Tularemia is a disease that humans typically acquire after skin or mucous membrane contact with tissues or body fluids of animals infected with tularensis or from bites of infected ticks, deerflies or mosquitoes. Less commonly, inhalation of contaminated dusts or ingestion of contaminated foods or water may produce clinical disease. Respiratory exposure by aerosol typically causes typhoidal or pneumonic tularemia.
The germs can remain alive for weeks in water, soil, carcasses, hides, and for years in frozen rabbit meat. It is resistant for months to temperatures of freezing and below. It is easily killed by heat and disinfectants.
A clue to the diagnosis of tularemia subsequent to a biological warfare attack with F. tularensis could be a large number of patients presenting with similar systemic illnesses and a non-productive pneumonia in an area around the same time.
- The clinical presentation of tularemia may be severe, yet non-specific
- X-rays show pneumonia or enlarged glands in the chest in typhoidal disease. In general, chest radiographs show that approximately 50% of patients have pneumonia
- Laboratory tests are not very helpful
- Tularemia can be diagnosed by recovery of the germ by cultures from blood, ulcers, eyes or sputum, even if the patient has been treated
After an incubation period varying from one to 21 days (average three to five days), onset is usually acute. Tularemia typically appears in one of several forms in humans, depending upon the route of inoculation:
Consisting of 75–85% of the cases, this type is most often acquired through infection of the skin or mucous membranes with blood or tissue fluids of infected animals. It is characterized by fever, chills, headache, malaise, an ulcerated skin lesion and painful glands. The skin lesion is usually located on the fingers or hand where contact occurs.
Consisting of 5–15% of naturally acquired cases, this type occurs mainly after inhalation of germs. The germs would presumably be most likely delivered by aerosol in a biological warfare attack and would primarily cause this form of tularemia. It causes fever, prostration and weight loss. Pneumonia may be severe, and it is most common in typhoidal tularemia (80% of cases). Respiratory symptoms, chest pain and a cough may also be present. About 35% of untreated naturally acquired typhoidal cases die.
Consisting of 5–10% of cases, this type results in fever and tender glands but no skin ulcer.
Since there is no known human-to-human transmission, neither isolation nor quarantine are required; standard precautions are appropriate for care of patients with draining lesions or pneumonia. Appropriate therapy includes one of the following antibiotics: