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.
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.
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
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
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:
- Throat pain
- Mouth ulcers
- 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
- Extreme exhaustion
- Vomiting and diarrhea
- Enlarged spleen (splenomegaly)
- Enlarged liver (hepatomegaly)
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.
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.
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 most common in the south-central states, the Pacific Northwest and parts of Massachusetts, including Martha's Vineyard.
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 their 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 mowers and weed trimmers.
- Working in wildlife management or veterinary medicine. People who work with wildlife 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 pericardium, the thin membrane that surrounds the heart. Mild pericarditis may improve without treatment, but more-serious cases may require antibiotic therapy.
- Bone infection (osteomyelitis). Tularemia bacteria sometimes spread to the bones.
There's currently no publicly available vaccine 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. Most people in the United States get tularemia through tick bites. In other parts of the world, tularemia is most 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. Even bundled up, you'll need to check your skin and clothing often for ticks.
Use an insect repellent with 20 to 30 percent DEET, picaridin or IR3535, but follow the manufacturer's directions carefully. Apply insect repellant 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.
- 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 flea and tick protection, and don't let them come in close contact with wild or dead animals.
Because it's rare and because it shares symptoms with other diseases, tularemia may be difficult to diagnose. Doctors may check for F. tularensis in a blood or sputum sample that's cultured to encourage the growth of the bacteria.
Sometimes tularemia can be identified by antibodies to the bacteria in a sample of blood, but these only develop several weeks after infection. You're also likely to have a chest X-ray to look for signs of pneumonia.
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 doxycycline (Oracea, Vibramycin, others) 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.
Preparing for an appointment
You're likely to start by seeing your primary care doctor. However, in some cases when you call to set up an appointment, you may be referred immediately to an infectious diseases specialist.
Here's information to help you prepare for your appointment.
What you can do
- List your symptoms, including any that may seem unrelated to the reason for which you scheduled the appointment.
- Write down key personal information, especially recent activities, such as hunting or gardening or traveling to tick-infested areas.
- Take a list of all medications, vitamins or supplements you're taking.
- Write down questions to ask your doctor.
Preparing a list of questions for your doctor will help you make the most of your time together. List your questions from most important to least important. For tularemia, some basic questions to ask your doctor include:
- What's the most likely cause of my symptoms?
- Are there other possible causes for my symptoms?
- What tests do I need?
- What treatments are available? And, what side effects can I expect?
- I have other health conditions. How can I best manage these conditions together?
- Are there brochures or other printed material I can take with me? What websites do you recommend?
Don't hesitate to ask any other questions you may have.
What to expect from your doctor
Your doctor is likely to ask you a number of questions, including:
- When did you begin experiencing symptoms?
- Have you been hunting, gardening or traveling to tick-heavy areas recently?
- Have your symptoms been continuous or do they come and go?
- How severe are your symptoms?
- Does anything improve your symptoms?
- Is there anything that makes your symptoms worse?