Tularemia is a rare infectious disease that typically attacks the skin, eyes, lymph nodes and lungs. Also called "rabbit fever" or "deer fly fever", it's caused by the bacterium Francisella tularensis.
The disease mainly affects mammals, especially rodents, rabbits and hares, although it can also infect birds, sheep, and domestic animals, such as dogs, cats and hamsters. Tularemia spreads to humans through several routes, including insect bites and direct exposure to an infected animal. Highly contagious and potentially fatal, tularemia usually can be treated effectively with specific antibiotics if diagnosed early.
In the United States, ticks that transmit tularemia to humans include the American dog tick (Dermacentor variabilis), the wood tick (Dermacentor andersoni), and the Lone Star tick (Amblyomma americanum). Deer flies (Chrysops spp.) have also been shown to transmit tularemia in the western United States.
The following ticks are known to transmit Tularemia in humans:
- Lone Star tick (Amblyomma americanum)
- Wood tick (Dermacentor andersoni)
- American Dog tick (Dermacentor variabilis)
Signs + Symptoms
The signs and symptoms of tularemia vary depending on how the bacteria enter the body. Illness ranges from mild to life-threatening. All forms are accompanied by fever, which can be as high as 104 °F. Main forms of this disease are listed below:
- Ulceroglandular: This is the most common form of tularemia and usually occurs following a tick or deer fly bite or after handing of an infected animal. A skin ulcer appears at the site where the bacteria entered the body. The ulcer is accompanied by swelling of regional lymph glands, usually in the armpit or groin.
- Glandular: Similar to ulceroglandular tularemia but without an ulcer. Also generally acquired through the bite of an infected tick or deer fly or from handling sick or dead animals.
- Oculoglandular: This form occurs when the bacteria enter through the eye. This can occur when a person is butchering an infected animal and touches his or her eyes. Symptoms include irritation and inflammation of the eye and swelling of lymph glands in front of the ear.
- Oropharyngeal: This form results from eating or drinking contaminated food or water. Patients with oropharyngeal tularemia may have sore throat, mouth ulcers, tonsillitis, and swelling of lymph glands in the neck.
- Pneumonic: This is the most serious form of tularemia. Symptoms include cough, chest pain, and difficulty breathing. This form results from breathing dusts or aerosols containing the organism. It can also occur when other forms of tularemia (e.g. ulceroglandular) are left untreated and the bacteria spread through the bloodstream to the lungs.
- Typhoidal: This form is characterized by any combination of the general symptoms (without the localizing symptoms of other syndromes).
Tularemia can be difficult to diagnose. It is a rare disease, and the symptoms can be mistaken for other, more common, illnesses. For this reason, it is important to share with your health care provider any likely exposures, such as tick and deer fly bites, or contact with sick or dead animals.
Blood tests and cultures can help confirm the diagnosis. Antibiotics used to treat tularemia include streptomycin, gentamicin, doxycycline, and ciprofloxacin. Treatment usually lasts 10 to 21 days depending on the stage of illness and the medication used. Although symptoms may last for several weeks, most patients completely recover.