Tularemia

DEFINITION

Tularemia is a rare infectious disease that typically attacks the skin, eyes, lymph nodes and lungs. Tularemia — also called rabbit fever or deer fly fever — is 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.

CAUSES

Tularemia doesn’t occur naturally in humans and isn’t known to pass from person to person. However, tularemia occurs worldwide, especially in rural areas, because many mammals, birds and insects are infected with F. tularensis. The organism can live for weeks in soil, water and dead animals.

Unlike some infectious diseases that spread from animals to people through a single route, tularemia has several modes of transmission. How you get the disease usually determines the type and severity of symptoms. In general, you can get tularemia through:

• Insect bites. Although a number of insects carry tularemia, ticks and deer flies are most likely to transmit the disease to humans. Tick bites cause a large percentage of cases of ulceroglandular tularemia.
• Exposure to sick or dead animals. Ulceroglandular tularemia can also result from handling or being bitten by an infected animal, most often a rabbit or hare. Bacteria enter the skin through small cuts and abrasions or a bite, and an ulcer forms at the wound site. The ocular form of tularemia can occur when you rub your eyes after touching an infected animal.
• Airborne bacteria. Bacteria in the soil can become airborne during gardening, construction or other activities that disturb the earth. Inhaling the bacteria can lead to pneumonic tularemia. Laboratory workers who work with tularemia also are at risk of airborne infection.
• Contaminated food or water. Although uncommon, it’s possible to get tularemia from eating undercooked meat of an infected animal or drinking contaminated water. The signs include vomiting, diarrhea and other digestive problems (oropharyngeal tularemia).

Heat kills F. tularensis, so cook meat to the right temperature — a minimum of 165 F (73.8 C) for ground meat and game meat — to make it safe to eat.

SYMPTOMS

Most people exposed to tularemia who become sick generally do so within three to five days, although it can take as long as 14 days. Several types of tularemia exist, and which type you get depends on how and where the bacteria enter the body. Each type of tularemia has its own set of symptoms.

Ulceroglandular tularemia

This is the most common form of the disease. Signs and symptoms include:

• A skin ulcer that forms at the site of infection — usually an insect or animal bite
• Swollen and painful lymph glands
• Fever
• Chills
• Headache
• Exhaustion

Glandular tularemia

People with glandular tularemia have the same signs and symptoms of ulceroglandular tularemia, but without skin ulcers.

Oculoglandular tularemia

This form affects the eyes and may cause:

• Eye pain
• Eye redness
• Eye swelling and discharge
• An ulcer on the inside of the eyelid
• Sensitivity to light

Oropharyngeal tularemia

Usually caused by eating poorly cooked wild animal meat or drinking contaminated water, this form affects the mouth, throat and digestive tract. Signs and symptoms include:

• Fever
• Throat pain
• Mouth ulcers
• Vomiting
• Diarrhea
• Inflamed tonsils
• Swollen lymph nodes in the neck

Pneumonic tularemia

This type of tularemia causes signs and symptoms typical of pneumonia:

• Dry cough
• Chest pain
• Difficulty breathing
• Other forms of tularemia also can spread to the lungs.

Typhoidal tularemia

This rare and serious form of the disease usually causes:

• High fever
• Extreme exhaustion
• Vomiting and diarrhea
• Enlarged spleen (splenomegaly)
• Enlarged liver (hepatomegaly)
• Pneumonia

When to see a doctor

If you think you may have been exposed to tularemia — especially if you’ve been bitten by a tick or handled a wild animal in an area where tularemia is found and have developed fever, skin ulcers or swollen glands — see a doctor as soon as possible.