Tularemia

Definition

Tularemia is an infection common in wild rodents. It is transmitted to humans by contact with infected animal tissues or by ticks, biting flies, and mosquitoes.

Alternative Names

Deerfly fever; Rabbit fever; Pahvant Valley plague; Ohara disease; Yatobyo (Japan); Lemming fever

Causes, incidence, and risk factors

Tularemia is caused by the bacterium Francisella tularensis.

Humans can get the disease through:

• Direct contact, through a break in the skin, with an infected animal or its dead body
• The bite of an infected tick, horsefly, or mosquito
• Eating infected meat (rare)

Areas where the disorder most commonly occurs include North America and parts of Europe and Asia. The illness may continue for several weeks after symptoms begin.

Some people may develop pneumonia after being infected. Risk factors include recent exposure to rabbits or a recent tick bite. The disease is very rare in the United States.

Francisella tularensis is considered a potential bioterrorism agent. An aerosol release would be a possible method of infection. Pneumonia cases would start 1 - 10 days after people were exposed.

Symptoms

• Chills
• Fever
• Headache
• Joint stiffness
• Muscle pains
• Possible conjunctivitis
• Red spot on the skin, enlarging to a sore (ulcer)
• Shortness of breath
• Sweating
• Weight loss

Signs and tests

• Blood culture for tularemia
• Blood test measuring the body's immune response to the infection (serology for tularemia)
• Chest x-ray
• Polymerase chain reaction (PCR) test of a sample from an ulcer

This disease may also affect the results of febrile/cold agglutinins.

Treatment

The goal of treatment is to cure the infection with antibiotics. Streptomycin and tetracycline are commonly used to treat this infection. Once daily gentamycin treatment has been tried with excellent results as an alternative therapy to streptomycin. However, only a few cases have been studied to date.

Tetracycline and Chloramphenicol can be used alone, but they are not considered a first-line treatment.

Note: oral tetracycline is usually not prescribed for children until after all their permanent teeth have come in. It can permanently discolor teeth that are still forming.

Expectations (prognosis)

Tularemia is fatal in about 5% of untreated cases, and in less than 1% of treated cases.

Complications

• Bone infection (osteomyelitis)
• Infection of the sac around the heart (pericarditis)
• Meningitis
• Pneumonia

Calling your health care provider

Call your health care provider if symptoms develop after a rodent bite, tick bite, or exposure to the flesh of a wild animal.

Prevention

A vaccine is recommended for people at high risk (trappers, hunters, and laboratory workers who work with the bacteria).

References

Schaffner W. Tularemia and other Francisella infections. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 332.

Cronquist SD. Tularemia: the disease and the weapon. Dermatol Clin. 2004; 22(3): 313-20, vi-vii.