Tularemia

Other Names: Francisella tularensis infection; Deerfly fever; Rabbit fever; Pahvant Valley plague; Ohara disease; Yatobyo (Japan); Lemming fever

Tularemia is an infection caused by the bacterium Francisella tularensis. It is more common in rodents and rabbits but has been found in other animals including domestic cats, sheep, birds, and hamsters.

Transmission

Humans can become infected in several different ways: by handling infected animals, through tick or deer fly bites, by drinking contaminated water, or by inhaling contaminated dust or aerosols. Person-to-person transmission has not been reported.

Types

The type of tularemia and the particular signs and symptoms vary depending on how the bacteria enter the body.

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 orophyangeal 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)

Symptoms

The symptoms of tularemia usually appear 3 to 5 days after exposure, but can take as long as 14 days to appear. Symptoms may include:

• Fever
• Chills
• Headache
• Diarrhea
• Muscle pains
• Abdominal pain
• Vomiting
• Joint pain
• Dry cough
• Fatigue
• Skin rash
• Progressive weakness

Symptoms vary depending on the way the bacteria enter the body. Additional signs and symptoms may include pneumonia, ulcers on the skin or mouth, swollen eyes, and a sore throat.

Diagnosis

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.

The laboratorial isolation of F. tularensis requires special media such as buffered charcoal yeast extract agar. It cannot be isolated in the routine culture media because of the need for sulfhydryl group donors (such as cysteine). The microbiologist must be informed when tularemia is suspected not only to include the special media for appropriate isolation, but also to ensure that safety precautions are taken to avoid contamination of laboratory personnel.

Serological tests (detection of antibodies in the serum of the patients) are available and widely used. Cross reactivity with Brucella can confuse interpretation of the results, so diagnosis should not rely only on serology. Molecular methods such as PCR are available in reference laboratories.

Treatment

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.

Prognosis

Since the invention of antibiotics, the rate of death associated with tularemia has decreased from 60% to less than 4%.

Epidemiology

Tularemia is most common in the Northern Hemisphere, including North America and parts of Europe and Asia. It occurs between 30º and 71º north latitude. About 1.86 cases per 100,000 persons occur each year with higher rates in those between 55 and 70.

Prevention

• Use Environmental Protection Agency (EPA)-registered insect repellentsexternal icon containing DEET, picaridin, IR3535, Oil of Lemon Eucalyptus (OLE), para-menthane-diol (PMD), or 2-undecanone. EPA’s helpful search toolexternal icon can help you find the product that best suits your needs. Always follow product instructions.
• Wear long pants, long sleeves, and long socks to keep ticks and deer flies off your skin.
• Remove attached ticks promptly with fine-tipped tweezers.
• Don’t drink untreated surface water.
• Don’t mow over sick or dead animals. When possible, check the area for carcasses prior to mowing.
• Use of masks during mowing and other landscaping activities may reduce your risk of inhaling the bacteria, but this has not been studied.
• Use gloves when handling animals, especially rabbits, muskrats, prairie dogs, and other rodents.
• Cook game meat thoroughly before eating.

Until recently, a vaccine has been available to protect laboratorians routinely working with Francisella tularensis. This vaccine is currently under review by the US Food and Drug Administration (FDA) and is not generally available in the United States.

NIH genetic and rare disease info

• NIH info on Tularemia

Tularemia is a rare disease.

Tularemia Resources
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