Tularemia

TULAREMIA

Tularemia is a potentially severe and fatal bacterial zoonosis caused by a gram-negative coccobacillus, Francisella tularensis. Tularemia occurs only in the Northern Hemisphere, most commonly in the United States and Europe. In nature, infection occurs mostly in rodents, rabbits, and hares. Humans become infected by handling infectious animal carcasses; eating or drinking contaminated food or water; being bitten by infective ticks, flies, or mosquitoes; or by inhaling contaminated aerosols. The disease is not transmitted person-to-person. The more severe F. tularensis strain A occurs only in the United States and Canada, while the milder strain B occurs throughout the Northern Hemisphere.

Tularemia in humans is relatively rare, and it takes several forms, depending on the route of inoculation. The ulceroglandular form is the most common. It is characterized by an ulcer that develops where infection has penetrated the skin, accompanied by painful swelling of nearby lymph glands. Other forms include the glandular, oculoglandular, oropharyngeal, pneumonic, intestinal, and septic ("typhoidal") types. Following a usual incubation period of three to five days (sometimes longer), all forms have similar acute onsets of fever, headache, musculoskeletal pain, progressive weakness, and weight loss. Patients with tularemia pneumonia typically develop a cough with minimal or no sputum production, chest pain, and difficulty in breathing. Patients with the septic form sometimes develop complications of bleeding, respiratory failure, and shock. All forms can be cured by treatment with antibiotics such as streptomycin, gentamicin, or tetracyclines. The disease can be fatal if not treated early with appropriate antibiotics.

Tularemia is best prevented by avoiding sick or dead animals, protecting against tick and insect bites, and by sanitary practices that protect against contamination of food and water by infected animals.

DAVID T. DENNIS

(SEE ALSO: Vector-Borne Diseases; Zoonoses)

BIBLIOGRAPHY

Beran, G. W. (1994). Handbook of Zoonoses, 2nd edition. Boca Raton, FL: CRC Press.

Dennis, D. T. (1998). "Tularemia." In Maxcy-Rosenau-Last Public Health and Preventive Medicine, 14th edition, ed. R. B. Wallace. Stamford, CT: Appleton & Lange.