Tularemia is a disease cause by the bacterium Francisella tularensis, a Gram-negative coccobacillus that grows slowly in a cultured setting, and only if cysteine and blood or serum are added to the culture media. First identified in 1911 in Tulare County, California, the disease is sometimes referred to as “rabbit fever” or “deerfly fever.”
Tularemia is a widespread zoonotic disease (of lower animals that can be transmitted to humans). The microorganism is indigenous to many species of animals and insects. Humans contract the disease after being bitten by an infected animal or insect, by handling the blood or tissues of infected animals, by inhalation, or by drinking contaminated water. Most cases occur in rural areas among those who come in contact with wild animals or who have encountered ticks, deerflies, or other biting arthropods. Rabbits and rodents are the most common animal sources, but open streams can often become infected by beavers and muskrats. Infected ticks pass the bacterium from the female to the offspring. There is no person to person transmission.
After an incubation period of three to five days, illness produces flu-like symptoms, chest pain, weight loss, and a non-productive cough ultimately, killing an estimated 35% of its victims. The bacterium resists freezing and can remain viable for weeks in water. Streptomycin is the drug of choice, and is more effective than some other broad spectrum antibiotics. Penicillin is not effective. There is a live attenuated vaccine available for those at high risk of exposure, for example, laboratory personnel or anyone who works with animals.