Tularemia is an infectious disease of wild rodents, squirrels, and rabbits. Humans can become infected by having direct contact with an infected animal or from tick, mosquito, or deer fly bites. The disease is caused by the bacterium Francisella tularensis, and is a potentially life-threatening disease.
The various forms of this disease depend on where the bacteria enter the body. Skin contact causes the most common form of the disease. Inhaling the bacteria causes the most deadly form.
This disease can often be treated with antibiotics. Early treatment offers a good outlook for complete recovery. However, even with treatment, some severe cases may be fatal.
Animals carry the bacterium that causes tularemia. The risk of getting the disease grows with frequent animal contact.
Risk factors for the disorder include:
- working closely with animals (veterinarians, zookeepers, park rangers, etc.)
- living in heavily forested areas
- working with animal carcasses (hunters, taxidermists, butchers, etc.)
- gardening and landscaping
The bacterium Francisella tularensis causes this disease. Creatures capable of carrying the bacteria include:
- rabbit and deer ticks
- grizzly bears
- rodents (including hamsters)
- cats (that go outdoors)
The site of entry into the body dictates the form of tularemia. Skin exposure is the most common form. Inhalation through the lungs is the most deadly. However, other forms (if left untreated) can eventually reach the lungs, spinal cord, brain, or heart. This can cause serious complications and sometimes death.
The route of entry and resulting forms include:
- skin exposure causes glandular or ulceroglandular tularemia
- inhalation of aerosolized bacteria causes pneumonic tularemia
- exposure through the eye causes oculoglandular tularemia
- ingestion causes oropharyngeal tularemia
- systemic infection causes typhoidal tularemia
The bacteria’s point of entry determines the symptoms.
Symptoms of ulceroglandular tularemia (infection through the skin) include:
- skin ulcer at the point of contact with the infected animal or at the site of a bite
- swollen lymph nodes near the skin ulcer (most often in the armpit or groin)
Symptoms of glandular tularemia (infection through the skin) are similar to ulceroglandular symptoms but without a skin ulcer.
Symptoms of pneumonic tularemia (the most deadly form of this disease, which is transmitted through inhalation) include:
- chest pain
- breathing difficulty
- high fever
- pneumonia (lung infection)
- muscle pain
Symptoms of oculoglandular tularemia (infection through the eye) may include:
- eye irritation
- eye pain
- eye swelling
- discharge and/or redness of the eye
- a sore on the inside of the eyelid
- swollen lymph glands behind the ear
Symptoms of oropharyngeal tularemia (infection through ingestion of the bacteria) include:
- sore throat
- ulcers in the mouth
- swollen lymph glands in the neck
- tonsillitis (swollen tonsils)
Symptoms of the most rare form of this disease, typhoidal tularemia, include:
- a very high fever
- extreme fatigue
Typhoidal tularemia can lead to pneumonia and an enlarged liver and spleen.
Severe and untreated cases of tularemia may cause chronic heart failure, meningitis (swelling of the membranes that surround your brain and spinal cord), and death.
Diagnosis is not easy, and the various possible routes of entry of the bacterium complicates the issue. Doctors must rely heavily on a patient’s personal and medical history to aid in diagnosis.
Doctors may suspect tularemia if you have had recent travels, insect bites, or animal contact. He or she may also suspect this disease if you already have a serious medical condition that compromises your immune system, such as cancer or HIV/AIDS.
Tests for the presence of this disease include:
- serology test for antibodies your body has created to fight the bacteria
- pleural fluid test (test of fluid from the pleurae in the chest cavity)
- skin biopsy of lesion and microscopic exam (looking for presence of tularemia)
- lymph node biopsy (removal of tissue from a lymph node for examination)
- bone marrow biopsy (removal of a sample of bone marrow for examination)
Each case is treated according to its form and severity. Early diagnosis allows for immediate treatment with antibiotics.
Surgical intervention may be required to drain swollen lymph nodes or to cut away infected tissue from a skin ulcer. You may also be given medications for fever or headache symptoms.
Your prognosis depends upon the severity of the condition and how quickly treatment is started. Delays in diagnosis will cause a worsening of symptoms.
Hospitalization is common in many cases. Death is most common in those with pneumatic tularemia.
According to Medscape Reference, the estimated mortality rate for untreated tularemia is eight percent. However, with early and proper treatment, this number is reduced to less than one percent (Medscape).
Prevention involves taking basic safety precautions. The bacteria thrive in dirty conditions. Outbreaks of this disease have occurred in hunting parties when hunters failed to practice safe cleaning methods and contaminated their belongings.
To safely clean animals when hunting:
- Do not skin or dress (remove the organs of) any animal that appears to be sick.
- Wear gloves and goggles when handling any animal.
- Wash your hands carefully after handling an animal.
- Cook the meat thoroughly.
To decrease your overall risk of contracting this disease:
- Wear long pants and sleeves in the forest for tick prevention.
- Keep animal remains away from food or water.
- Avoid drinking water from lakes or ponds.
- Protect your outdoor pets with flea and tick medicines.
Tularemia is easily aerosolized and can be a potentially deadly bioterrorism agent. Plans for developing a vaccine for tularemia are in progress.