Tularemia (rabbit fever, deer fly fever) is infection caused by the gram-negative bacterium Francisella tularensis that is contracted from wildlife, usually rabbits.

People become infected with Francisella tularensis mainly by eating or touching infected animals. Hunters, butchers, farmers, fur handlers, and laboratory workers are most commonly infected. In the winter, most infections result from contact with wild rabbits (especially while skinning them). In the summer, infection usually results from being bitten by infected ticks or deer flies. Rarely, tularemia may be caused by eating undercooked meat or drinking contaminated water, or by inhaling bacteria that have become airborne (as occurs during butchering, or may occur while mowing if an infected animal is run over). The bacterium can penetrate unbroken skin. Person-to-person transmission has not been reported.

Types of Tularemia There are four types of tularemia. In the most common type (ulceroglandular type), sores develop on the hands and fingers, and the lymph nodes swell on the same side as the infection. The second type (oculoglandular type) involves the eye, causing redness and swelling along with swollen lymph nodes; this type probably results from touching the eye with a contaminated or infected finger, or from having infected fluid splashed into the eye. In the third type (glandular type), lymph nodes swell but no sores develop, suggesting that the source is ingested bacteria. The fourth type (typhoidal type) leads to a high fever, abdominal pain, and exhaustion. If the bacteria that cause tularemia are inhaled, pneumonia can result.

Symptoms

The symptoms start suddenly 1 to 10 days—usually 2 to 4 days—after contact with the bacterium. Initial symptoms include headaches, chills, nausea, vomiting, a fever of up to 104° F, and severe exhaustion. Extreme weakness, recurring chills, and profuse drenching sweats develop. In 24 to 48 hours, an inflamed blister appears at the infection site—usually the finger, arm, eye, or roof of the mouth—except in the glandular and typhoidal types of tularemia. The blister rapidly fills with pus and opens to form a sore. Single sores commonly appear on the arms or legs, but many sores usually appear in the mouth or eye. Lymph nodes around the sore enlarge and may produce pus, which later drains. A rash may appear at any time during the course of the disease.

Pneumonia sometimes develops, although the pneumonia may cause only mild symptoms, such as a dry cough that causes a burning sensation in the middle of the chest. Other people with pneumonia become delirious.

Diagnosis and Treatment

A doctor suspects tularemia in a person who develops sudden fever, swollen lymph nodes, and characteristic sores after having been exposed to ticks or deer flies or after having had even slight contact with a wild mammal (especially a rabbit). Infections acquired by laboratory workers frequently affect only the lymph nodes or lungs and are difficult to diagnose. The bacteria may be grown on special laboratory cultures.

Tularemia is treated with injections of streptomycin for 7 to 14 days. Moist bandages are placed on the sores and changed frequently. These bandages help prevent the spread of infection. Rarely, large abscesses (collections of pus) need to be drained by surgical incision. Applying warm compresses to an affected eye and wearing dark glasses may give some relief. People with intense headaches are usually treated with opioid pain relievers, such as codeine.

About one third of untreated people die, but people who are treated almost always survive. Death usually results from overwhelming infection, pneumonia, infection of the tissues covering the brain and spinal cord (meningitis), or infection of the lining of the abdominal cavity (peritonitis). Relapses are uncommon but can occur if treatment is inadequate. A person who has had tularemia develops immunity to reinfection.

Last full review/revision February 2003