Malaria has been a cause for considerable concern throughout the history of man. With probable origination in Africa, malarial parasites from fossils of mosquitoes have been dated back to 30 million year ago. These unique protozoal parasites and causative agents of malaria belong to the Plasmodium genus consisting of four species of obligate intracellular sporozoans: P. malariae, P. vivax, P. ovale, and P. falciparum. With the exception of P. malariae, the plasmodium species are exclusive parasites of humans. At present, nearly 300 million people are affected by malaria globally, and about I to 1.5 million infected die from the disease per year.
Of the four species, Plasmodium falciparum is the predominant species with about 120 million new cases and one million deaths per year globally. The fight against Plasmodium falciparum species has proven to be formidable with an increasing rise in drug resistant strains being isolated in Asia.
The life cycle of the P. falciparum and other plasmodium species occurs in two distinct phases: a sexual phase within a vertebrate host and an asexual phase within an insect vector. The female Anopheles mosquito is always the vector while humans are the primary hosts. Only 60 out of 380 known species of the Anopheles mosquito transmit malaria. The asexual stage occurs as the mosquito injects her saliva into the host bloodstream containing spindle-shaped cells called sporozoites which then proceed to the liver to divide. Schizogony, or the asexual division of sporozoites, proceeds much more rapidly with P. falciparum than any other plasmodium species. Sporogony, or sexual division, occurs within the mosquito's stomach as it draws infected blood from its host and fertilizes the macrogametes within the blood. The life cycle of the P. falciparum is illustrated on the following page
The incubation period for malaria varies between 10 to 16 days, and initial infection can be detected by the formation of ring trophozoites within RBC'S. General symptoms include fatigue, nausea, fever, and chills. Malaria caused by the falciparum species is the most severe in nature characterized by persistent fever, rapid pulse, cough, and weakness, and also has the highest mortality rate.
The most common treatment against malaria is the use of an extract from the cinchona tree to synthesize the drug called quinine. Nonresistant strains are suppressed by chloroquine while resistant strains of P. falciparum require a stronger dose of quinine.
Due to the widespread prevalence of malaria, considerable research has been devoted to studying the microbiology and biology of the plasmodium species in the eventual hope of acquiring a vaccine for the disease.
*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.
Return to Missouri S&T Microbiology HomePage Go to DJW's HomePage
This Document is maintained by djwesten@ mst.edu
