Rabbit Fever, Deer Tick Fever
What is Tularemia?
Tularemia is a bacterial infection that is caused by transmission from wild animals to humans, by direct contact with infected animal tissues, or by an intermediary insect such as a tick; in the US, wild cottontail rabbits are the main source of the disease. Infection in humans can occur through the skin, lungs, or intestinal tract. It can result in a widespread, life-threatening disease, or be completely without symptoms. Infection will develop within a week of exposure to the bacteria. The disease does not spread from human to human.
How is it diagnosed?
History includes exposure to wild animals or ticks in areas where the disease is known to exist; at-risk occupations include hunters, butchers, and rabbit keepers.
Symptoms of tularemia include rapid onset of a high fever, headache, nausea and weakness. In most cases a red, itchy skin lesion develops at the site of infection and then quickly ulcerates. Swollen and painful lymph nodes may be reported. Difficulty breathing, productive cough, and chest pain may be symptoms if tularemia involves the lungs. Less commonly there may be abdominal pain and diarrhea.
Physical exam may reveal a nonspecific rash on the trunk or extremities, fever of 104° F to 106° F, and an enlarged spleen. Listening to the chest might reveal signs of pneumonia. There may be signs of other organs being affected, including the heart, brain, and bones.
Tests: A blood test (serum agglutinins) will be positive after the second week of illness, and may stay positive for years. The bacterium can be cultured from a skin ulcer or infected lymph node, confirming the diagnosis.
How is it treated?
Tularemia is treated with antibiotics until four to five days after the fever subsides. Treatment of pneumonia is supportive in nature. In severe cases, corticosteroids may be used to reduce inflammation.
What might complicate it?
The infection can result in pneumonia, pericarditis, meningitis, or osteomyelitis, due to spread through the blood. If another medical condition is present that involves depressed immunity, tularemia will present as a more serious disease.
The prognosis for tularemia is good with rapid diagnosis and antibiotic treatment, resulting in full recovery. If the infection is left untreated, prognosis worsens and can become grave, especially in immunocompromised individuals.
Tularemia needs to be distinguished from infections such as pyoderma, cat-scratch disease, brucellosis, plague, anthrax, infectious mononucleosis, and other bacterial and fungal diseases that invade the lungs, gastrointestinal tract, and skin.
Infectious disease specialist, pulmonary disease specialist and dermatologist.
Last updated 19 December 2011