island suffers from an inadequate water supply.

    Both A. albimanus and A. tarsimaculatus (A. aquasalis) are present. Malaria follows the rainfall. In 1936, when precipitation was 74 inches, there were 3,459 cases of malaria, with 40 deaths. In 1939, when only 33.08 inches of rain fell, the number of cases was 1,173, the number of deaths, 8.⁹²

    The area on Parham Harbour, utilized as a U.S. Army base (Coolidge Field and Antigua Base Command), was at first believed to be in a dangerous location. Winthorpes Village, a Negro village of some 300 inhabitants, jutted into the center of the area on Parham Harbour, from the West. In his 1941 survey, Colonel Fox recommended either that Winthorpes Village be relocated or that U.S. forces be given complete jurisdiction over its sanitation. Careful investigation by John M. Henderson, Sanitary Engineer, (R), of the MCWA, failed, however, to confirm Colonel Fox's suspicions. The daily tidal character of the great mangrove swamp nearby apparently rendered its water unsuitable for any significant breeding of A. albimanus.

    Military communications show very light infection among troops for 1943, during which year the total number of cases was 16. Six of these were primary and ten recurrent., with the probability that the majority of the in-

⁹¹ Medical and Sanitary Data on the Virgin Islands of the United States. Compiled by the Medical Intelligence Branch, Preventive Medicine Division, Office of The Surgeon General, U.S. Army, 26 Oct. 1942.
⁹² Report, Lt. Col. Leon A. Fox, MC, U.S Army, subject: Sanitary Survey of Antigua. British West Indies, 17-21 Feb. 1941.

fections were contracted off the base, which was rather constantly exposed to westerly winds. Main infective areas on the island of Antigua were Freetown, Bethesda, Liberta, Old Road, Urlins, and Johnsons Point. The city of Saint Johns was practically malaria free, in spite of a fairly high percentage of vector anophelines. The British Colonial Government health officer was active in 1944, with engineering projects aimed as mosquito reduction. Military reports for that year listed 10 malaria cases of which 6 were primary and 4 recurrent. All these cases occurred during the first 10 weeks of the year, the majority in newly arrived troops from Puerto Rico.

    Antigua was known to be moderately malarious before it was used as a U.S. base. British reports list 1,450 cases in 1940 and 474 in 1941. In 1941, there were nine deaths. ⁹³

    Saint Lucia . - The British Island of Saint Lucia, 230 miles north of Trinidad, has an area of 233 square miles. It lies approximately midway between Saint Vincent to the south (also British) and the French island of Martinique, which is almost due north.

    Although rough and mountainous, the island is very fertile, and all forms of tropical agriculture thrive. Sugar and other products are exported. The narrow river valleys are subject to great landslides, with occasional economic disaster. Precipitation exceeds 100 inches per annum in the mountainous interior, sometimes decreasing to near 40 at the coast.

    Floods are rare but drought is unknown. The first 4 months of the year tend to be the driest.

    The temperature ranges between 70º and 90º F., and the northeast trade winds are an almost constant influence. At Castries, which has an elevation of approximately 845 feet, the wind direction is so constant that a one-directional airstrip is sufficient.

    Racially, the population is largely Negro or mixed Negro and white. Small numbers of East Indians are found, and still fewer of European descent. Before the onset of the war, malaria had always constituted the main health problem on Saint Lucia and in most years stood higher than all other reported causes of death. ⁹⁴ It doubtless caused more noneffectiveness than all other diseases combined.

    The U.S. Army base at Vieux Fort, likewise the Navy base at Gros Islet., were potentially unhealthy spots. Sixty-five percent of the nearby native population showed malaria parasites, a higher percentage than in any other parts of the island.

    In 1940, according to British reports,⁹⁵ the recorded incidence of malaria showed an upward trend. This was due, it is believed, not to greater prev-

⁹³ Medical and Sanitary Reports from British colonies. Protectorates and Dependencies for the years 1939-1941. Antigua, 1941. Trop. Dis. Bull. 43 (Suppl.) 234-235, 1946.
⁹⁴ Report, Lt. Col. Leon A. Fox, MC, U.S. Army, subject: Sanitary Survey of St. Lucia, British West Indies, 1941.
⁹⁵ Medical and Sanitary Reports from British Colonies, Protectorates and Dependencies for the years 1939-41. St. Lucia, 1940. Trop. Dis. Bull. 43 (Suppl.) : 252-253, 1946.

alence of the disease, but to increased attendance at dispensaries, some of which had just been established. For the year 1940, 11,323 patients were treated at dispensaries and 146 were hospitalized; of these, 6 died. Deaths attributed to malaria throughout Saint Lucia numbered 161.

    Because of this background, it is rather remarkable that the Army construction camp, established in 1941, enjoyed almost complete freedom from malaria. The neighboring town of Vieux Fort had a high malarial rate. The construction camp, however, was to windward of the town; also, early steps were taken to fill Vieux Fort Swamp. This procedure tended to benefit not only Vieux Fort but also the cantonment site, which lay to the northwest. At top development, the construction force numbered about 500 continentals and their dependents, and some 3,000 local laborers. During the first 6 months of operation, there were only four cases of malaria. Saint Urbain Swamp and Coconut Grove continued to breed mosquitoes, but these were not very near the infected areas.⁹⁶ It was reported ⁹⁷ that the malaria rate at Vieux Fort dropped 70 percent over that of previous years as a result of the work of the construction force at Beane Field.

    A real scare was experienced in 1942 when the laboratory reports showed an incidence in military units of 700 per 1,000. This proved to be due to errors on the part of the technician who had interpreted artifacts and blood platelets as malaria parasites.

    The British Government is continuing malaria control work in the Castries District and elsewhere. ⁹⁸

    Guadeloupe .- The French island of Guadeloupe supports three species of anophelines: A. albimanus, A. aquasalis, and A. argyritarsis.⁹⁹ Only A. aquasalis is considered an important vector. It enters houses in great numbers, especially in the evening. The larvae occur in grassy pools, overgrown irrigation channels, rock pools, and flood savannas, all more or less brackish. Anopheles emilianus Komp is considered a synonym.

Trinidad

    This most southerly island of the West Indies lies about 10 degrees north of the equator. It contains over 2,000 square miles. The population is close to 450,000, predominantly Negro. There are at least 150,000 East Indians, and a considerable number of Chinese. The island is very fertile, and the natural resources are great.

    The northern fourth of Trinidad is mountainous. Many streams flow southward, through low, sometimes rolling country. Coastal and inland swamps are numerous. Trade winds serve to mitigate the heat somewhat,

⁹⁶ History of the Caribbean Health Service from Inception to 1 Apr. 1942, St. Lucia.
⁹⁷ Letter, Lt. Col. T. W. E. Christmas, MC, Medical Director, Trinidad District, to the Assistant Chief Health Officer, Caribbean Division, N.Y., 18 May 1942, subject: Malaria Rate at St. Lucia.
⁹⁸ Colonial Annual Reports, St. Lucia. London: His Majesty's Stationery Office, 1948.
⁹⁹ Floch, H., and Abonnenc, B.: Les moustiques de la Guadeloupe. Genre Anopheles . Publ. Inst. Pasteur Guyane No. 108, 1945.

especially between November and May. Precipitation varies greatly, but, in general, the hotter and wetter season extends from May to October, the cooler and drier season from November through April. The annual rainfall at Port of Spain averages 63.66 inches.

    Malaria is the most serious health problem in Trinidad. Up to 1941,¹⁰⁰ there had been no complete malaria survey of the island, but it was known that all types of the disease were present, estivo-autumnal being the most common. Blackwater fever also occurred in sharply defined areas.

    Because of incomplete knowledge, it was recommended that a certain amount of basic research be accomplished before large-scale, expensive control projects should be launched. The Rockefeller Foundation assisted in these investigations.

    Together with Tobago Island, Trinidad boasts 13 species of Anopheles, of which A. aquasalis is the most important vector, with A. bellator the chief transmitter in zones of heavy rainfall.¹⁰¹ As described elsewhere, A. bellator breeds in wild bromeliads which grow attached to branches of the immortelle trees, high off the ground. It should be pointed out that before its vectorship was conclusively demonstrated by Rozeboom and Laird, ¹⁰² Dr. Eric de Verteuil¹⁰³ of Trinidad, in 1934, presented convincing epidemiological evidence that A. bellator was almost certainly a transmitter of malaria.

    Anopheles aquasalis, which favors brackish water swamps is the long-recognized vector along the coast. Both Anopheles neomaculipalpus and A. albitarsis are suspected of being minor vectors. Surveys have shown that A. aquasalis may migrate as much as 5 miles inland, over rough country.

    The main area used by U.S. Army Forces lay 20 miles east of Port of Spain. It included approximately 22 square miles and sloped southward from the foothills. The Army also acquired rights to wharfage in Port of Spain harbor, a recreation area on Saline Bay, and some 2½ square miles of savanna in the west central part of the island. The Navy area was in the extreme northwest. The principal U.S. Army base was Fort Read, Trinidad, B.W.I. including Waller Field. (At times there was autonomous control of the Waller Field area by the Air Corps.) The Antilles General Depot and the Trinidad Subdepot were also located at Fort Read.

Bromeliad malaria still continues to be serious in Trinidad.¹⁰⁴ On the cacao plantations, immortelle trees are planted at rather wide intervals to give desirable shade. In the dry season, these trees lose their leaves. The situation results in more light and less humidity than prevails in the natural forest, so

¹⁰⁰ Report, Lt. Col. Leon A. Fox, MC. U.S. Army, subject: Sanitary Survey of Trinidad, British West Indies, 1941.
¹⁰¹ Stage, H. H., and Gillette, H. P. S. : Observations on Mosquitoes and Malaria Control in the Caribbean Area. Part III - Trinidad. Mosquito News 7: 157-159, December 1947.
¹⁰² Rozeboom, L. E., and Laird, R. L. : Anopheles (Kerteszia) bellator Dyar and Knab as a vector of Malaria in Trinidad, British West Indies. Am. J. Trop. Med. 22: 83, 1942.
¹⁰³ De Verteuil, E. : Administration Report of the Surgeon-General for the Year 1934. Government Printing Office, Port of Spain, Trinidad, British West Indies.
¹⁰⁴ Downs, W. G., and Pittendrigh, C. S.: Bromeliad Malaria in Trinidad, B.W.I. Am. J. Trop Med. 26: 47-66, January 1946.

that A. bellator breeds at lower levels and thus has easy and frequent contact with plantation workers. Although Anopheles breeds in 22 Species of the 30 bromeliads found on immortelle trees, only one species, Gravisia aquilega (which is second in abundance), is of outstanding importance. Surveys showed that this species contained five times as many larvae per tree as any other of 10 species studied. Whereas this might seem to facilitate control, unless workmen are well skilled in discriminating among the species of bromeliads, munch labor can be wasted on the spraying or removal of relatively harmless forms. Wittmackia lingulata and Hohenbergia stellata are usually included in eradication programs because of the close resemblance of the three species.

    Because immortelle trees are dangerous to climb, especially after a rain, the use of phytotoxic sprays has become standard procedure, copper sulfate being the most satisfactory to date. Furthermore, hand removal is more expensive, even with cheap labor. Also, spraying accomplishes far more rapid results. It does not harm the immortelle trees, or the cacaos. One thorough treatment of an area is believed to be sufficient for 5 years. From a long-range standpoint, the replacement of the immortelle trees with windbreak plantings of other species would be a most desirable procedure for discouraging the breeding of A. bellator. At present, this anopheline is scarce in all parts of Trinidad, which has a low rainfall. The highest spleen rates are found in the north-central part of the island, where the annual rainfall is between 91 and 110 inches, and A. bellator the principal, if not the only vector species. Both A. aquasalis and A. neomaculipalpus occur within the region and should be viewed with suspicion.

South American Mainland

    The jurisdiction of the Caribbean Defense Command included Venezuela and the Guianas. The various bases in Brazil pertained to the South Atlantic Command.

    Venezuela .- Venezuela has been thoroughly studied and reported on. The area of the country is 912,050 square kilometers, on which live a little less than 4 million people. The population is described as 20 percent white, 8 percent Negro, 7 percent Indian, and 65 percent of mixed blood.

    The coastal plain, backed by a range of mountains, is called the Costa-Cordillera. Here, 77 percent of the population live on 18 percent of the total land area. South, from the Costa-Cordillera, extends the Llanos. This region, bounded on the south by the Río Orinoco, contains 36 percent of the land area and supports 20 percent of the population. South of the Río Orinoco lies the Guayana., with 46 percent of the land area, but with only 3 percent of the population.

    The rainfall of Venezuela ranges rather uniformly from an average of 39 inches in the north to an average of 79 inches in the south. The wet season occurs near the middle of the year.

    The most malarious region is the Llanos, which contains many rivers subject to flooding, and numerous pools, ponds, and lagoons. Although the Guayana also has many rivers, many of them contain water of such high acidity (low pH) that A. darlingi is prevented from breeding in them.

    All three species of Plasmodium occur. In persons under 5 years of age, P. vivax is found more often than P. falciparum.  Above this age group, the relation is reversed. Infections with P. malariae are relatively few. The annual malaria death rates exhibit a 5-year cycle. Since 1920, these have been more favorable, due to the general improvement in standards of living in the Llanos area. Since 1945, there has been general house spraying with DDT in all areas accessible by car.¹⁰⁵

    Of the 29 species of Anopheles found in Venezuela, only A. albimanus and A. darlingi are considered important vectors, with A. pseudopunctipennis of secondary importance in the mountains. Anopheles darlingi transmits malaria in all three zones, but A. albimanus is a vector only in the Costa-Cordillera. It is less anthropophilic than A. darlingi.

    Entomologists believe that A. albimanus was introduced by shipping, from Central America. ¹⁰⁶ Another possible vector is A. triannulatus which has been found naturally infected with oocysts.¹⁰⁷

    Altitude strongly limits distribution.¹⁰⁸ Thus A. aquasalis, by its preference for brackish waters, is limited to coastal levels. By contrast, A. albimanus ranges up to 1,725 feet, A. darlingi to 2,975 feet, and A. pseudopunctipennis to 3,280. There is considerable adaptability in regard to rainfall. One locality with an annual mean precipitation of 17 inches supports A. albimanus, A. pseudopunctipennis, and A. punctimacula. Yet both A. albimanus and A. punctimacula have been found associated with A. darlingi in an area with an average annual rainfall of 106 inches.

    In Venezuela, the growing of rice creates a special problem in malaria control. Both A. albimanus and A. pseudopunctipennis breed freely in the flooded fields. ¹⁰⁹ The former is the chief and proved vector. La Vectoria suffered a severe outbreak in 1943, and Cagua a similar outbreak in 1944. In the first, no breeding of A. albimanus could be discovered outside of the ricefields; in the second, only 1 percent of the collected larvae were taken from other situations. Shortage of better larvicides reduced control measures to sawdust and kerosene, which did not prove satisfactory. Legislation was eventually passed which forbade cultivation of rice by artificial irrigation near towns, except under permit

¹⁰⁵ Gabaldon, A.: The Nation-wide Campaign Against Malaria in Venezuela. Tr. Roy. Soc. Trop. Med. & Hyg. 43: 113-160, September 1949.
¹⁰⁶ Gabaldon, A., and Cova-Garciá, P.: Zoogeografia de los anofelinos en Venezuela: I. Los doe vectores principales. Tijeret. sobre Malar. 10:19-32, 1946.
¹⁰⁷ Gabaldon, A., and Cova-Garciá, P.: Zoogeografia de los anofelinos en Venezuela: II. Los vectores secundarious y los no vectores. Tijeret. sobre Malar. 10: 78-127, 1946.
¹⁰⁸ Gabaldon, A., and Cova-Garciá, P.: Zoogeograff a de los anofelinos en Venezuela: III Relaciones con el Terreno y Clima. Tijeret. sobre Malar. 10 : 164-179, 1946.
¹⁰⁹ Berti, A. L., and Montesinos, M.: Cultivos de arroz en relación con la malaria: el problesma en Venezuela. Cuad. verde Com. ejecut, 3a Conf. interamer. Agricultura No. 52, pp.1-33, Caraças, 1946.

from the Division of Malariology. Such permits required proper leveling of the land and specified that each 4 days of flooding be followed by 4 days of draining and that larvicides must also be used. Permits were not issued for land that could not be dried out in 4 days.

    British Guiana (Demerara). - This colony extends about 500 miles from north to south with an average width of perhaps 200 miles. The population is comparatively small and is found in the rather narrow coastal plain, which is very fertile. That portion which is below high tide is protected by seawalls. Sugarcane and rice culture prevail. The intermediate zone, which extends southward, produces diamonds, gold, and bauxite. Great masses of highland lie in the western and southern parts. There are many waterfalls.

    A very high relative humidity renders the jungle areas oppressive, but a sea breeze makes the vicinity of Georgetown more tolerable.

    The coastal population is a mixture of Negroes, Chinese, Portuguese, and East Indians.

    Malaria in British Guiana has always been severe.¹¹⁰ Deaths from malaria in 1946 stood at approximately 2 per 1,000 per annum. The disease ranked second as a reported cause of death in 1939, following pneumonia; but, if undefined fevers are taken into account, it probably deserved first place. In 1941, it was so reported. All forms of the Plasmodium are present. Blackwater fever occurred more frequently than in any other Atlantic base used by the Armed Forces.

    Anopheles darlingi, A. albitarsis, and A. aquasalis are all involved, with A. darlingi the leading vector.

    The control problem is complicated because there are two dry seasons and two wet seasons, with not much time between for a definite malaria program. British reports for 1941 speak of malaria being "greatly decreased" because of abnormal and prolonged drought. Nevertheless, government agencies hospitalized 1,356 cases (77 deaths), and 4,359 outpatient cases were handled. In the Colony as a whole, 288 deaths were registered as due to malaria in 1941.¹¹¹

    The site selected for the U.S. military base was a sandy elevation, 22 miles south of the city of Georgetown on the east bank of the Demerara River between the mouths of two tributaries, the Madewini River and the Hauraruni River. It was necessary to remove a rambling, native village (Hyde Park), which lay on low ground along the Demerara, and resettle the inhabitants outside the area. It became the policy to keep native habitations away from the windward side of camp. ¹¹²

¹¹⁰ Stage, H. H., and Giglioli, G.: Observations on Mosquito and Malaria Control in the Caribbean Area. Part II. British Guiana. Mosquito News 7: 73-76, 1947.
¹¹¹ Medical and Sanitary Reports from British Colonies, Protectorates and Dependencies for the Years 1939-1941. British Guiana, 1941. Trop. Dis. Bull. 43 (Suppl.): 215-217, 1946.
¹¹² Medical and Sanitary Data on British Guiana. Compiled by the Medical Intelligence Branch, Preventive Medicine Division. Office of The Surgeon General, U.S. Army, 19 Sept. 1942.

    The expected vector, A. darlingi, was not recorded about the site of the U.S. base in 1941, but A. aquasalis was. This species bred in the tidal swamps along the Demerara River. Such swamps were present all along the waterfront, and breeding also took place in borrow pits, along the road. However, a drainage and filling program was launched to eliminate breeding places, and only about 20 cases of malaria occurred among construction forces during the first 9 months of operation. There was one death, in July 1941.

    At the labor camp at Hyde Park, an attempt was made to segregate chronic malaria carriers from nonimmunes. At first, these were housed three-quarters of a mile from the construction camp. Later, they were moved to the boundaries of the base.

    Throughout the next 3 years, malaria control work was continued, with emphasis on maintenance of established ditches and oiling of various swamps. In December 1944, at the request of the surgeon of the Caribbean Defense Command, the 392d Medical Composite Unit of Trinidad made mosquito and parasite surveys with reference to the detection of both malaria and filariasis.

    The incidence of malaria at Atkinson Field never reached higher than 30 per 1,000 per annum for any month of 1944, and during the last quarter, no case of primary malaria was reported. The majority of all 1944 cases were contracted off the base.

    Surinam (Dutch Guiana). - The low coastal belt is patterned with tortuous rivers, influenced by tides. South of this is a triangular area of savanna country, with the broad base lying west. Still further south are highlands, with mountain peaks rising to above 3,000 feet.

    Four seasons are recognized: The long rainy season from April through July; the long dry season from August through November; the short rainy season covering December and January; and the short dry season during February and March.

    U.S. military interest was much concerned with the production and transportation of aluminum. The mines at Moengo and Paranam, the airport at Zanderij, and the port city, Paramaribo, which is also the capital, represented areas in which health problems might be important.

    Colonel Fox considered health conditions better in Surinam than in French or British Guiana, due, in his opinion, to more effective administration.¹¹³ Population pattern is scarcely an explanation, as Surinam has all the racial elements of the other colonies in addition to many Javanese, who constitute over 20 percent of the whole. The climate is no more salutary.

    Malaria is endemic throughout Surinam, though not uniformly. In general, the malaria curve follows the rainfall curve.

    Morbidity charts show a decided peak after the beginning of the long rainy season (May 15 to August 15) and a lesser peak about the end of the

¹¹³ Report, Lt. Col. Leon A. Fox, MC, U.S. Army, subject: Sanitary Survey of Dutch Guiana (Surinam). 6-14 Sept. 1941.

short wet season November 15 to February 15. Cyclic outbreaks of epidemic proportions also occur.

    Wolff ¹¹⁴ considers that the movements of populations seeking employment during the years of economic crisis (1932 and 1933) served to distribute malaria more widely in Surinam.

    In some areas, infection is perhaps universal, with a partial immunity tolerance. Disease, under such conditions, may be thought of as a "lapse from immunity." General Fox, in palpating the abdomens of 47 children estimated to be in the age group "6 months to 3 years" found only one enlarged spleen, but this is certainly not typical, since Wolff reports spleen rates among tribal populations as ranging from 20 to 100 percent. The carrier rate among bush Negroes is believed to be 100 percent.

    Wolff discriminates between the coastal region, in which malaria is moderately endemic, and the interior, where the endemicity is high. In the interior, the estivo-autumnal type predominates.

    The anopheline fauna of Surinam is rich in species. According to van der Kuyp,¹¹⁵ collections made in 1946 included A. darlingi Root, Anopheles darlingi var. paulistensis Galvâo, Lane and Correa, A. aquasalis Curry, Anopheles oswaldoi Peryassú Anopheles triannulatus davisi Paterson and Shannon, and A. nuñez-tovari present in Surinam. (The variety A. darlingi paulistensis is not considered distinct by all entomologists.) Anopheles aquasalis, A. bellator, A. darlingi, and A. albitarsis are among the potential vectors, with A. darlingi most dangerous in the interior, and A. aquasalis the principal offender on the coast.

    Before the war, mosquito control measures were limited, though the companies operating the bauxite mines made serious effort in the immediate vicinity of their activities. ¹¹⁶

    French Guiana . - As in Surinam, malaria is widespread.¹¹⁷ It is especially common in the penal colonies and mining camps. East Indians are frequent sufferers, but the bush Negroes enjoy relative immunity and are rather refractory to clinical attacks. In 1935, blood smears examined at the Institute of Public Health in Cayenne showed 72 percent P. falciparum, 20 percent P. vivax, 6 percent P. malariae, and 2 percent mixed infections.

    According to Floch, ¹¹⁸ P. falciparum malaria is now everywhere more prevalent than P. vivax. This is in marked contrast to the findings of Marcel

¹¹⁴ Wolff, A. E.: Malaria in Surinam. Bol. Ofic. san. panam. 25: 335-338, April 1946.
¹¹⁵ Van der Kuyp, E.: Preliminary Report on the Subgenus Nyssorhynchus (Diptera, Culicidae) of Surinam (Dutch Guiana). Docum. neerl. et indones. de morbis trop. 1:67-68, 1949.
¹¹⁶ Medical and Sanitary Data on Surinam. Prepared by the Medical Intelligence Branch, Preventive Medicine Division, Office of The Surgeon General; U.S. Army, 27 May 1943.
¹¹⁷ Medical and Sanitary Data on French Guiana. Compiled by the Medical Intelligence Branch, Preventive Medicine Division, Office of The Surgeon General, U.S. Army, 29 May 1943;
¹¹⁸ Floch, H.: L'endémo-epidémic palustre en Guyane francaise. Institut Pasteur de la Guyane et du Territoire de l' Inini. Publ. No. 165, October 1947. Abstr: Trop. Dis. Bull. 45: 749-750, September 1948.

Léger ¹¹⁹ in 1917, when 68 percent of all infections were reported to be due to P. vivax and only 28 percent to P. falciparum. Present figures, representing blood examinations over an 8-year period, give P. falciparum 81 percent, P. vivax 17 percent, and P. malariae 1.5 percent. Either Léger's data were not representative or the various population movements of subsequent years have substantially altered the endemic reservoir. Epidemic manifestations, it should be pointed out, occur in the dry season.

    Of the principal vectors, according to Floch, A. darlingi constitutes 91 percent of the mosquitoes taken in houses, while A. aquasalis makes up 46 percent of those captured outside. Anopheles darlingi is a fresh water breeder, while A. aquasalis is found in brackish situations.

    In 1943, the city of Cayenne was reported to be fairly free of anophelines, partly because of drainage projects but also because of favorable winds.

Development of Control in the Antilles Department

General information

    For the Antilles Department as a whole, malaria was at first one of the greatest causes of noneffectiveness. By 1945, it ranked among less important categories. ¹²⁰ This was due, of course, to continuous and close attention to all aspects of the control program. At any time, all gains could easily have been erased if preventive measures had been relaxed. Throughout the war, in the same overall area, morbidity and mortality rates in civilian populations continued high.

    Civilian reports for the year 1941 show that malaria was a problem in various Caribbean locations. In Dominica, 4,579 cases were reported, with 58 deaths.¹²¹ In Saint Vincent, malaria accounted for 550 cases, with 2 deaths. ¹²² In Turks and Caicos Islands, there was an epidemic.¹²³ In Montserrat, malaria was on the increase, and a serious outbreak occurred in the windward area near the Farm River. Thirty deaths from malaria occurred in the Island that year.¹²⁴ Malaria was mild in the Virgin Islands (Great Britain) with only 9 inpatients and 413 outpatients reported ^.125 The previous year Grenada had suffered an epidemic, with 10,383 cases and 97 deaths, in eight districts.¹²⁶

¹¹⁹ Léger, M.: Le paludisme a la Guyane Française: Index endémique de diverses localités. Bull.Soc. path. exot. 10: 749, 1917.
¹²⁰ See footnote 89, p. 202.
¹²¹ Medical and Sanitary Reports from British Colonies, Protectorates and Dependencies for the years 1939-1941. Dominica, 1941. Trop. Dis. Bull. 43 (Suppl.): 238-239, 1946.
¹²² Medical and Sanitary Reports from British Colonies, Protectorates and Dependencies for the years 1939-1941. St. Vincent 1941. Trop. Dis. Bull. 43 (Suppl.): 257-258, 1946.
¹²³ Medical and Sanitary Reports from British Colonies, Protectorates and Dependencies for the years 1939-1941. Turks and Caicos islands, 1941. Trop. Dis. Bull. 43 (Suppl.) : 230-231, 1946.
¹²⁴ Medical and Sanitary Reports from British Colonies, Protectorates and Dependencies for the years 1939-1941. Montserrat, 1941. Trop. Dis. Bull. 43 (Suppl.): 242-243, 1946.
¹²⁵ Medical and Sanitary Reports from British Colonies, Protectorates and Dependencies for the years 1939-1941. Virgin Islands, 1941. Trop, Dis. Bull. 43 (Suppl.): 246-247, 1946.
¹²⁶ Medical and Sanitary Reports from British Colonies, Protectorates and Dependencies for the years 1939-1941. Grenada, 1940. Trop. Dis. Bull. 43 (Suppl.): 249-251, 1946.

    In Trinidad and Tobago, malaria continued to occupy first place among diseases responsible for civilian ill health and disability.¹²⁷ The number of cases actually reported in 1941 was 15,385, but as the disease was not notifiable, this was only an indication of the much greater number of people who presumably were ill. Deaths for that year numbered 484 as compared with 431 in the previous year.

    Reports for 1942 were encouraging or ominous, according to locality. For the Puerto Rican Sector, general health was considered good except for high venereal and malarial rates. The latter incided at the rate of 73 per 1,000 Army personnel per annum in April 1942. This represented a marked increase over that of the same month of the previous year. This was believed due to unseasonal rains, to increase in the number of native troops, many of whom were already infected, and to increased dispersion of troops. Although mosquito netting was available in satisfactory amounts, wire screening was scarce. Troops not on posts were given quinine as a prophylactic measure. This is of interest, since quinine soon became too scarce for even therapeutic use, except in special cases.

    Only two military cases of malaria were reported in May 1942 from Antigua, though civilian malarial rates were high. No drug prophylaxis was used there.

    Malaria was reported as unknown in Aruba with but. few cases in Curaçao, all contracted before arrival.

    High malarial rates, as expected, were reported from Trinidad, where sleeping under nets was made mandatory. Troops on jungle duty, away from posts, were given malaria prophylaxis. Antimalaria sanitation in Trinidad was the responsibility of the district engineer.

    Before September 1943 and to some extent thereafter, mosquito control was handicapped by lack of a regular supply of insect sprays and larvicidal oil. All installations were screened, and the screening inspected and repaired weekly. Temporary repairs with netting, cloth, rags, or lumber were frequently necessary until replacement screening became available. Bed nets were issued, and periodic inspection employed to insure proper use and repair. Most of the cases of malaria, occurred among personnel serving as night guards. Although head nets and gloves were issued, enforcement of their use proved difficult or impossible. At this time, repellents were not available.

    Up to the year 1943, conditions in Puerto Rico gave the Antilles Department considerable concern. The background was not encouraging. The disease was known to kill approximately 2,000 inhabitants on the average per year. The Insular Health Department records for 1940 showed 23,758 cases in 1940 with 1,817 deaths. For 1941, the figures were 23,484 cases and 2,282 deaths. This represented rates of 1,228.7 and 124.6 per 100,000. For 1942, the rates were 1,099.8 and 99.4, respectively.

¹²⁷ Medical and Sanitary Reports from British Colonies, Protectorates and Dependencies for the years 1939-1941. Trinidad and Tobago 1941. Trop. Dis. Bull. 43 (Suppl.) 263-266, 1946.

    Malaria ranked as one of the chief causes of disability among Armed Forces in the island in 1942, but as a minor cause in 1943, a tribute to the fidelity with which the military authorities had applied whatever control measures were available.

    The Insular Health Department, of course, did its share, but with limited funds. In their program, emphasis was placed largely on treatment of patients to reduce mortality and to eliminate foci of infection.

    An important phase of the Army's control program was the continual survey of anopheline densities. Gratifying reductions were noted as a result of both temporary and permanent control measures at (and near) Camp O'Reilly, Fort Buchanan, P.R., Camp Tortuguero, and Losey Field. Studies of anopheline breeding areas and field surveys to obtain epidemiological data were carried out during 1943 at three other installations on Puerto Rico also at Benedict Field, Saint Croix, and Fort Simonds.

    A new type of malaria report card was introduced in January 1943, greatly facilitating the assembling and analysis of data. Classification. of primary and recurrent cases was made relatively easy, in accordance with the following pattern:
    1. Camp. Individuals who did not leave their home station during the 30 days before illness.
    2. Camp and pass. Individuals who were out of camp on overnight pass from 8 to 30 days before illness.
    3. Camp and different night station. Individuals who left camp to assume duty at a different station during night hours.
    4. Maneuvers. Individuals who participated in field maneuvers from 8 to 30 days before illness.
    5. Civilian life. Individuals who entered the Army 8 to 30 days before illness.

    Cases of vivax malaria were considered relapses if there was a history of previous malaria within 12 months. With falciparum malaria, 6 months was the limit used.

    If a change of station occurred within 7 days before the onset of illness, the case was considered as of the old station. When changes occurred from 8 to 30 days before onset, the case was attributed to the station where the greater portion of the time had been spent.

    Such a careful analysis made it possible to be much fairer in evaluating the effectiveness of antimalaria programs at various posts. For example, in earlier reports, many cases were attributed to Henry Barracks, simply because they were diagnosed there. Of the 34 cases hospitalized at Henry Barracks during the first 6 months of 1943, 32 proved to have been contracted off the post. This was in harmony with anopheline catches, which had been low for some time,

    Sanitary Corps officers were generally assigned as post malaria control officers. Where extensive control projects were undertaken, two Medical

Department enlisted men with special qualifications were assigned to each station hospital for malaria control duty. Antimalaria housekeeping measures were their chief responsibility.

    During November and December 1943, data on mosquito densities and mosquitoproofing standards were systematically collected at many posts. To determine the "intra-cantonment adult mosquito index," mosquitoes were collected each week from a representative number of occupied buildings and classified as to anopheline and nonanopheline. To determine the "mosquitoproofing index," a representative number of buildings were visited, and defects were recorded. This stimulated both interest and action. In many cases, a reduction of the mosquito index to zero was attained.

    The year 1944 was fortunate from the malaria standpoint.¹²⁸ The incidence of the disease was low, not only among Army personnel, but also among natives in unsanitated areas. The dry season, combined with a natural, cyclical low point for the region, supplemented the effects of a well-developed anti-malaria program.

    In the Puerto Rican Sector, the attack rate for January 1944 was 13 as compared with 63 for January 1943 and 142 for January 1942. For February 1944, the ratio was 6:48:104; for March 6:25:99; and for April 4:7:73.

    Improvement in the Trinidad Sector was less striking, but in general parallel; the attack rate for January 1944 was 53.6 as compared with 51 for January 1943 and 69 for January 1942. For February 1944, the ratio was 22: 53.1: 57; for March 27: 66: 74; for April 20: 35: 49. It should be pointed out, of course, that in Trinidad the peak of the malaria season occurs in late summer. Thus, the attack rate in August for 1942 was roughly 105 per 1,000 per annum. In August 1943, this had been reduced to approximately 66. In the Panama Canal Department, the attack rate for January 1944 was 22.6; for February, 19.4; for March, 8.3; for April, 6.2. These figures include both primary and recurrent malaria (table 24).

    By 1945, the problem became one of maintaining the preventive measures which had brought about the gratifyingly low rate then prevailing among military personnel. High morbidity and mortality rates were still characteristic of civilian populations in the Antilles Department.

    Costs were decreasing, as emphasis was then on maintenance of drainage ditches rather than on their construction.

    The larvicide principally used was an emulsion composed of 3 parts water to 1 part diesel or fuel oil, with DDT added to the oil ingredient.

    Both larviciding and spray killing of adults were then being handled by plane, the large capacity C-47 being found most practical. Much hand larviciding could thus be eliminated, and hitherto impenetrable areas covered. Residual effects lasted up to 6 weeks.

    Spraying of barracks and civilian homes with DDT at bimonthly intervals had become established practice.

¹²⁸ Essential Technical Medical Data, Caribbean Defense Command, April 1944.

    Individual control measures assumed renewed importance on posts where strengths were being cut, and environmental control measures were becoming no longer feasible from an economic standpoint. A continuing educational program was therefore necessary.

Administration

    On 4 December 1942, a Department malaria control officer was appointed by the commanding general to function under the Department surgeon. His duties were to coordinate all malaria control activities at Army posts and to collaborate with agencies in charge of extracantonment malaria control programs. This officer traveled extensively, inspecting projects and advising post engineers, post surgeons, and commanding officers.

    The advisory function was broadened before the end of the year by the establishment of a Department malaria control board, consisting of the Department malaria control officer, a representative of the U.S. Public Health Service, and a representative of the District Engineers Office. Post commanders made full use of the services of this board and thus insured that their plans and projects were in accord with the best malaria control principles.

    The U.S. Public Health Service, of course, did not operate extracantonment projects in connection with every post. For other posts, it was arranged that the District engineer should be responsible in carrying out extracantonment projects formulated by the respective post commanders. The advice and assistance of the Department malaria control board was available at all times. Thus, each post was assured the proper combination of intracantonment and extracantonment control work to meet its particular needs.

    Medical Department officers who held the title of "Malaria Control Officer" in the Office of the Surgeon, Antilles Department., included:

    Maj. Louis Gonzalez, MC, 15 December 1943 to 26 May 1944.
    Capt. Rafael Rodriguez-Molina, MC, 26 May 1944 to 23 June 1944.
    Maj. Leonard B. Dworsky, SnC, 23 June 1944 to 1 November 1944.
    Capt. Francis B. Frost, SnC, 1 November 1944 to 18 January 1945.

Puerto Rican Sector

    Although the division of the Antilles Department into two Sectors was not continued to the end of the war, it will be convenient to present the essential material in this manner.

    In 1943, the Puerto Rican Sector included 12 stations. The eight Ground Force stations were:
        Post of San Juan, including station hospital, P.R.
        Camp O'Reilly, P.R
        Fort Buchanan, P.R.
        Henry Barracks, P.R.
        Camp Tortuguero, P.R.

    Saint Thomas, V.I.
    Antigua, B.W.I.
    Jamaica, B.W.I.

The Air Force stations were four:
    Borinquen Field, P.R.
    Losey Field, P.R.
    Benedict Field, St. Croix, V.1.
    San Julián, Cuba.

    The Air Force station at San Julián, Cuba, was added after the 1942 report, representing an increase of five stations over 1941.

MALARIA PROBLEMS, 1941-43

    The malaria situation in the Puerto Rican Department, at the beginning of the war, is summarized in table 28.

TABLE 28 . - Malaria data for U.S. Army enlisted personnel in Puerto Rico, continental troops, and insular troops, 1941

    During the first 30 weeks of 1942, the malaria attack rate of troops in Puerto Rico had reached 114 per 1,000 strength. For the first 21 weeks of the same year, the figure stood at 74.2 per 1,000 strength in Panama. The rate of primary malaria in the PCD for the 4 weeks ending 26 June 1942 was 233.1 per 1,000, ¹²⁹ in spite of the fact that the Caribbean Defense Command had been utilizing all the malaria control measures thus far developed for use by troops. It became essential that The Surgeon General should have firsthand information regarding malaria problems and control methods in these areas.

    It was therefore arranged that Lt. Col. (later Col.) Paul F. Russell, MC, in company with Dr. Mark F. Boyd, of the Rockefeller Foundation, both experienced malariologists, should proceed to San Juan, during September 1942, and make a similar journey to the PCD, in October 1942, for the purpose of obtaining the desired information.

¹²⁹ Letter, Col. John A. Rogers, MC, Executive Officer, Office of The Surgeon General, to The Commanding General, Services of Supply, 31 Aug. 1942, subject: Malaria Control.

    The Puerto Rican survey disclosed that some cantonments had achieved rates of 250 per 1,000 strength during 1941 and 1942.¹³⁰ Good cooperative relations existed between the Army, the U.S. Public Health Service, the Insular Health Department, and the Work Projects Administration, but specific plans for intracantonment and extracantonment control for each installation were yet to be developed. The Insular Health Department had made no sustained effort to deal with the menace of the civilian reservoir living outside cantonments, and the Army had been slow in assuming its full responsibility for intracantonment control. Some of this had been compensated for by the activity of the U.S. Public Health Service, which lent considerable aid of an emergency nature, but it had been understood from the beginning that the prime responsibility of the U.S. Public Health Service was extracantonment control and that the Army was expected to look after intracantonment control in all its phases.

    The Russell-Boyd report resulted in specific recommendations to the effect that the Army assume full responsibility for intracantonment control, including larviciding and drainage. The antimalaria program of the Army in Puerto Rico had up to this time been limited to screening, minor ditching and oiling, pit-filling projects, and the use of bed nets, protective clothing, and suppressive drugs. Some survey work had been in operation since 1 June 1942. The recommendations advocated greater use of pyrethrum sprays to kill adult mosquitoes, also that bed nets be included in the screening inspection.

    Most significant was the suggestion that a full-time malaria control officer, with suitable assistants, be appointed for the Puerto Rican Department and that he be placed on the staff of the Department surgeon. Considerable time was to elapse before this was achieved.

    The sanitation of the entire Puerto Rican Sector in 1942 was reported good, "except for the presence of malaria vectors throughout the year, especially at Fort Buchanan, Losey Field, and Camp Tortuguero." The same memorandum states that the development of auxiliary airdromes along the coastal plain of the island of Puerto Rico had appreciably increased the seriousness of the malaria problem.

    Most of the U.S. military posts in Puerto Rico were located on the coastal plain, where malaria is endemic. Fort Buchanan, Losey Field, and Camp Tortuguero presented the greatest problems. In hyperendemic areas nearby, the spleen rate in children between 2 and 10 years was permanently over 50 percent.

    In the Salinas area, which was used for military maneuvers, the annual attack rate among some 10,500 men was between 200 and 300 per 1,000 in 1941.

    The temperature in Puerto Rico varies from 72 ⁰ to 86 ⁰ F., so that mosquito production never ceases because of cold. Seasonal temperatures do affect

¹³⁰ Letter, Col. John A. Rogers, MC, Executive Officer, [Office of the Surgeon General, U.S. Army], to The Adjutant General, [War Department], 23 Oct. 1942, subject: The control of Malaria in Puerto Rico.

mosquito production, nevertheless, as shown by the fact that adult emergence usually drops sharply in mid-December and continues relatively low for 2 or 3 months, the rate of larval development being reduced about 50 percent. Malarial infections tend to fall off 4 to 6 weeks after adult emergence is checked.

    More important than temperature, of course, are the seasonal variations in rainfall. Increase in precipitation is reflected in higher mosquito counts and more malaria. A third factor in A. albimanus production is shade. When the sugarcane becomes sufficiently tall, A. albimanus tends to be replaced by A. grabhami.

    Surveys carried out among civilian populations revealed a parasite rate between 20 and 40 percent, especially along the southern coast. Some 2,000 deaths due to malaria were reported annually. With limited funds, the Insular Health Departments program consisted of (1) treating patients to reduce mortality and eliminate foci of infection, (2) antilarval work in a number of hyperendemic districts, and (3) permanent engineering projects in selected districts where the problem was most severe.

    Military reports for 1941 and 1942 in Puerto Rico show annual incidence rates among enlisted personnel of 84 and 86 per 1,000, respectively. The latter portion of 1942 showed marked improvement, however, particularly at Fort Buchanan, where a rate of 45 per 1,000 prevailed in October, November, and December as compared with 213, 137, and 273 for the corresponding 3 months of 1941, 1940, and 1939.

    This degree of success in controlling malaria at Fort Buchanan was attributed chiefly to screening, insecticiding, and malaria discipline since the anopheline density had been reduced appreciably only in central areas of the somewhat sprawling post. Viewed in retrospect, it seems probable that larviciding and drainage also helped, but such opinion was not held at the time by those responsible for current reports.

    Even after the numbers taken in bait traps had become considerably lower, the malaria hazard remained great; however, a reduction in the number of malaria carriers was effected by the evacuation of the small village of Colonia Santa Ana. At the same time, many old troops were transferred, thus eliminating a goodly portion of the human reservoir. Increased efforts were also put forward to detect the carriers among new inductees and to prevent these cases from becoming centers of infection among the troops.

    At Losey Field, Fort Buchanan, and Camp Tortuguero, wastelands and pasturelands contributed extensively to anopheline breeding, and wet fields of sugarcane were also important in certain instances. Irrigation channels and reservoirs, streams and cutover mangrove swamps characterized the vicinity of Losey Field. At Fort Buchanan, the worst breeding areas were manmade, in that hydraulic fill had blocked certain natural drainage outlets, creating scattered bodies of shallow, impounded water. At Camp Tortuguero, large areas of waste marshland, formerly in cane, produced many anophelines. The marshy fringes of Laguna Tortuguero were next in importance. At

Camp O'Reilly, old sugarcane ditches, in addition to at least four small streams. were sources of breeding.

PROBLEMS AT SELECTED POSTS

    Camp Tortuguero . - As stated previously, this post was surrounded by extensive sugarcane fields and large bodies of standing water. Within the camp boundaries were Laguna Rica, Laguna Tortuguero, and a seepage area at the base of a hill. Five hundred acres or more of marshland lay to the east of the camp, and there were several nearby "barrios," practically surrounded by canefields. The nearby towns of Vega Baja, P.R., and Manatí, also malarious, were frequently visited by troops.

    Within the camp, malaria control was accomplished by oiling all breeding places or dusting with paris green. Ditching, drainage, and filling were also employed. All buildings used at night were screened. The use of mosquito bar and of Freon Aerosol was made compulsory. Routine inspections, also group instruction and demonstrations were employed. Informative posters concerning individual precautions were placed in hutments. Weekly catches of mosquitoes were made in occupied hutments to test the efficiency of the program.

    Camp O'Reilly . - War Department Training Circular No. 108, dated 21 September 1943, had its influence in the Caribbean as elsewhere. A report from Camp O'Reilly mentions the appointment of antimalaria details by all organizations and their training by the post malaria control officer. Barracks were regularly inspected and scored as to the defects found. These reports were sent to post headquarters, and each organization was notified by the post commander as to the defects recorded.

    The prevalence of mosquitoes at Camp O'Reilly was likewise reduced by both intracantonment and extracantonment drainage and by extensive larviciding. The malaria rate for 1942 was only 113 per 1,000 average strength per year, and for 60 percent of the months of 1943, less than 20 per 1,000 strength. The construction of permanent linings in ditches and watercourses upon the post was a feature of the control activities.

    An important step in the sanitation of Camp O'Reilly was the relieving of one Sanitary Corps officer, in 1943, of the duty of mess inspection and the utilization of this officer, as post malaria control officer, to work in cooperation with the post engineer.

    The 1944 Annual Report, Department Surgeon, Antilles Department, compares the malaria rate for 1942, which was 113 per 1,000 per annum, with 30 per 1,000 per annum for 1943 and 6 per 1,000 per annum for 1944.

    This was accomplished entirely before the availability of DDT and resulted from conscientious attention to many things. Particularly influential was an exhibit, opened in April 1944, at the 326th Station Hospital, which all enlisted men of the command were required to visit in groups of ten.

Explained and demonstrated were the use of the mosquito bar, how to tuck it well under the mattress, how to repair holes by mending or patching; likewise the use of head nets, gloves, leggings, and repellent. The use of Panama inverts, and side slabs, and the sodding of banks with Bermuda grass were pictured, also dusting, oiling, and cleaning of ditches. The work of both military and U.S. Public Health personnel, within and without the cantonment, was likewise shown.

    Losey Field . - The largest and most uncontrollable breeding areas at Losey Field and Camp Tortuguero were eventually reduced or eliminated by drainage construction, carried out by the U.S. Public Health Service and the Work Projects Administration, ¹³¹ chiefly in 1943. Previous to this, Losey Field had posed a difficult problem. The area, covering about 240 acres, was purchased by local donations and given to the government. Useless for agriculture, because of its swampy nature, the land is only 20 feet above sea level. The distance to the sea is about 1¹/2 miles. Cost of drainage could not be other than excessive. The Insular Health Department spent approximately $70,000 in malaria control in the Losey Field area in 1941, which included 92,707 lineal feet of pipe in subtile drainage, and $800 per month for oiling and spraying.

    Borinquen Field, P.R - At this base, malaria control was at first confined largely to the use of screens and mosquito bars. The malaria rate rose, until, in July 1942,  it had reached 100 per 1,000 per annum (as compared with 62 for July 1941).

    Vigorous measures were instituted, including a program of filling, draining, and oiling. Bajura Pond, a sea-level swamp at the northeast corner of the base, very difficult to drain, was eventually taken care of by dusting once a week from the air with a mixture of alum (or lime) and paris green.

    The malaria rate for July 1943 was only 6 per 1,000 per annum. For the balance of the year, only 9 cases were reported, and most of these were among coastguardsmen quartered off the post or in soldiers who had been on pass in malarious territory.

MISCELLANEOUS REPORTS FOR 1944

    Reports for 1944 (in some cases referring to work accomplished in 1943) showed that the situation was well in hand.

    At Fort Bundy, where DDT began to be used in October 1944, the number of malaria-transmitting mosquitoes taken in surveys ranged from one-fourth to one-tenth the number found in previous months, as, for example, 739 collected in November 1944 versus 9,235 collected in September 1944.

    At Losey Field, 15 cases of malaria were contracted among troops undergoing training in the Salinas Training Area; but these were proved to be the result of relaxed malaria discipline, and corrective measures were immediately

¹³¹ Letter, John M. Henderson, Sanitary Engineer, (R) Federal Security Agency, U. S. Public Health Service, San Juan, P.R., to Lt. Col. Paul F. Russell, MC, Office of The Surgeon General, 19 July 1943, subject: Civilian and Army Malaria Morbidity by Months in Puerto Rico.

instituted. Suppressive Atabrine therapy was also authorized for troops in the Salinas Training Area.

    At Fort Buchanan, the malaria problem was practically eliminated by a combination of all available procedures and by cooperation between U.S. Engineer Department, post engineer, U.S. Public Health Service, Work Projects Administration, and other agencies. Drainage, larviciding, attention to barracks, and malaria discipline, all had a part. Post malaria control officers (Sanitary Corps) discharged the following duties:
    1. Supervision of post engineer larviciding and minor ditching crew. (This function was somewhat nominal. On most posts, including Fort Buchanan, such crews worked directly under the authority of the post engineer.)
    2. Supervision of four malaria control technicians who were concerned both with the control programs of the post and of the Antilles General Depot areas.
    3. The collection, tabulation, and review of data relating to mosquito control.
    4. The review of data secured from malaria patients.
    5. Supervision of and participation in the malaria control education program for troops.
    6. Regular inspection of all intracantonment breeding areas and the recommendation of corrective measures.
    7. The inspection of sleeping quarters of troops.
    8. The preparation of all required reports on malaria control.

    At Camp Tortuguero, conscientious attention to all aspects of the problem continued to create a better record. Chief difficulty at this post was the condition of quarters for troops, where separation of boards due to excessive rainfall and changeable weather caused many cracks capable of admitting mosquitoes. The post engineer kept a permanent repair crew employed at mosquitoproofing work.

    Results of the use of DDT larvicidal dust, also of 5 percent DDT in No. 2 diesel oil, were beginning to be observed.

    At Henry Barracks, the malaria problem was reported as "minimal" in 1944. About three-fourths of the area of the post had been improved that year with 1,500 linear feet of half round acres (estimate) drained, but this is not considered to have had a real bearing on malaria, as Henry Barracks enjoyed a very good record from 1941 on.

CONCLUDING STATEMENT

    The decrease of malaria in the Puerto Rican area during the course of the war may be illustrated by the statistics in table 29, from the 161st General Hospital, Fort Brooke. ¹³² No cerebral malaria was recorded at this hospital.

¹³² Professional History of Internal Medicine in World War II, the Antilles Department. [Official record.]

    The prompt establishment of adequate antimalaria control measures, including the institution of malaria discipline, was believed to be the factor influencing the rapid decrease in the incidence of malaria among Army personnel.

    Adequate malaria control was not accomplished until sometime in 1943, after which a rapid decrease in malaria incidence took place. Through most of 1942, malaria rates in Puerto Rico remained undesirably high. Colonel Russell, who visited the island during 1942, recorded conditions as "distressingly bad." Even minor repairs of barracks, necessary for mosquitoproofing were not given proper attention on many posts until the last 6 months of 1943.

TABLE 29. - Admissions for malaria, 161st General Hospital, San Juan, P.R., 1942-45

    The role played by the Malaria Control in War Areas, US. Public. Health Service, in Puerto Rico, especially during the critical 1942-43 period, was very great. For a number of reasons, the Army did not achieve proper organization for adequate malaria control until sometime in 1943, and preventive medicine units did not actually take the field to any extent until 1944. Tardy recognition of these organizational needs not infrequently resulted in the assignment of unsuitable personnel for control work, and lack of proper planning in the selection of campsites can probably be traced to the same source. Meantime, MCWA, with its self-contained units or "teams" was chiefly responsible for the functioning of the joint Army malaria control program as it was then constituted.

Trinidad Sector ¹³³

CONSTRUCTION PERIOD

    The first and foremost problem confronting the U.S. military authorities in the Caribbean was the construction of bases to receive large numbers of U.S. troops. This task fell to the Corps of Engineers and was administered by Districts.

    Of these, the Trinidad District was perhaps the most important from the malaria hazard standpoint. Toward the end of December 1940, Lt. Col. (later

¹³³ Data on civilian malaria and its vectors have been included in the previous section on countries and dependencies.

Lt. Gen.) David A. D. Ogden arrived in Port of Spain as district engineer, accompanied by 2 officers of the Corps of Engineers and 36 civilian employees. This group supervised the construction of the various bases involved. Much native labor was employed. Port of Spain served as headquarters for all work in time Trinidad District.

    Three areas were recognized, the British Guiana Area, which contained Atkinson Field, the Saint Lucia Area, which contained Beane Field, and the central or Trinidad Area, administered from Fort Read. Included under the Trinidad Area were Fort Read, Waller Field, a number of auxiliary airfields, certain fixed defense units of the. Caribbean Defense Command, and the permanent docks.

    The Trinidad Area gave greatest concern, as two endemic centers were involved. One of these centers consisted of the coastal swamps, which were breeding places for A. aquasalis. The other endemic center was in the highlands, where there is plenty of rainfall, and proved to be due to the abundance of A. bellator, a hitherto suspected but not proved vector. As mentioned previously, these mosquitoes are treetop breeders. Proof of the natural infection of A. bellator was brought forward by Dr. Lloyd E. Rozeboom ¹³⁴ and Mr. Raymond Laird. of The Johns Hopkins University who arrived in Trinidad in May 1941 and found the first naturally infected bellator in July 1941.¹³⁵ Their findings were later confirmed by Downs and Shannon ¹³⁶ of the Rockefeller Foundation, while engaged in making a malaria survey of the Island.

    During the first 9 months of operations, there were 48 cases of malaria in Trinidad among construction forces, with 1 death.¹³⁷

    Draining, filling, and anti-bellator measures were conspicuously effective in reducing anophelines as compared with culicines. In June 1941, the ratio between anophelines and culicines was 1: 1, in December 1: 9. This is probably not too significant, however, as A. oswaldoi, a nonvector, appears to have contributed substantially to the former count.

MALARIA IN MILITARY PERSONNEL, 1941-45

    At the 359th Station Hospital, Fort Read, previously designated as the 41st General Hospital, a total of 1,142 primary and recurrent cases were admitted.¹³⁸ These were classified as follows:

                                                                                                Number

Plasmodium vivax .....................................................................807
Plasmodium falciparum .............................................................308
Plasmodium malariae .................................................................   1
Mixed infections...........................................................................  12
Unclassified..................................................................................  14

¹³⁴ Dr. Rozeboom received the Bailey K. Ashford Medal of the American Society of Tropical Medicine in recognition of his work on Anopheles bellator.
¹³⁵ See footnote 102. p. 206.
¹³⁶ Downs, W. G., Gillette, H. P. S.. and Shannon, E. C.: A Malarial Survey of Trinidad and Tobago, British West Indies. J. Nat. Malaria Soc. Suppl. 2: 5-44, 1943.
¹³⁷ See footnote 96. p. 205.
¹³⁸ See footnote 89, p. 202.

    Four cases of cerebral malaria were recorded, all due to P. falciparum. One failed to recover, the only death from malaria in the Antilles Department.

    During 1942, there were approximately 1,150 cases of malaria in U.S. Army forces in the Trinidad Sector, but by 1943, mosquito control programs had begun to yield generally satisfactory results. However, in many locations, detailed information as to the species concerned, their habits, and ecological requirements was incomplete or lacking. In such cases, the attack on the problem had to be general, which usually meant some waste of funds, materials, and manpower. ¹³⁹

    The Trinidad Sector and Base Command had the benefit of a malaria control laboratory located not far from the sector surgeon's office.¹⁴⁰ Built in 1942, this laboratory served, directly or indirectly, the entire sector, which was over 1,000 miles long. Besides the Dutch Islands of Aruba and Curacao, this included Las Piedras and Puerto La Cruz on the mainland of Venezuela, the Venezuelan Island of Patos, British Guiana, the British Islands of Trinidad and Saint Lucia, also Surinam (Dutch Guiana), and Rochambeau Field in French Guiana.

    Throughout its history, the laboratory was directed by a commanding officer who, with one exception, was a medical officer malariologist. (In early 1945, this post was held by an engineer.) The parasitologist and the entomologist originally assigned to the laboratory remained with the organization until its deactivation. Until near the end of 1944, an engineer also served in close cooperation with the central staff.

    The functions of the laboratory were defined as follows:
    1. To identify specimens of larvae and adult mosquitoes from the various bases and submit reports.
    2. To examine blood smears of all malaria cases.
    3. To make field investigations of control procedures.
    4. To collect, assemble, and interpret data submitted by hospitals and field personnel.
    5. To disseminate newer technical information regarding control methods and procedures.
    6. To provide other technical assistance.

    A more complete account of the laboratory will be given in a later section entitled "Special Units, Organizations, and Projects."

    A rather complete study of the Trinidad Sector was carried out by General Stayer. The program which he outlined was put into effect and operated as follows:
    Local surgeons were made responsible for malaria control as well as sanitation for their own posts and camps. Each local surgeon outlined the projects

¹³⁹ Letter, Col. R. E. Shum, A.G.D., Adjutant General, Trinidad Sector and Base Command, to Commanding Officers, All Posts, Camps. Stations, and Bases (Ground and Air Forces), Trinidad Sector and Base Command, attention: Surgeons and Post Engineers, 26 Jan. 1943, subject: Mosquito Control.
¹⁴⁰ Annual Report, Surgeon, Trinidad Sector and Base Command, 1942.

FIGURE 27. - Gypsy moth sprayer in use against bromeliads.

he believed necessary for the control of malaria in his area and submitted plans to the engineers for estimates. Funds were provided by the district engineer, with the local post engineer completing the project under the technical supervision of the local surgeon.

    As indicated previously, the malaria control laboratory undertook to identify mosquitoes sent in by fieldmen and to give advice on species control. This service was somewhat hampered by the frequent removal of experienced personnel for service at other points. The loss of Lt. Wilbur G. Downs was particularly regretted by the Sector surgeon.

    The problem of A. bellator was considered worst at Fort Read, in the center of Trinidad. It was said that, even if the entire Fort Read area were covered with concrete, the malaria problem there would not be affected.

    This was an exaggeration, but the statement is significant. The possibility of felling the immortelle trees, hauling them away, and burning them to destroy the bromeliads was rejected because of expense. More practical was the training of crews to climb the trees and cut out the bromeliads. The eventual employment of pressure pumps to spray the bromeliads with copper sulphate, which is toxic to the epiphytes, had to await the arrival of suitable machinery from the United States. The U.S. Department of Agriculture was instrumental in arranging the shipment from Greenfield, Mass., of a Bean power sprayer, formerly used in combating gypsy moth depredations in New England (fig. 27).

    The type of malaria control employed at each location depended upon the nature of the particular base. Thus, within the Trinidad Sector, U.S. installations fell into three categories, according to probable permanence. Six

were 99-year leased bases. These were Fort Read, Edinburgh Air Base, Green Hill Cantonment, Port of Spain, British Guiana Base Command, and Saint Lucia Base Command.

    Bases held only for the duration of the war included five individual stations in Surinam, an airbase in French Guiana, and the two Dutch Islands, Aruba (Camp Savaneta) and Curacao (Camp Suffisant).

    Small outposts, of indefinite number and permanence, were scattered throughout the Trinidad Sector and though occupied by relatively few men constituted a distinct health problem of their own. Malaria discipline was chiefly counted on in these situations. A single exception was La Lune, Trinidad, where mosquito breeding was limited to a restricted area along one border of the camp. Clearing and larviciding measures were found to be economically feasible and greatly reduced the mosquito problem.

    At bases to be held only for the duration of the war, control measures depended on the anopheline fauna. On Aruba and Curacao, no malaria problem existed. During the construction of the airbase in French Guiana, drainage, larviciding, and spray killing of adult mosquitoes were employed to protect the construction crews, which entered the area late in April 1943. On recommendation of the Trinidad Base Command, native labor camps and Puerto Rican labor camps were moved to 1 mile from the U.S. camp. So far as can be ascertained, construction was suspended before completion of the work, the base was never activated, and only a very restricted malaria control program was ever in operation at the base.

    Of the five temporary stations in Surinam, only Zanderij Field saw an extensive larvicidal and drainage program. Camp Paranam and Camp Moengo were served through programs carried out by the local aluminum companies. In general, larvicidal work was instituted whenever field inspection showed the breeding of anophelines.

    At the six bases of the 99-year class, long-range plans as well as emergency measures were, of course, important. Each of these installations is discussed separately in the section which follows.

CONTROL PROGRAMS AT BASES UNDER LONG-TERM LEASE ¹⁴¹

    Edinburgh Air Base, Trinidad, B.W.I. - Drainage for malaria control could not be accomplished until general purpose drainage had been completed, and this was slow. Larvicidal control within the base, however, was excellent. Beginning in September 1943, the base was operated by Navy personnel, and the 80th Construction Battalion was assigned there. As long as Army personnel remained at this establishment, a cooperative program of mosquito control was in effect. The 80th Construction Battalion provided necessary equipment, such as dragline and bulldozer, while the post engineer furnished larvicidal control and labor to man the equipment.

¹⁴¹  Annual  Report, Surgeon, Trinidad Sector and Base Command, 1943

    Port of Spain, Trinidad, B.W.I. - The post extended for about a mile along the Port of Spain waterfront and ranged from one-quarter to one-half a mile wide. Normal filling and grading took care of all greater breeding areas, and larvicidal work covered the rest. To protect adequately all parts of the post, permission was secured to extend control measures into British property known as the Kings wharf area. Control appears to have been nearly complete. For months at a time, inspectors were unable to find anopheline larvae.

    Green Hill Cantonment, Trinidad, B.W.I. - This cantonment suffered a high malarial rate in 1942. A large, coastal swamp, closely adjacent, was the source of the anopheline vector. Accordingly, in February 1943, the district engineer was directed to provide a nonclogging, self-cleansing outlet from the swamp to the ocean and to install a tide gate. This was completed in July 1943, leaving the swamp entirely dry.

    Green Hill Cantonment was built in a coconut plantation. This resulted in ditch maintenance being more expensive than usual for a post this size. In spite of this, excellent standards were maintained.

    Fort Read, Trinidad, B.W.I. - It was not until April 1943 that a larviciding program was started for the control of ground-breeding mosquitoes. Earlier in the year, it was believed that the tree-breeding A. bellator was the only malaria vector of consequence in the vicinity. The disclosure by the field inspection program that A. aquasalis was breeding extensively nearby caused considerable revision of control procedures. It was found that not only was this species present in the salt marshes 13 miles away but that it had adapted itself to a salt-free environment and was breeding successfully in fresh water pools throughout the Fort Read area (fig. 28). It then became necessary to cover approximately 25 square miles of territory with larvicide each 7-day period. A Sanitary Corps officer was assigned to cooperate with the staff of the post engineer in carrying out this program. There was a lack of labor, transportation, and of competent supervision, but these problems were gradually solved, and, by 1 September 1943, good control over ground-breeding mosquitoes had been achieved. Minor drainage projects were carried out here and there to eliminate repeated larviciding.

    As for the control of A. bellator, because of delay in the shipping of high-pressure spray machinery, it became necessary to resort to a hand-cutting program for the elimination of bromeliads. During the last 3 months of 1943, a strip, nowhere less than one-quarter mile wide, was cleared around all cantonment areas. This involved climbing some 70,000 immortelle trees. An allotment of $102,000 from Headquarters, Caribbean Defense Command, was nearly all used for this purpose.

    British Guiana Base Command. - An excellent program was initiated in 1942 and supplemented in 1943 by a certain amount of new ditching to connect several springs and streamlets with the main outfall. The maintenance of the system, however, proved excessively expensive. In 1944, steps

FIGURE 28. - Dawn trap used in mosquito survey at Fort Read, Trinidad, B.W.I.

were taken toward the installation of permanent tidal gates which would prevent tidal water from entering areas adjacent to the Demerara River. Homemade tidal gates had been in operation on all outfall drains fronting the river since 1942.

    Saint Lucia Base Command. - Much swamp filling, drainage, and clearing work were accomplished during the construction period. Subsequent extension of the drainage and filling, together with a well-administered larvicidal program, made Saint Lucia relatively mosquito free in 1943. It was only necessary to extend the permanent construction work to cut down maintenance costs.

    The incidence of malaria among military personnel on Saint Lucia in 1943 was approximately 45 per 1,000 per annum; by 1944, this had been reduced to 8 per 1,000 per annum. Flushing of certain swamps with sea water and emphasis on individual protective measures were considered responsible for a good share of the improvement.

Special Units, Organizations, and Projects

    Caribbean Health Service during construction of bases .- The London treaty of 27 March 1941, confirming an exchange of notes, dated 2 September 1940, gave the United States 99-year leases to sites in British possessions for

the construction of Army, Navy, and Air Force Bases. The sites were located in Newfoundland, the Bermudas, the Bahama Islands, British West Indies, Jamaica, Antigua, Saint Lucia, Trinidad, and British Guiana.¹⁴² It will be seen that the majority of these locations fell in malarious territory.

    Construction of these bases became the responsibility of the Corps of Engineers, U.S. Army, and an Eastern Division, Corps of Engineers, was created to carry out this work. In the Caribbean, the work was carried on by districts which did not always have the same boundaries or designations throughout the war. For example, the Jamaican District, at one time distinct, came under the Puerto Rican District in 1943. The Army Air Base in Antigua, most southerly project of the Puerto Rican District in 1942, appears in later documents as falling in the Trinidad District along with Saint Lucia and British Guiana.

    The medical officers who first served each base deserve great credit for their comprehension of the malaria problem and for their early attention to preventive sanitation.

    The special problem in Trinidad, relating to malaria transmission by A. bellator, breeder in bromeliads, in treetops, was investigated and eventually controlled.

    Malaria attack rates for the Caribbean area in 1942 ranged between 50 and 180 per year per 1,000 average strength as compared, for example, with the low and high attack rates in Liberia, 429 for September and 1,340 for December 1942, respectively. ¹⁴³ It was found difficult to protect troops away from fixed installations or troops newly arrived in a highly malarious area where they must live under field conditions while constructing a base. The relative success achieved in keeping Caribbean rates within bounds would seem to be due in no small part to the fact that, in general, bases were completed by small groups of engineers and other professional personnel, using much native labor, before substantial numbers of military personnel were brought there.

    The Engineer Service, Caribbean Defense Command, took a firm attitude regarding malaria prevention in 1941- 42.¹⁴⁴  Regulations were posted and rigidly enforced. These pertained to use of bed nets, quinine prophylaxis, mosquitoproofing of barracks, use of insecticide spray, individual protective measures, care of tin cans, discouragement of excessive use of alcohol, maintenance of drainage ditches, and oiling of breeding places. In general, it can be said that the work of construction was not seriously hampered by the malarial rate prevalent in the labor force.

¹⁴² See footnote 96, p. 205.
¹⁴³ Rehn, John W. H: Malaria, Its Prevalence, Control, and Prevention in the Africa-Middle East Area. [Official record.]
¹⁴⁴ Medical History of the Panama Division, Engineer Service, Caribbean Defense Command, 1941-42.

    The 392d Medical Malaria Control Detachment. - For the southern half of the Antilles Department, the history of malaria control is very largely the history of the 392d Medical Malaria Control Detachment.¹⁴⁵

    This organization, referred to in most documents as the "Malaria Laboratory," serviced Trinidad, Saint Lucia, British Guiana, Surinam, and French Guiana. There were a number of changes, both in organization and in personnel between its inception in 1942 and the end of 1944, but, as of 1 November 1944, the organization became known as the 392d Medical Composite Unit (Malaria Control). On 21 March 1945, the name was changed to 392d Medical Malaria Control Detachment. The commanding officer of the laboratory served also as the sector malaria control officer, or assistant Department malaria control officer, or, during the period when the laboratory served only Trinidad, as the base malaria control officer.

    Commanding officers of the Malaria Laboratory were as follows: Capt. Melvin D. Robinson, MC, arrived 9 March 1943, departed 19 December 1943; Capt. Eli C. Ridgway, MC, arrived 23 December 1943, departed 9 March 1945; Capt. (later Maj.) Donald C. Senges, SnC, arrived 26 April 1945, departed 15 November 1945; and 2d Lt. Stanley F. Yolles, SnC, November 1945 through 10 January 1946. The parasitologist was Mrs. Tamarath K. Yolles, from the opening of the laboratory in 15 January 1943 to December 1945; the entomologist, Lieutenant Yolles, from the opening of the laboratory, 15 January 1943 to January 1946. Slides on all cases of malaria reported from all hospitals in the sector were checked in this laboratory. An able group of enlisted technicians operated an insectary, identified entomological specimens, maintained records and files, performed necessary chemical work, and assisted in malaria control activities. Two of these technicians functioned on detached service at the British Guiana Base Command.

    First located in Saint Clair cantonment, immediately adjacent to the office of the sector surgeon, the Malaria Laboratory was moved to Fort Read, 12 May 1944, where more space and better facilities were available. Added office space, a classroom, an animal house, and a dressing room for native dippers were among the features provided. From the inception of the laboratory until activities were transferred to Fort Read, continuous courses were given for all medical officers arriving in the area, also for selected groups of nurses. Instruction concerned the diagnosis and treatment of malaria, as well as the identification of anopheline and culicine mosquitoes.

    Beginning 3 May 1943, the sector Malaria Laboratory initiated a course for enlisted technicians in the laboratory diagnosis of malaria. Thick smear technique was emphasized. Surgeons at the various posts were urged to select personnel and recommend them for this training.

    All hospitals in the sector were required to submit a thick and a thin blood smear on each case diagnosed as malaria. These were stained and examined in the sector Malaria Laboratory, and reports were made to the hospitals.

¹⁴⁵ Annual Report, 392d Medical Malaria Control Detachment, 1942-45.

    Consistently recurring error from any station was indication for sending the station technician to the sector Malaria Laboratory for intensive training in slide diagnosis. This practice resulted in a great reduction in percentage of error.

    The central organization maintained a slide library of all malaria patients in the sector. Each incoming case was recorded on an organizational chart which provided a running picture of malaria control efficiency for each location as well as for the sector as a whole.

    Most of the malaria in the Trinidad Sector was of vivax type. The 1943 annual report from this sector shows P. malariae occurring in negligible amount, but throughout 1943 the percentage caused by P. falciparum gradually increased from 13.8 percent in January to 33.3 percent in November. There was a corresponding decrease in the percentage of vivax cases, from 86.3 to 64.9. Typical of attempts to reduce human reservoirs was a malaria survey conducted at Green Hill Cantonment on 500 natives living near the base. Any person with a positive spleen or positive blood smear was treated with Atabrine.

    The entomological aspects of the work of the sector Malaria Laboratory deserve special comment. Continuous larval surveys were carried on at each base, as were weekly adult mosquito collections. Enlisted men of either the Corps of Engineers or the Medical Department supervised the native collectors. These were guided by a simple, nontechnical manual, which explained methods of collecting, packing, and shipping of adult and larval specimens. Identification work was performed at the sector Malaria Laboratory, to which all collected specimens were sent. Collectors were required to fill out data forms, thus contributing to knowledge of breeding, feeding, and resting habits. Identifications were reported back to the surgeon of the base concerned, with comments on the relative importance of the species and preferred methods of control.

    Many inspections and surveys were made by the malariologist and by the parasitologist, also by the engineer, separately or in combination with the entomologist. These involved areas in British Guiana, Surinam, French Guiana, Saint Lucia, and Trinidad.

    Other sanitary agencies. - Antilles Department medical laboratory at San Juan, shared with the 392d Medical Malaria Control Laboratory, at Fort Read, the credit for considerable research work related to sanitation.¹⁴⁶ A third agency, the Anglo-American Caribbean Commission, also deserves comment in this connection:

    This body was created on 9 March 1943 for the purpose of encouraging and strengthening social and economic cooperation between the United States of America and its possessions and bases in the area known geographically and politically as the Caribbean area, and the United Kingdom and British Colonies in the same area, and to avoid unnecessary duplication of research in these fields *  *  *

¹⁴⁶ A History of Medical Department Activities in the Caribbean Defense Command in World War II, vol. 3.

    The agency was located in Trinidad, at Port of Spain. General health and living conditions received considerable attention on the part of this advisory group, which consisted of three members from each of the two countries. Its relation to malaria and malaria control was indirect, through its interest in the overall program of sanitation.

    Airplane dispersal of DDT in the Antilles Department. - Larviciding by means of airplanes had been undertaken with some success before the availability of DDT. At Losey Field, plane dusting with a paris green mix was used to treat a second growth mangrove swamp in the extra reservation area in 1942; L-1 or L-4 observation biplanes were used. A similar procedure was followed in 1943 to protect the Navy San Patricio housing development, along with Fort Buchanan which was nearby. A Navy "duck" (amphibian) plane was first employed, but it could not fly low enough because of its pontoons. A "moth" monocoupe was later substituted, with better results. Caking of the mix, deterioration of paris green, and variable breezes, even in the early morning, accounted for wide variation in the control achieved, but the experience was valuable.

    Operations using DDT were first carried on at Camp Tortuguero, and (somewhat later) at Fort Bundy. At Fort Bundy, the breeding areas were off the post, in mangrove swamps and jungle, and included portions of the Las Palmas river valley and the Río Daguao valley, where ground larviciding measures had not proved successful.

    After initial trials, reliance was placed chiefly on airplane application, supplemented by hand dusting and minor drainage. Before this, in the wet season, control was never satisfactory, and malaria in civilian laborers had somewhat handicapped the construction of the base. In spite of extensive larviciding, bait trap catches of A. albimanus had ranged up to 144 per night, per trap. The substitution of airplane spraying for all other control procedures in the Río Daguao valley and lower mangrove portion of the Las Palmas river valley achieved remarkable and gratifying results.

    Several points were established which were of great interest at the time:
    1. Spraying of DDT in diesel oil can be carried out in wind up. to 18 to 20 miles per hour. This is impossible with paris green dusting.
    2. Eight to ten trips per day, in familiar areas, constitute the normal service which might be expected of one pilot, using an L-4 Cub type airplane. (In actual practice, the usual number of trips per day was five or six.)
    3. This provides for a daily coverage of 1,000 acres and spreads from 200 to 250 gallons of spray solution. (When the formulation became stabilized at 5 percent DDT in diesel oil, the rate of application was one-half gallon or more per acre.)
    4. A swath 30 feet wide can be satisfactorily treated by flying 15 feet above the mangrove, in moderate wind.
    5. Larvicidal action remained in effect about 5 days.

    In mid-February 1945, there were moderately heavy rains at Fort Bundy. Under former control programs, this would have led to a rise in mosquito densities. However, efficient pumping and drainage systems were then in operation, and there was also an application of DDT in diesel oil by the L-4 Piper Cub. As a result of these combined measures, trap collections during the last week of the month averaged only 0.6 specimens. During certain months, the operation of the light plane was hampered somewhat by the frequency of strong winds; nevertheless, low bait trap collections were maintained.¹⁴⁷

    Even first results at Fort Bundy were so promising that the program was expanded to include Fort Read, Fort Simonds, and Atkinson Field. Some spraying was done with 10 percent DDT in diesel oil, but, in most of the applications, a 5-percent solution was used. One quart of solution, equivalent to 0.1 pound of DDT per acre, proved adequate.

    Early applications were made with an L-4 Piper Cub plane, equipped with a Husman-Longcoy spray apparatus. Later, a larger liaison-type L-1 plane was used and finally a C-47, capable of carrying two removable 250-gallon tanks. Intervals between spray operations varied from 3 to 8 weeks or longer, depending on anopheline density and the nature of the season and terrain. In all cases, however, excellent control was achieved, and, wherever operations were on a sufficient scale to permit the reduction or elimination of ground control activities, very significant savings in costs were realized. At Fort Bundy, a permanent drainage project to cost approximately $277,860 had been canceled, and alternative procedures became mandatory. Aerial larviciding proved to be the answer. In Trinidad, the cancellation of a similar undertaking, estimated to cost $423,000, made aerial larviciding necessary. It was, of course, successful.

    In Trinidad, superior results were obtained by having the pilot cover the area to be treated in a decreasing spiral, rather than in parallel swaths. Two or three spiral flights, starting at the perimeter, were required to disperse the amount of solution allotted for the acreage concerned. This appeared to result in a more even distribution of insecticide than parallel flights.

    The original plan called for the airplane spraying of only some 2,000 acres directly associated with Waller Field. As actually carried out, however, the project included the entire Fort Read area, a tract of approximately 5,000 acres. This was slightly rolling terrain, partially cleared of dense jungle around the various buildings of the post. Scattered through the heavy jungle were more or less cleared areas which functioned as primary breeding sites. Complete, permanent drainage for this acreage would have cost in the vicinity of $2 ¹ /2 million. Control for 1 year, by use of a C-47 type plane, scarcely exceeded $20,000. The degree of efficiency achieved is indicated by a total of only 1.24 Anopheles adults per collection during the peak of the rainy season

¹⁴⁷ Essential Technical Medical Data, Caribbean Defense Command, February and July 1945.

in June. One year before., without airplane spraying, the figure stood at 60.2 adults per collection.

    In territory requiring great maneuverability of the plane, the L-4 and L-1 types were superior, though somewhat more expensive to operate than the C-47.

    As a result of the Department surgeons' inspection of bases in Cuba and Jamaica in December 1945, it was recommended that a second C-47 plane be requested for use in DDT spraying in the Antilles Department. With one plane based at Borinquen Field and the other at Waller Field, it was felt that long flights could be eliminated and that advantage could be taken of optimal weather conditions. Also, in the event of a breakdown, the remaining plane might still continue to serve the area.

    Special studies on methods for dispersal of insecticides by aircraft made use of the 119th and 125th Malaria Control Units which had completed training in Panama, 17 November 1944. The technical assistance of these units proved very valuable. Although originally designated for service in Pacific areas, both units were held in Panama until 15 July 1945, a delay in movement of 3 months over orders previously issued. These units had previously served in the Antilles Department and were attached to the Army School of Malariology on a temporary basis. By General Orders No. 34, Panama Canal Department, they had been redesignated on 2 May 1944, as the 119th and 125th Malaria Control Detachments.

    Recapitulation and comment. - In the Antilles Department, it was necessary to locate many of the bases in low, marginal areas where extensive mosquito breeding was inevitable. Temporary control measures were usually instituted along with first construction operations. Overall plans for the base provided for more permanent control measures.

    In general, malaria rates were high during the first year, gradually dropping to a tolerable level as major engineering operations were completed. In 1944, it was possible for many posts to maintain satisfactory control with routine preventive practices and a larviciding program. In the same year, the use of the airplane for dispersal of DDT made possible the treatment of areas hitherto inaccessible and greatly cut the labor cost in many localities where a large labor force had previously been required. An airplane can cover in a few hours territory which requires days to treat with ordinary ground equipment. Certain costly, permanent work which had long been planned was postponed or abandoned in favor of treatment from the air. Although many biological scientists have seriously questioned the ultimate effect of continued air dispersal of DDT on the fauna and flora of the regions involved, there can be no doubt that economic advantage clearly justified this procedure during the latter portion of the war.

    As discussed previously, most of the preliminary work with airplane dispersal was conducted at Fort Bundy. With former methods, in spite of the

combined programs of the Army and the U.S. Public Health Service, animal bait traps located on swamp margins continued to give anopheline catches that were undesirably high. For a brief period, this reached over 1,000 specimens per night owing to heavy rainfall. Salinization ditches were used to reduce breeding in a mangrove swamp to the south of the base, and a pasture, directly west, was served by a pumping station with a drainage and diking system. Aerial larviciding was employed as an added measure, especially over mangrove swamps lying to the southwest. When an uninterrupted 7-day cycle was maintained, the anopheline catch remained close to zero. Similar results were obtained by the Navy in treating the Brugal Swamp, near San Juan.

    Spraying of the walls and ceilings of native huts on or near military areas with 5 percent DDT in kerosene was also tried. This, of course, was aimed at reducing the number of infected mosquitoes. Surfaces so treated retained their toxicity for at least 2 months.

    Older insecticides were also made effective by improved techniques. U.S. Public Health Service personnel developed oil emulsions to replace straight oil as a larvicide. More. effective and less costly, the emulsion larvicide was much used at Losey Field, where an M-4 chemical warfare apparatus was employed in its preparation.

PROBLEMS OF U.S. ARMY AIR FORCES IN THE CARIBBEAN DEFENSE COMMAND

Sixth Air Force ¹⁴⁸

    The predecessor of the Sixth Air Force was the 19th Composite Wing, which had been activated in 1929 and was stationed at France Field, on the. Atlantic side of the Canal Zone. The airbase at Albrook Field, on the Pacific side, was opened in 1932. During the 1930's, all medical service to these troops was provided by officers and men on duty in the PCD and assigned either to Albrook or France Field.

    Approximately 40 emergency landing fields were available in the Canal Zone and Republic of Panama. Some of these were merely unimproved pasture lands, but others, with various improvements, became of military importance, with attendant medical problems. Some time was to elapse, however, before the idea of establishing a ring of outlying bases changed the basic concept of defense from that of destroying planes over the Canal Zone to one of preventing any enemy from coming within striking distance of it.

    To develop needed additional airbases, and to service them, the Service Command, Caribbean Air Force, was brought into being on 18 September 1941.

¹⁴⁸ Except as otherwise indicated, all data in this section have been compiled from the Medical History of the Sixth Air Force, 1929-42.

One week later, three Service Area Commands were established; namely, the Panama Service Area Command, the Puerto Rico Service Area Command, and the Trinidad Service Area Command. The Service Command had control of all Air Corps Stations, Air Corps Bases, and Air Depots in the Caribbean Defense Command, including all service personnel, service units, and fixed installations thereon located. Combat units were thus left free to engage in training or fighting, as occasion might demand. As a matter of record, it should be stated that the Panama Area Service Command never operated under an approved table of organization and was eventually absorbed by the Service Command itself.

    Under a reorganization in February 1940, the 19th Composite Wing was made to include the Panama Air Depot, in addition to a number of newly activated units. The first use of the term "Air Force," in connection with these units was in November 1940, when the Panama Canal Department Air Force was activated and assigned to Albrook Field. Certain Signal and Ordnance Corps components were included, in addition to all units making up the 19th Composite Wing. Maj. William B. Wilson, MC, was designated on 27 January 1941 as Surgeon, Panama Canal Department Air Force.

    Major Wilson was replaced by Lt. Col. Ernest F. Harrison, MC, who arrived in Panama, 19 October 1941, and was announced as Surgeon, Caribbean Air Force, 2 days later. Maj. (later Col.) John B. Herman, MC, formerly Surgeon, Albrook Field, became assistant surgeon. Practically all of the planning, organization, and supervision of medical services during 1942 fell to these two officers. This was, of course, the year of greatest expansion and development. In February 1942, Colonel Harrison visited, in person, Curaçao, Aruba, Trinidad, Surinam, Saint Lucia, Antigua, Saint Croix, Puerto Rico, the Dominican Republic, Haiti, Cuba, Guatemala, Nicaragua, and Costa Rica.

    The subsequent history of the Panama Canal Department Air Force was as an integral part of the newly formed Caribbean Defense Command, the headquarters of which were activated 8 May 1941, at Quarry Heights. All Air Forces of the Panama Canal Department, together with those of the Puerto Rican Department and the Trinidad Base Command, were immediately combined into the Caribbean Air Force.

    Because the Caribbean Air Force had been given practical autonomy by the commanding general of the Caribbean Defense Command, it became necessary to clarify the division of medical responsibility. In February 1942, the Army Ground Forces of the Panama Canal Department, Puerto Rican Department, and Trinidad Base Command retained responsibility for environmental sanitation, veterinary inspections, all quarantine measures, new water supply projects, medical supply and related inspections, and also for general hospitalization and evacuation to general hospitals.

    All other medical service of the Air Force operated independently for the next year and a half. It will be seen that long-range, permanent projects for malaria control remained in the hands of the Army Ground Forces which were responsible for "environmental sanitation."

    On 6 March 1942, the Caribbean Air Force was redesignated the Sixth Air Force. Colonel Harrison, as surgeon, headed the medical section of that headquarters.

    The Trinidad and Puerto Rican areas required the Air Force to face a more serious malaria problem than had been encountered in Panama. Whereas permanent drainage, filling, and construction projects had rendered the Canal Zone relatively safe, a large number of new stations and outposts throughout the Antilles were being established in wholly unsanitated surroundings, insofar as malaria was concerned. In some regions, 80 percent of the native population were infected. It is not strange that the primary malaria rate skyrocketed from the old average of 70 per 1,000 per annum (Panama Canal Department) for the years 1940 and 1941 to a peak in June 1942 of 233 per 1,000 per annum in military personnel.

    During this year, numerous airbases, airdromes, and air warning outposts were established. This defense system involved Air Force installations from Guatemala to Peru and from the Greater and Lesser Antilles to the Galápagos Islands in the Pacific. The Panama Area included airbases at Albrook Field, Howard Field, France Field, Rio Hate, Guatemala City, Salinas, Ecuador, Galápagos Islands, and David, R. de P., with auxiliary airdromes at Chame, Aguadulce, La Chorrera, and La Joya, all in the Panamanian Republic.

    The Puerto Rican Area included the airbases at Borinquen Field, Losey Field, Benedict Field, and Coolidge Field.

    The Trinidad Area included airbases at Waller Field, Beane Field, Hato Field, Zanderij Field, and Atkinson Field.

    The further establishment of numerous aircraft warning stations made the malaria problem much more real. Many of these were quite isolated and could only be reached by boat, after a 48-hour trip. Organization of the Medical Detachment, 558th Signal Aircraft Warning Battalion, dated from 7 March 1942. When this battalion was disbanded and replaced by the 516th Signal Aircraft Warning Regiment, the Medical Detachment was increased to 9 officers and 67 enlisted men (eventually to 93). Dispensaries were operated at Howard Field, Quarry Heights, and Fort Gulick.

    By September 1943, evacuation facilities had been much improved, permitting the medical officers to spend more time on inspection trips and the supervision of sanitary maintenance. As a result, the incidence of malaria was reduced to rates comparable to those found in more sanitated areas. In accordance with published orders, Atabrine prophylaxis was discontinued in October 1944. It was believed that the malaria rate did not increase., because of the vigilance of the men in carrying out all other measures for malaria prevention.

As an outgrowth of the organizations listed above, the 554th Signal Aircraft Warning Battalion was activated 25 November 1944.

    The Medical Service of the Sixth Air Force inevitably became interested in the dispersal of DDT from airplanes for the control of insect vectors of disease. Various tests and achievements within the territory of the Caribbean Defense Command have been discussed previously. These results, and similar reports of success in many theaters, led the Office of the Air Surgeon, Washington, D.C., to propose the activation and training of Air Force insect control units. Such units were to consist of certain experienced flying personnel trained in low-level flying, together with malariologists, entomologists, and sanitary engineers, in addition to necessary ground and supporting elements.¹⁴⁹ Notice to this effect was sent the surgeon of the Sixth Air Force on 3 May 1945. It is not known if any such units were ever activated for service in the Caribbean Defense Command.

The Air Transport Command

    The Caribbean Wing (later redesignated the Caribbean Division) of the Air Transport Command became of greatest importance during the latter half of the war. It had its malaria problems, but, being forewarned, was fore-armed and of course made use of well-developed and already sanitated facilities. Excellent general malaria control and individual discipline were reported from Atkinson Field, ¹⁵⁰ only two cases of malaria having occurred over an extended period. The flight surgeon carried on a program of medical education here as at other bases. Transient personnel were briefed daily with particular stress on malaria. Suppressive treatment, individual preventive measures, and the use of the Aerosol bomb were given emphasis. A 4-hour malaria course for officers and enlisted men was repeated every few months.

    At Waller Field, only one case of malaria was reported during 3 months. Bed nets were required and barracks were sprayed, though the efficiency of the latter might be doubted as, at first, open barracks prevailed and only Aerosol insecticide was available for much of the time. Spraying time was increased in an attempt to compensate for this. For the last 3 months of 1944, there was no malaria among Air Transport Command personnel at Waller Field. As reported on 1 January 1945, mosquitoes were few, a reflection of the efficiency of the insect control program. The post was well drained, the barracks well screened, all screens were inspected at least once a week, and a continuous program of oiling, spraying, and clearing was in operation.¹⁵¹

 ¹⁴⁹ Letter, Brig. Gen. Charles R. Glenn, Deputy, The Air Surgeon, to Surgeon, Sixth Air Force, 3 May 1945, subject: Transmittal of T/O and T/E for Insect Control Unit.
¹⁵⁰ Medical Historical Report, Caribbean Wing, Air Transport Command, From Its Inception through 30 June 1944, subject: Medical Problems, Atkinson Field, British Guiana.
¹⁵¹ Medical Historical Report, Caribbean Division, Air Transport Command, 1 July-30 Sept. 1944, subject: Malaria, 11O7th AAF Base Unit, Waller Field, Trinidad.

The Caribbean Air Command, 1946

    The malaria rates among personnel in the Caribbean Air Command for September 1946 are shown in the following tabulation:

Unit (including subbases )                                                           Rate per 1,000 per annum
                                                                                                              (all recurrent)
Albrook........................................................................................................5.1
Howard........................................................................................................5.6
France........................................................................................................21.1
Borinquen.....................................................................................................6.5
Panama Coastal Frontier...............................................................................5.2
Caribbean Coastal Frontier...........................................................................4.3
Entire Command...........................................................................................4.72

    No clinical malaria was present at the Panama Air Depot, Rio Hato, Beane Field, Coolidge Field, Vernam Field, Atkinson Field, Waller Field, or their satellites.

    It will be noted that no primary malaria occurred. During the previous month (August 1946), the primary rate for the Caribbean Air Command was 5.6; for September 1945, it had been 9.6.

    The good results shown in this particular report reflected the assumption of part of the control work by post engineers. This work had previously been performed by hiring laborers who were paid out of Medical Department funds.

    Airplane spraying of DDT was also beginning to make itself felt. By this time, such procedure had become routine at Howard Field, France Field, and Rio Hato Air Field in the Panama coastal frontier area. In the Caribbean coastal frontier area, airplane spraying was being used when necessary. At all outpost stations, individual protection was emphasized.

COOPERATING ORGANIZATIONS (NONMILITARY)

The Rockefeller Foundation

    The history of malaria control in this area during the war years was intimately involved with the previous and continuing activities of the International Health Division of the Rockefeller Foundation.¹⁵² Malaria surveys, field studies, and control activities were carried out in Puerto Rico from 1920 to 1936. In 1924 and from 1940 to 1943, surveys and field studies were conducted by the Foundation in Haiti. From 1928 to 1933, Jamaica had received similar attention. There were Foundation malaria projects in Costa Rica, 1928-40; Honduras, 1927; Nicaragua, 1920-25; Panama, 1926-39; El Salvador, 1934-42; Cuba, 1935-42; British Guiana, 1938-46; Trinidad, 1941-46; and Colombia, 1929, 1932-48.

¹⁵² Annual Reports, Rockefeller Foundation, 1920-1948

U.S. Public Health Service - Malaria Control in War Areas ¹⁵³

    The office of MCWA was established in February 1942 ¹⁵⁴ to organize a control program which would utilize the resources of the Work Projects Administration and State health departments, supplemented by direct operations on the part of the U.S. Public Health Service when other resources were inadequate. Control work outside military reservations was closely integrated with that carried on by military authorities within the boundaries of the various posts. Operations began 17 March 1942.

    Insofar as the Caribbean Defense Command was concerned, activities centered in Puerto Rico and, to a lesser extent, in Jamaica.

    By the end of 1941, the Navy had begun the vast Roosevelt Roads Naval Base, and Puerto Rico became strategically important in many ways. It was a base for antisubmarine operation by both sea and air.¹⁵⁵ Military installations were located for tactical and strategic purposes, of course, and this usually involved localities where both hyperendemic malaria and infected mosquitoes were to be found. All Army posts except Borinquen Field were poorly located in this respect, as were the two major naval bases at Ensenada Honda and Vieques. Night duty was especially hazardous at coast artillery, searchlight, and antiaircraft installations. One-third of the first group of marines sent to Vieques island came down with malaria within 3 months after landing there.

    During 1941, an attempt was made, utilizing Work Projects Administration labor, to carry out antimalaria work near military bases. This effort, sponsored chiefly by the Insular Health Department, came to very little because of material and equipment shortages and lack of trained personnel. The malaria attack rate in military personnel continued to rise.

    When MCWA began operations in Puerto Rico, it was agreed with the Insular Health Department that all antianopheline projects around military bases would be carried out directly by the U.S. Public Health Service. This enabled local funds to be concentrated chiefly on malaria control in rural areas and civilian population centers, with particular emphasis on the provision of antimalarial drugs.

    Malaria Control in War Areas confined its first work to the vicinity of the four major Army posts and the two naval bases mentioned previously. The Army posts were Fort Buchanan, Losey Field, Camp O'Reilly, and Camp Tortuguero. The Army and Navy did as much intracantonment work as possible, while the U.S. Public Health Service devoted itself primarily to extra-cantonment activities. ¹⁵⁶

¹⁵³ Much additional information concerning Malaria Control in War Areas is scattered throughout other portions of this section and need not be duplicated here.
¹⁵⁴ Malaria Control in War Areas, 1942-43, p. 34. In Summary of Activities, Office of Malaria Control in War Areas, The Public Health Service, 1943-46.
¹⁵⁵ Pratt, H. D., and Stephens, P. A.: History of MCWA Operations in Puerto Rico, 1942-1946. [Official record.]
¹⁵⁶ Bolten, J.: The Prevention of Malaria Among the Military Forces in Puerto Rico. Bol. Asoc. méd. Puerto Rico 35 : 89-96, March 1943.

    Four types of extracantonment control were available, all calculated to reduce the numbers of mosquito larvae. These were the (1) use of paris green (a stomach poison), (2) use of oil (acts primarily on respiratory organs), (3) drainage projects (designed to remove water before a generation of mosquitoes can be produced), and (4) filling operations (to eliminate depressions in which water often stands).

    Manmade breeding places were very common. At Fort Buchanan, the incidental filling of drainage ways had caused flooding into old pasture lands, sugarcane fields, and mangrove swamps. At Camp O'Reilly, a network of roads without culverts) at the very center of the encampment had dammed the ditches and thus formed breeding places, while borrow pits and old stream channels, not filled in, produced mosquitoes in the immediate vicinity of the barracks. At Ensenada Honda, also, roadbuilding and general leveling had blocked many drainage courses, and the constant efforts of over a hundred laborers were required to keep conditions from becoming a menace.

    At Fort Buchanan and Losey Field, subsoil tile was first employed in drainage projects. Later, however, centrifugal pumps were used in low-lying areas, not only to lift water from below sea level but also to facilitate drainage from land not more than 3 feet above sea level. The water was led off through large, open, outfall canals.

    Larviciding crews were employed in the afternoons on minor drainage work, whenever winds became too strong to do effective dusting with paris green. During the more active breeding season, water was not allowed to go undrained or untreated in any place for more than a week, as this time represented the development period of a mosquito generation under favorable conditions; 2 days for the eggs, 1 day for each of the four larval stages, and 1 day for the pupa.

    It was difficult to evaluate the merits of larviciding and drainage as compared with measures aimed directly at the adult mosquito. Because of improvements in types of mosquito traps, nightly counts of captured adult anophelines sometimes rose, even when field control conditions were becoming increasingly effective. Certainly the "safe index" under one set of conditions cannot be taken as reliable in another setting, though the MCWA did use an index of "5" as a tentative aiming point for keeping malaria at a minimal

    Mosquitoproofing of barracks, supplemented by spray killing of the few mosquitoes which succeeded in entering buildings, must receive a great deal of credit for reducing malaria transmission but only in partnership with attacks made concurrently on the breeding grounds of the vector hosts. It would be unfair to state that antiadult procedures were chiefly responsible for marked

¹⁵⁷ Henderson, J. M. Antimalaria Measures for the Protection of Military Personnel in Puerto Rico and Their Applicability to Civilian Malaria Control. Puerto Rico J. Pub. Health & Trop. Med. 20: 419-445, June 1945.

decreases in the incidence of malaria among the troops. Also important is the fact that apparent decreases in malaria usually needed interpretation. Early morbidity reports did not distinguish between primary attacks and recurrent conditions, whereas later reports did. Intelligent comparisons required careful study.

    A point of interest brought out in the Bolten report ¹⁵⁸ is that larviciding, usually advocated where drainage cannot yet be undertaken, was rarely effective in Puerto Rico until after a certain amount of preliminary drainage had been accomplished. This reduced the breeding areas to a point where real control might be accomplished with the facilities available. Otherwise, in spite of a good larvae kill (90 percent with paris green), materials and labor were often wasted.

    A malaria board was formed, consisting of the Antilles Department malaria control officer, a representative of the Corps of Engineers, U.S. Army, and the Chief of Operations, MCWA. This board visited various U.S. Army posts throughout the Caribbean, including those in leased territory One outcome of this visit was the institution of an extracantonment program in the vicinity of Fort Simonds in 1944. Unusual rainfall late in 1945 created a special problem here, which was met by weekly spraying from the air with 5 percent DDT in diesel oil, utilizing a plane based on Borinquen Field.

    In 1945, the U.S. Public Health Service carried out an urban malaria control project at Ponce in cooperation with the Insular Health Department and the Puerto Rican Work Projects Administration. The next year saw a DDT residual spray project at Santa Isabel.¹⁵⁹

    The MCWA field station in Puerto Rico rendered monthly reports on its activities for the entire period, 1942-45. These were submitted to the Division of States Relations, U.S. Public Health Service, until that Division became part of the Bureau of State Services, after which reports were sent to that office.

    In the fall of 1945, the MCWA notified both the Army and the Navy that it proposed to close out its operations in Puerto Rico. Both arms of the service, however, requested that the U.S. Public Health Service continue its operations, modified in accordance with need and availability of funds. This was approved by the Federal Security Administrator, after which a joint malaria control organization was established. The administrative body was the Joint Army-Navy-Air Force-U.S. Public Health Service Malaria Control Committee, to be known later as the Joint Army-Navy-Air Force-U.S. Public Health Service Malaria Control Board. This agency continued to function until about midyear 1950. The coordination of intracantonment and extracantonment activities under this arrangement appears to have been excellent.¹⁶⁰

    After the war, the "Malaria Control in War Areas Program" of the U.S. Public Health Service was superseded by the "Extended Malaria Control Pro-

¹⁵⁸ See footnote 156. p. 241.
¹⁵⁹ See footnote 155, p. 241.
¹⁶⁰Annual Report, Surgeon, U.S. Army Forces, Antilles, 1949.

grain." ¹⁶¹ Whereas the first was calculated to protect military personnel from malaria indigenous in war areas, the second was devised to forestall the possibility of the transmission of malaria from returning servicemen to civilian populations. Residual spraying of houses with DDT was undertaken in Puerto Rico on an experimental basis. The village of Playa de Humacao was sprayed three times at intervals of 6 months. Blood film surveys over the period concerned showed a drop in positive percentage from 5.8 in November 1944 to 0.9 in November 1945. In the unsprayed village of Loiza Aldea, the percentages were 4.7 and 3.8, on corresponding dates. These desirable results of the residual spray program are all the more striking since A. albimanus, the principal vector, seldom remains within houses except for a few hours during the night and thus has no extended opportunity to acquire a lethal dose of DDT.

Inter-American Cooperative Health Services

    A force affecting at least indirectly both the health of troops and the health of civilian labor in the American Tropics was the Institute of Inter-American Affairs. Key defense areas and those producing critical war materials received particular attention.¹⁶² The establishment and supervision of airbases, the protection of rubber workers in the Amazon, and the sanitation of camps for highway and railroad workers all furnished occasion for activity, especially in the field of malaria control.

    The malaria program was part of a concentrated health campaign entered upon jointly by 18 American Republics, including the United States. At a meeting of American foreign ministers in January 1952, the importance of the mobilization of vital forces was recognized, and, 1 month later, the Health and Sanitation Division was established in the Office of the Coordinator of Inter-American Affairs. It became the responsibility of this Division to extend and amplify the work done by the Rockefeller Foundation (International Health Division) and the consultant services of the Pan-American Sanitary Bureau.

    The Institute of Inter-American Affairs was a corporate unity, set up by the Coordinator of Inter-American Affairs to administer funds and execute cooperative agreements between the United States and other American Republics. Funds, voted by the U.S. Congress, were assigned to the Institute for administration. By mutual agreement, each republic formed a cooperative health service, as an integral part of its National Department of Health. Any project, such as malaria control, was the joint responsibility of the field representative of the Health and Sanitation Division of the Institute of InterAmerican Affairs and a representative of the National Department of Health of the republic concerned. Technical field parties sent from the United States

¹⁶¹ Link, V, B.: A Preliminary Report on Malaria Control by DDT Residual Spraying. J. Nat. Malaria Soc. 6: 124-130, June 1947.
¹⁶² Dunham, G. C. : Malaria Control Activities of the Institute of Inter-American Affairs. J. Nat Malaria Soc. 3: 31-38, March 1944.

were supplemented by local personnel. Funds and equipment were also supplied from both sources.

    Towns in the Republic of Panama which lay along the Inter-American Highway and the Trans-Isthmian Highway received malaria control sanitation under a continuing project directed by the Chief Health Officer, the Panama Canal. In that connection, the Chief Health Officer acted as representative of the Office of the Coordinator of Inter-American Affairs. The benefit to the military was obvious, as many of these towns were close to military installations, and were visited frequently. Two objectives were sought: the reduction of the gametocyte reservoir and the reduction of the adult anopheline vector population.

    Though conceived in response to an emergency situation, the machinery set up by the Inter-American Cooperative Public Health Services was destined to develop a pattern for continued, cooperative effort in the field of international public health. The translation into Portuguese of "Practical Malariology,"¹⁶³ a National Research Council publication, for the benefit of malariologists working in Brazil, is an example of postwar activity on the part of the Institute of Inter-American Affairs.

MISCELLANEOUS MATTERS

Allocation of DDT

    When DDT was available in pounds, rather than tons,¹⁶⁴ very careful calculations were made to insure a fair distribution to all theaters. For example, recommended allotments out of the 50,000 pounds available for larviciding purposes in April 1944 were as follows:

                                                      Pounds                                                                                Pounds
Southwest Pacific...........................12,000                 Caribbean Defense Command..................1,500
South Pacific..................................12,000                 South Atlantic...........................................   500
China-Burma-India.........................10,000                 Central Pacific..........................................   500
North Africa...................................10 000                 Continental United States..........................1,000
Middle East....................................  2,000                 Special use...............................................   500

    The Caribbean and South Atlantic Commands together were thus allotted only 2,000 of the 50,000 pounds, or 4 percent. This does not mean that the malaria problems of these areas had become trivial, but rather that the majority of troops therein were at established posts, protected by permanent control measures, a situation which contrasted sharply with the shifting conditions imposed by combat activities in undeveloped countries.

¹⁶³ See footnote 8 (4), p. 126.
¹⁶⁴ Memorandum, Maj. 0. R. McCoy, MC, Director, Tropical Disease Control Division for the Quartermaster General, attention: Maj. Allan R. Kemp, 30 Mar. 1944, subject: DDT for Mosquito Larvicide Use.

Anopheline Vectors West of the Andes

    On the west coast of South America, three species of Anopheles are important. ¹⁶⁵ Anopheles albimanus occurs mostly below 900 feet but has been recorded from altitudes as high as 5,000 feet. The egg of this species is somewhat resistant to drying and survives at least in the moister mud, throughout the rainless season. Anopheles pseudopunctipennis is never found at sea level. Its range extends from around 300 to something less than 10,000 feet. Anopheles punctimacula is found from sea level to 5,000 feet and is often associated with the culture of rice. As it prefers animals to man, it is responsible for the transmission of human malaria only when relatively abundant.

    In Colombia, ¹⁶⁶  A. darlingi, A. albitarsus, A. punctimacula, A. psuedopunctipennis and A. neivai have been found naturally infected.

    In Peru, A. pseudopunctipennis is the principal vector, but A. punctimacula probably also plays a part.¹⁶⁷ The latter species was known in Peru before 1942 but is now common in the district of Lima and appears to be increasing. Surveys published in 1944 reported sporozoites in the salivary glands of at least six specimens.

    By means of precipitin tests, the source of blood contained in the stomachs of captured female mosquitoes may be determined. In Peru, A. punctimacula, which is found only in the coastal region, is definitely a human feeder wherever it occurs. The two races of A. pseudopunctipennis, however, differ in this respect. The form which predominates on the eastern slope of the Andes is markedly androphilic, but the coastal variety is much less so.¹⁶⁸

    In a certain malarious coastal village of Peru, the local form of A. pseudopunctipennis has been shown to prefer almost any common domestic animal to man, and the donkey above all others.¹⁶⁹

    Anopheles pseudopunctipennis is, however, the chief vector in Chimbote, Peru.¹⁷⁰ This industrial port, which rose to importance in 1942, was surveyed at that time. Of 472 children between the ages of 5 and 12, 9.1 percent showed parasites in their blood; 24.6 percent had enlarged spleens. Anopheles pseudopunctipennis larvae were abundant in lagoons north and east of the town. Anopheles punctimacula was present but in such small numbers as to be considered of no significance.

¹⁶⁵ Castillo, R. L.. Los vectores de paludismo de los paises de la Costa pacifica de America del Sur y su control. Rev. Kuba 5: 101-105, July-August 1949.
¹⁶⁶ See footnote 28, p.136.
¹⁶⁷ Villalobos, C. E., and Valderrama Delgado, A.: El Anopheles punctimacula en ci Peru. Pub. de la Dir. Gen, de Salubridad, Lima, 1944.
¹⁶⁸ Corradetti, A.: Osservazioni sulle preferenze alimentari dell'Anopheles pseudopunctipennis e dell' Anopheles punctimacula nel Peru. Riv. di parassitol. 9: 129-135, 1948.
¹⁶⁹ Sasse, B. E. and Hackett, L. W. : Note on the Host Preferences of Anopheles pseudopunctipennis . J. Nat. Malaria Soc. 9: 181-182; June 1950.
¹⁷⁰ Westphal, E. A., and Horton, R. K.: Malaria Control Work in Chimbote, Peru. Bol. 0fic. san. panam. 25: 796-809, September 1946.

Other Activities of Antimalaria Organizations

    The malaria survey as well as the malaria control teams in every area were at times hard pressed to keep abreast of seasonal demands. On other occasions, these technically trained units found themselves with leisure time. Several possibilities presented themselves: (1) Where line troops were in the vicinity, to utilize malaria personnel in giving instruction on malaria discipline; and (2) where facilities existed, to expand the training of survey and control personnel so as to include a knowledge of other parasitic and tropical diseases, insect-borne and otherwise, together with the techniques of their prevention and control. The latter procedure was followed somewhat informally in certain cases, on the initiative of the officer in charge, and with the approval of his immediate superior. The development of the modern preventive medicine company, with its broad interest and responsibility for survey, instruction, and control, stemmed from such beginnings.