Tularemia is a rare infectious disease. Also known as rabbit fever or deer fly fever, it typically attacks the skin, eyes, lymph nodes and lungs. Tularemia is caused by the bacterium Francisella tularensis.
The disease mainly affects rabbits, hares, and rodents, such as muskrats and squirrels. Tularemia can also infect birds, sheep and domestic animals, such as dogs, cats and hamsters.
Tularemia spreads to humans in several ways, including insect bites and direct exposure to an infected animal. Tularemia is highly contagious and potentially fatal, but can usually be treated effectively with specific antibiotics if diagnosed early.
Most people exposed to tularemia who become sick generally do so within three to five days, although it can take as long as 21 days. There are several types of tularemia, 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.
This is the most common form of the disease. Signs and symptoms include:
- A skin ulcer that forms at the site of infection — usually from an insect or animal bite
- Swollen and painful lymph glands
People with glandular tularemia have the same signs and symptoms of ulceroglandular tularemia, but without 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
- Sensitivity to light
This form affects the mouth, throat and digestive tract. Signs and symptoms include:
- Throat pain
- Mouth ulcers
- Abdominal pain
- Inflamed tonsils
- Swollen lymph nodes in the neck
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.
This rare and serious form of the disease usually causes:
- High fever and chills
- Muscle pain
- Sore throat
- Vomiting and diarrhea
- Enlarged spleen
- Enlarged liver
When to see a doctor
If you think you may have been exposed to tularemia, see a doctor as soon as possible. This is especially true if you have been bitten by a tick or have handled a wild animal in an area where tularemia is found and have developed a fever, skin ulcers or swollen glands.
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 in just one way, 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.
Although anyone of any age can develop tularemia, engaging in certain occupations or activities or living in certain areas pose a greater risk.
Living in or visiting certain areas
Tularemia has been reported in the United States, Canada, Mexico, Japan and Europe. In the United States, it's usually more common in Arkansas, Missouri, Oklahoma and South Dakota, though there were outbreaks in Colorado, Nebraska and Wyoming in 2015. Tularemia has also been reported in parts of Massachusetts, including Martha's Vineyard and Nantucket.
Having certain hobbies or occupations
The following can increase your risk of developing tularemia:
- Hunting and trapping. Because hunters are exposed to wild animal blood and may eat wild animal flesh, they're at risk of tularemia.
- Gardening or landscaping. Gardeners and landscapers may also be at risk of tularemia. It's possible that gardeners inhale bacteria that are stirred up while working the soil or when using lawn mowers and weed trimmers.
- Working in wildlife management or veterinary medicine. People who work with wildlife or domestic animals are at increased risk of tularemia.
Left untreated, tularemia can be fatal. Other possible complications include:
- Inflammation of the lungs (pneumonia). Pneumonia can lead to respiratory failure — a condition in which the lungs don't take in enough oxygen, don't release enough carbon dioxide or both.
- Infection around the brain and spinal cord (meningitis). Meningitis is a serious and sometimes life-threatening infection of the fluid and membranes (meninges) surrounding the brain and spinal cord.
- Irritation around the heart (pericarditis). This is swelling and irritation of the thin membrane that surrounds the heart (pericardium).
- Bone infection (osteomyelitis). Tularemia bacteria sometimes spread to the bones.
There's currently no vaccine available for tularemia. 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. Tularemia in the United States is often related to a tick bite. In other parts of the world, tularemia is more commonly contracted through mosquito bites.
If you spend time in tick- or mosquito-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. Use an insect repellent with 20% to 30% DEET, picaridin or IR3535, but follow the manufacturer's directions carefully. Apply insect repellent in moderation, and wash it off at the end of the day.
Check yourself for ticks often and remove them immediately if you find any. Be sure to check your pets too.
- 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.
- Don't eat undercooked meat. Cook all wild meat thoroughly, and avoid skinning or dressing any animal that appeared ill. Heat kills F. tularensis, so cook meat to the right temperature — a minimum of 160 F (71.1 C) for ground meat and game meat — to make it safe to eat. Poultry should be cooked to 165 F (73.8 C).
- 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 flea and tick protection, and don't let them come in close contact with wild or dead animals.