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Tularemia

by Matthew E. Levison, MD

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.

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 permethrin

  • 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 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.

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 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.

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Drugs Mentioned In This Article

  • Generic Name
    Select Brand Names
  • ELIMITE, NIX
  • CILOXAN, CIPRO
  • PERIOSTAT, VIBRAMYCIN
  • IQUIX, LEVAQUIN, QUIXIN
  • No US brand name
  • GENOPTIC
  • MINOCIN
  • OXYCONTIN