Francisella tularensis and Tularemia
By Andrew Leach

    Tularemia is a very rare disease that is caused by the bacteria Francisella tularensis. It is often referred to as rabbit fever or deerfly fever. Humans most commonly contract this disease by handling or eating undercooked wild animal meat that has been infected by disease carrying ticks. Rabbits are most commonly infected with the disease causing bacteria although muskrats, hares and beavers also have been known to transmit it.
    Outbreaks of tularemia usually occur during hunting season and summer months in which ticks and deerfly are widespread. These insects carry the bacteria to the wild animals, which is how humans can easily become infected with it when in contact with these animals. Infection can also occur by when the skin, eyes, nose or mouth come in contact with the bacteria in anyway. Drinking contaminated water or even breathing dust from contaminated soil can transmit Francisella tularensis.
    Depending upon where in the body infection occurs, symptoms of tularemia can vary greatly. The bacteria can penetrate unbroken skin but infection occurs usually through a scratch or bite. This results in sores that occur where the bacteria infected the skin. Throat infection, vomiting and diarrhea can occur by swallowing the bacteria. Inhaling the bacteria can cause fever and a serious illness very similar to pneumonia.


Tularemia infection caused by Francisella tularensis. Photo from University of Kansas Medical Center

    Symptoms of tularemia usually occur three days after infection with Francisella tularensis but can take up to ten days to appear. Most commonly, after an incubation period of about one week, serious symptoms of high fever, headache and nausea occur. Days later, an inflamed nodule may appear at the site of infection of the bacteria. Lymph glands may become swollen and excrete pus. Following recovery, long-term immunity occurs although reinfection is not unknown.
    Certain antibiotics are effective in treating tularemia. Streptomycin and tetracycline are most commonly used in the treatment of tularemia. The best way to treat Tularemia is to avoid becoming infected with the disease. Appropriate protective gear like rubber gloves and goggles should be worn when skinning wild game.

Francisella tularensis. This bacteria causes Tularemia. Photo from Dennis Kunkel’s Electron Microscopy Image Gallery

    Francisella tularensis contains Gram negative, strict aerobes that are non-motile and can cause human infection. This bacteria requires the amino acid cysteine for growth and development. This makes it easily identified by using cysteine-blood agar in lab testing.

Bibliography
http://www.drkoop.com/conditions/encyclopedia/articles/020000a/020000201.html
http://www.state.hi.us/health/resource/comm_dis/cddtular.htm
http://www.dphhs.state.mt.us/hpsd/pubheal/disease/commdis/tuly.htm
http://www.adam.com/ency/article/00856.htm
http://medic.med.uth.tmc.edu/path/00001501.htm
http://www.pbrc.hawaii.edu/~kunkel/gallery/bacteria/page003/96528a.jpg
http://www.kumc.edu/instruction/medicine/pathology/ed/ch_9b/c9b_tularemia_eschar.html

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