Tularemia (rabbit fever, deer fly fever) is infection that is caused by the bacteria Francisella tularensis, which is acquired from wild animals, usually rabbits.

• Handling carcasses, being bitten by a tick, inhaling infected sprayed particles, and eating or drinking infected material can cause infection.
• Symptoms can include fever, sores, and swollen lymph nodes.
• Cultures of tissue samples or blood help doctors make the diagnosis.
• Injections of antibiotics are almost always effective.
• Preventing tick bites, handling carcasses carefully, and disinfecting water can reduce the risk of tularemia.

Francisella tularensis is normally present in animals, especially rodents, rabbits, and hares. People may be infected by doing the following:

• Handling infected animal carcasses (as when hunters skin rabbits or when butchers, farmers, fur handlers, and laboratory workers handle animals or animal products)
• Being bitten by an infected tick, deerfly, or other insect, usually during the summer (particularly for children)
• Eating or drinking contaminated food (such as undercooked rabbit meat) or water
• Inhaling airborne particles that contain the bacteria (as when grass is mowed or brush is cut or when people are working with the bacteria in a laboratory)

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.

Types of Tularemia
There are several types of tularemia. Ulceroglandular: This type is the most common. Open painful sores develop where the bacteria entered the skin: through a break in the skin, usually on the hands and fingers, or a tick bite, usually in the groin, armpit, or trunk. The bacteria travel to nearby lymph nodes, making them swollen and painful. Occasionally, the skin around the lymph nodes breaks down, and pus may drain from them. Glandular: The lymph nodes become swollen and painful, but sores do not form. Oculoglandular: An eye becomes painful, swollen, and red, and pus often oozes from it. Nearby lymph nodes become swollen and painful. This type probably results from touching the eye with a contaminated finger or from having infected fluid splashed into the eye. Oropharyngeal: The throat (pharynx) is sore, and lymph nodes in the neck are swollen. Some people also have abdominal pain, nausea, vomiting, and diarrhea. This type is usually caused by eating undercooked contaminated meat. Typhoidal: Chills, high fever, and abdominal pain develop, but no sores form and lymph nodes do not swell. This type develops when the bloodstream is infected. Sometimes the source of infection is unknown. Pneumonic: The lungs are infected. People may have a dry cough, be short of breath, and have chest pain. This type is caused by inhaling the bacteria or spread of the bacteria through the bloodstream to the lungs. This type develops in 10 to 15% of people with ulceroglandular tularemia and in 50% of people with typhoidal tularemia.

Symptoms

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.

Diagnosis

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.

Prevention

If people are visiting areas where tularemia is common, they should do all of the following:

• Apply insect repellent containing 25 to 30% diethyltoluamide (DEET) to exposed skin
• Wear clothing treated with a repellent containing permethrinSome Trade Names
  NIX
  
• Stay on paths and trails when walking in wooded areas
• Walk in the center of trails to avoid brushing against bushes and weeds
• Wear long pants and tuck them into socks and boots
• Thoroughly search their clothing, themselves, family members, and pets for ticks
• Not drink or bathe, swim or work in untreated water, which may be contaminated

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 Bacterial Infections: 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 doxycyclineSome Trade Names
VIBRAMYCIN
or ciprofloxacinSome Trade Names
CILOXAN CIPRO
to prevent the infection from developing.

Treatment

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 ciprofloxacinSome Trade Names
CILOXAN CIPRO
and levofloxacinSome Trade Names
LEVAQUIN QUIXIN
) and tetracyclines (such as minocyclineSome Trade Names
MINOCIN
and doxycyclineSome Trade Names
VIBRAMYCIN
), 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 oxycodoneSome Trade Names
OXYCONTIN
.

Last full review/revision September 2008 by Matthew E. Levison, MD