Causes

Tularemia is caused by the bacterium Francisella tularensis.

Humans can get the disease through:

• A bite from an infected tick, horsefly, or mosquito
• Breathing in infected dirt or plant material
• Direct contact, through a break in the skin, with an infected animal or its dead body (most often a rabbit, muskrat, beaver, or squirrel)
• Eating infected meat (rare)

The disorder most commonly occurs in North America and parts of Europe and Asia. Although outbreaks can occur in the United States, they are rare.

Some people may develop pneumonia after breathing in infected dirt or plant material. This is known to occur on Martha's Vineyard, where bacteria are present in rabbits, raccoons, and skunks.

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

The incubation period is 3 to 5 days after exposure. The illness usually starts suddenly, and may continue for several weeks after symptoms begin.

• Chills
• Eye irritation ( conjunctivitis -- if the infection began in the eye)
• Fever
• Headache
• Joint stiffness
• Muscle pains
• Red spot on the skin, growing to become a sore (ulcer)
• Shortness of breath
• Sweating
• Weight loss

Exams and Tests

• Blood culture for tularemia bacteria
• 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 agglutinins and some tests for infectious mononucleosis.

Treatment

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

Tetracycline and chloramphenicol can be used alone, but they have a high relapse rate and 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.

Outlook (Prognosis)

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

Possible Complications

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

When to Contact a Medical Professional

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).

Alternative Names

Deerfly fever; Rabbit fever; Pahvant Valley plague; Ohara disease; Yato-byo (Japan); Lemming fever

References

Penn RL. Francisella tularensis (Tularemia). In: Mandell GL, Bennett JE, Dolin R, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Disease. 7th ed. Philadelphia, Pa: Saunders Elsevier; 2009:chap 227.

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

Update Date: 3/11/2012

Reviewed by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School, Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.