Tularemia is a rare infectious disease that can attack the skin, eyes and lungs. Fewer than 200 cases of tularemia are reported annually in the United States — mainly in western and south-central states.
Tularemia, often called rabbit fever or deerfly fever, is caused by the bacterium Francisella tularensis. The disease mainly affects mammals, especially rodents, rabbits and hares, though it can also infect birds, reptiles and fish.
Tularemia spreads to humans through several routes, including insect bites and direct exposure to an infected animal. Highly contagious and potentially fatal if not treated, tularemia has been identified as a possible bioweapon. If diagnosed early, doctors can usually treat tularemia effectively with antibiotics.
Most people exposed to tularemia become sick within two to 10 days. Several types of tularemia exist, each with its own set of symptoms.
This is by far 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
People with glandular tularemia have:
- The same signs and symptoms of ulceroglandular tularemia, except no skin ulcers
This form affects the eyes, and may cause:
- Eye pain
- Eye redness
- Eye swelling and discharge
- An ulcer on the inside of the eyelid
This causes signs and symptoms typical of pneumonia:
- Chest pain
- Difficulty breathing
Other forms of tularemia also can spread to the lungs.
This rare and serious form of the disease usually causes:
- Extreme exhaustion
- Weight loss
It can also affect a number of body organs, including the lungs
Doctors may check for F. tularensis in a blood or sputum sample that’s cultured to encourage the growth of the bacteria. But the preferred way to diagnose tularemia is usually to identify antibodies to the bacteria in a sample of blood. You’re also likely to have a chest X-ray to look for signs of pneumonia.
Tularemia doesn’t occur naturally in humans, but it does in animals. Worldwide, more than 200 species of mammals, as well as birds, insects and fish, may be infected with F. tularensis. The bacteria can live for an extended time in animals, and even insects can act as reservoirs for disease. 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 deerflies are most likely to transmit the disease to humans. Tick bites cause a large number 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 the 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 well-cooked meat — at least 160 F (71C) — is usually safe to eat.
Tularemia: Where, when and how much
- Where. Tularemia occurs worldwide — especially in rural areas in eastern Europe, China and Japan. In the United States, most cases are clustered in the rural western and in south-central states, such as Arkansas, Missouri and Oklahoma.
- When. Tick season (generally June through September) and hunting season are prime times for infection.
- How much. Tularemia is highly contagious. Inhaling as few as 10 to 50 bacteria can cause disease. Yet tularemia is rare, with only about 200 cases reported each year. The bacteria are transmitted from animals to humans, not from person to person.
Tularemia can be effectively treated with antibiotics such as streptomycin or gentamicin, which are given by injection directly into a muscle or vein. Depending on the type of tularemia being treated, doctors may prescribe oral antibiotics such as tetracycline instead. You’ll also receive therapy for any complications such as meningitis or pneumonia. In general, you should be immune to tularemia after recovering from the disease, but some people may experience a recurrence or reinfection.
If you work in a high-risk occupation or live in an area where tularemia is present, these measures may help reduce your chance of infection:
- Protect yourself from insects. Most people get tularemia though tick bites. If you spend time in tick-infested areas, wear long-sleeved shirts and long pants, tuck your pants into your socks, and use a broad-brimmed hat to help protect your face and neck. Even bundled up, you’ll need to check your skin and clothing often for ticks. Use an insect repellant, but follow the manufacturer’s directions carefully. Products containing DEET are still considered the most effective against ticks, although oil of lemon eucalyptus or natural insecticides may offer some protection. Use the lowest concentration of repellant for the circumstances, apply it in moderation, and wash it off at the end of the day. Don’t use repellants containing DEET on infants younger than 2 months.
- Take care when gardening. Home gardeners and professional landscapers should consider wearing a face mask when excavating the soil, clearing weeds or brush, or mowing lawns.
- Handle animals carefully. If you hunt or handle wild rabbits or hares, wear gloves and protective goggles, and wash your hands thoroughly with soap and hot water after touching the animal. Cook all wild meat thoroughly, and avoid skinning or dressing any animal that appeared ill.
- Protect your pets. Livestock and pets can contract tularemia if they eat part of a diseased rabbit or are bitten by an infected tick. To help keep your pets safe, avoid letting them outside unsupervised, provide them with a flea and tick collar, and don’t let them come in close contact with wild or dead animals.