Tularemia

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at July 29, 2016
StartDiseasesTularemia

Tularemia is a rare infectious disease that is also known as rabbit fever or deerfly fever. It mainly affects mammals but can also infect birds. It can spread to humans through insect bites and exposure to an infected animal. 

Contents

Definition & Facts

Tularemia is caused by a bacteria called Francisella tularensis. It particularly affects rodents, rabbits and hares. However, it can also infect birds, sheep, and other domesticated animals. Tularemia has occurred in all of the states of the union except Hawaii. However, it is most common in the south central United States, the Pacific Northwest, and parts of Massachusetts.

Tularemia is so rare that it was removed from the reportable disease list in 1995. Still, there have been cases reported worldwide. Tularemia can be classified into two main groups: the common ulceroglandular form and the more lethal typhoidal form. Some divide the disease into seven forms. 

Symptoms & Complaints

The symptoms of tularemia vary, depending on where the bacteria enter the body. Ulcerograndular tularemia enters through the skin (percutaneous transmission). Its symptoms include:

Glandular tularemia is a form of the illness that also infects the skin. The symptoms are similar to ulceroglandular symptoms, but there is no skin lesion.

Pneumonic tularemia is the most lethal form of the illness. It is transmitted through inhalation. Its symptoms can include:

Oculoglandular tularemia is a type of infection that enters through the eye. Its symptoms include:

Oropharyngeal tularemia comes through ingestion of the bacteria. Its symptoms can include:

Typhoidal tularemia is very rare. Its symptoms can include:

  • High fever
  • Extreme fatigue
  • Diarrhea
  • Vomiting

Severe or untreated cases of tularemia can cause:

Causes

The animals that can carry tularemia include rabbit and deer ticks, deer flies, grizzly bears, hares, rabbits, rodents, and domesticated cats that go outdoors. The type of tularemia that a person develops will depend on how the bacteria enters the body.

Exposure through the skin is the most common form of the illness. When the illness is not treated, some forms of the illness will eventually affect the lungs, spinal cord, brain, and heart.

The illness doesn't occur naturally in humans and doesn't pass from person to person. It occurs mostly in rural areas where there are many animals to be found. The bacteria can survive for a long time in soil, water, and dead animals.

Although it is uncommon, it's possible to get tularemia as a foodborne illness from eating the undercooked meat of an infected animal or drinking contaminated water. This kind of exposure is the cause of oropharyngeal tularemia. Heat will kill off the bacteria, so it is important to cook meat at the right temperature. A minimum of 165 F (73.8 C) is enough to make the meat safe to eat.

In the United States, people who live in or visit areas of Arkansas, Missouri, and Oklahoma, may be at greater risk for contracting the illness because of the high concentration of ticks in those areas. People who work in wildlife management or veterinary medicine are at increased risk as well.

Diagnosis & Tests

Tularemia is difficult to diagnose. It is a rare disease, and its symptoms can be mistaken for many other illnesses. Consequently, it is always important for a patient to share possible sources of exposure with their doctor. Blood tests and cultures can help with the diagnosis. 

Treatment & Therapy

Streptomycin is considered to be the drug of choice in combating tularemia. Less data is available for other drugs. Tetracycline is considered to be useful, but relapse rates of up to 50% have been reported in patients who are treated with the drug.

The bacteria which causes the illness are resistant to penicillin. The doctor will also need to treat any complications that come along with the illness, such as meningitis or pneumonia. Generally speaking, patients develop immunity to tularemia after recovering from it. However, some people may have a recurrence or reinfection. 

Prevention & Prophylaxis

There is no currently available vaccine for tularemia. The most that a person can do to prevent the illness is to use the following measures to prevent exposure:

  • Guard against insects - People most often get the illness from tick bites. It is wise to wear long sleeves and long pants when going into an area that has a lot of insects in it. Care should be taken to tuck the pants into the socks. A hat should also be worn. After spending any period of time in such an area, it is important to check for bugs on the body. An insect repellant should also be used. 
  • Gardening - Since a gardener has a lot of contact with the soil, a face mask should be worn. 
  • Handling animals - Someone who handles wild animals should take care to wear gloves and protective goggles. Also, the hands should be washed thoroughly after the animals are handled. If one goes hunting, then all of the meat should be cooked thoroughly.
  • Pets - Pets can contract the disease if they eat a diseased animal or are bitten by an infected tick. Animals should not be allowed to roam without any supervision and should be given flea and tick protection. If the pet must be let outside unsupervised, then a person should always be on the watch for symptoms of tularemia.