Francisella tularensis
Patrick Courtney

Francisella tularensis is a small Gram-negative bacillus-shaped aerobic bacterium. It is a highly virulent microbe, with infection possible with as few as ten bacteria present. It is usually inoculated into the skin, but is also capable of being spread via aerosol. Infection with these bacteria causes the disease known as tularemia. F. tularensis was discovered in 1911 after an outbreak killed a large number of ground squirrels around Tulare Lake, California. Later, it was determined to be infectious in humans as well.

F. tularensis primarily infects small mammals, as well as humans, and utilizes many methods of infection. The primary method of human infection is for a vector such as ticks, mites, deer flies, or other arthropods to transfer the bacteria from a rodent to a human. Due to either the bacteria’s infection of rodents or the fact humans around rodents will more likely be infected, tularemia has earned the prestigious nickname “rabbit fever.” Other methods of infection include direct contact with a rodents infected tissue or fluids, ingestion of the bacteria, or inhalation of the bacteria. Inhalation commonly occurs when a lawnmower runs over a dead animal, after which the bacteria are thrown into the air and inhaled by the operator. This has given tularemia its second nickname “lawnmower disease.” Despite its highly infectious nature, no case of human-to-human infection is known to exist.

Once infected, symptoms of fever, chills, aches, joint pain and progressive weakness usually begin to appear within 3-5 days. A vaccine has been developed but is not available to the general public. The preferred antibiotic is Streptomycin. With proper treatment (if needed) fatality is kept down to around 2%.

In the past F. tularensis has been used as a biological anent. During the Battle of Stalingrad in World War II the Soviets unleashed infected rats on the German troops. The infection got so widespread that Field Marshal von Paulus was forced to pause his offensive. Approximately half of the German prisoners captured by the Soviets during the Battle of Stalingrad had symptoms of tularemia.

In the 1950’s the United States began to research ways to weaponize F. tularensis. It developed both an antibiotic resistant lethal agent and an incapacitation agent. Both remain in storage.

F. tularensis is an interesting microbe, partly due to its multiple ways of being spread from to man (bug bite, contact, ingestion, and aerosol inhalation) and the types of hosts in which it can infect.

References

"Francissella tularensis." Wikipedia, the Free Encyclopedia. 24 March 2007, 05:18 UTC. Wikimedia Foundation. 1 Apr. 2007 <http://en.wikipedia.org/wiki/Francisella_tularensis>.

"Key Facts About Tularemia." Center for Disease Control and Prevention. 7 October 2003. 1 Apr. 2007 <http://www.bt.cdc.gov/agent/tularemia/facts.asp>.

"Soviet Army used 'rat weapon' during WWII." Pravda. 2 May 2005. 1 Apr. 2007 <http://english.pravda.ru/main/18/90/363/14923_tularemia.html>.

"Tularemia." Wikipedia, the Free Encyclopedia. 23 March 2007, 03:10 UTC. Wikimedia Foundation. 1 Apr. 2007 <http://en.wikipedia.org/wiki/Tularemia>.

*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.

 

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