Tularemia (rabbit fever, deer fly fever) is infection that is caused by the bacteria Francisella tularensis, which is acquired from wild animals, usually rabbits.
Francisella tularensis is normally present in animals, especially rodents, rabbits, and hares. People may be infected by doing the following:
Francisella tularensis is a potential biological weapon. It can be spread through the air and be inhaled. The size of the airborne particles determines where they lodge in the respiratory tract. Small particles lodge in air sacs of the lungs and cause pneumonia.
Tularemia is not spread from person to person.
Different types of tularemia affect different parts of the body and thus cause different symptoms. Symptoms usually appear 3 to 5 days after exposure to the bacteria but can take up to 14 days.
Sores may develop near the scratch or bite that started the infection. Lymph nodes near the infected area may swell and become painful. A fever up to 104° F (40° C) may appear suddenly, with chills, drenching sweats, and muscle aches. People may have a general feeling of illness (malaise) and feel nauseated. They may vomit and lose weight. A rash may appear at any time. Sometimes pus collects, forming an abscess.
Overall, without treatment, 5 to 15% of people with tularemia die. However, with certain types of tularemia (typhoidal or pneumonic), 30 to 60% die. With appropriate treatment, fewer than 1% die. Death usually results from overwhelming infection, pneumonia, meningitis, or infection of the lining of the abdominal cavity (peritonitis).
Relapses are uncommon but can occur if treatment is inadequate. People who have had tularemia are immune to reinfection.
A doctor suspects tularemia in people who develop sudden fever, swollen lymph nodes, and characteristic sores after having been exposed to ticks or deer flies or after having even slight contact with a wild mammal (especially a rabbit).
Samples of infected material, such as blood, fluids from a lymph node, pus from sores, or sputum, are taken. They are sent to a laboratory where the bacteria can be grown (cultured). Blood may also be tested for antibodies to the bacteria.
If people are visiting areas where tularemia is common, they should do all of the following:
Promptly searching for ticks can help prevent the infection because transmission of infection usually requires that ticks be attached for 4 or more hours. If found, ticks should be removed immediately (see see Sidebar 2: Preventing Tick Bites).
When handling rabbits and rodents, people should wear protective clothing (such as rubber gloves and face masks) because bacteria may be present. Wild birds and game should be thoroughly cooked before they are eaten.
A vaccine is available, but it is given only to people whose occupation puts them at risk, mainly laboratory workers. After exposure to the bacteria (for example, after a laboratory accident), people are given doxycycline or ciprofloxacin to prevent the infection from developing.
People who have tularemia do not need to be isolated. Tularemia is usually treated with injections of gentamicin or streptomycin for 7 to 14 days. Other antibiotics, including fluoroquinolones (such as ciprofloxacin and levofloxacin) and tetracyclines (such as minocycline and doxycycline), are also effective.
Rarely, large abscesses must be drained surgically. Applying warm compresses to an affected eye, wearing dark glasses, and using prescription eye drops may help. People with intense headaches are usually treated with opioids, such as oxycodone.
Last full review/revision September 2008 by Matthew E. Levison, MD