Tularemia

Definition

Tularemia is an illness caused by a bacterium. It results in fever, rash, and greatly enlarged lymph nodes.

Description

Tularemia infects a variety of wild animals, including rabbits, deer, squirrels, muskrat, and beaver. Humans can acquire the bacterium directly from contact with the blood or body fluids of these animals, from the bite of a tick or fly which has previously fed on the blood of an infected animal, or from contaminated food or water.

Tularemia occurs most often in the summer months. It is most likely to infect people who come into contact with infected animals, including hunters, furriers, butchers, laboratory workers, game wardens, and veterinarians. In the United States, the vast majority of cases of tularemia occur in the southeastern and Rocky Mountain states.

Causes and symptoms

Five types of illness may occur, depending on where/how the bacteria enter the body:

• Ulceroglandular/glandular tularemia. Seventy-five to 85% of all cases are of this type. This type is contracted through the bite of an infected tick that has defecated bacteria-laden feces in the area of the bite wound. A tender red bump appears in the area of the original wound. Over a few weeks, the bump develops a punched-out center (ulcer). Nearby lymph nodes grow hugely swollen and very tender. The lymph nodes may drain a thick, pus-like material. Other symptoms include fever, chills, and weakness. In adults, the lymph nodes in the groin are most commonly affected; in children, the lymph nodes in the neck.
• Oculoglandular tularemia. This type accounts for only about 1% of all cases of tularemia. It occurs when a person's contaminated hand rubs his or her eye. The lining of the eyelids and the surface of the white of the eye (conjunctiva) becomes red and severely painful, with multiple small yellow bumps and pitted sores (ulcers). Lymph nodes around the ears, under the jaw, or in the neck may swell and become painful.
• Oropharyngeal and gastrointestinal tularemia. This type occurs when contaminated meat is undercooked and then eaten, or when water from a contaminated source is drunk. Poor hygiene after skinning and cleaning an animal obtained through hunting can also lead to the bacteria entering through the mouth. Sores in the mouth and throat, as well as abdominal pain, nausea and vomiting, ulcers in the intestine, intestinal bleeding, and diarrhea may all occur.
• Pulmonary tularemia. This rare type of tularemia occurs when a person inhales a spray of infected fluid, or when the bacteria reach the lungs through the blood circulation. A severe pneumonia follows.
• Typhoidal tularemia. This type of tularemia is particularly hard to diagnose, because it occurs without the usual skin manifestations or swelling of lymph glands. Symptoms include continuously high fever, terrible headache, and confusion. The illness may result in a severely low blood pressure, with signs of poor blood flow to the major organs (shock).

Diagnosis

Samples from the skin lesions can be prepared with special stains, to allow identification of the causative bacteria under the microscope. Other tests are available to demonstrate the presence of antibodies (special immune cells that the body produces in response to the presence of specific foreign invaders) which would be increasing over time in an infection with tularemia.

Treatment

Streptomycin (given as a shot in a muscle) and gentamicin (given as either a shot in a muscle or through a needle in the vein) are both used to treat tularemia. Other types of antibiotics have been tested, but have often resulted in relatively high rates of relapse (20%).

Prognosis

With treatment, death rates from tularemia are under 1%. Without treatment, however, the death rate may reach 30%. The pneumonia and typhoidal types have the worst prognosis without treatment.

Prevention

Prevention involves avoiding areas known to harbor ticks and flies, or the appropriate use of insect repellents. Hunters should wear gloves when skinning animals or preparing meat. Others (butchers, game wardens, veterinarians) who work with animals or carcasses should always wear gloves. A vaccine exists, but is usually only given to people at very high risk due to their profession or hobby (veterinarians, laboratory workers, butchers, hunters, game wardens).

Resources

ORGANIZATIONS

Centers for Disease Control and Prevention. 1600 Clifton Rd., NE, Atlanta, GA 30333. (800) 311-3435, (404) 639-3311. 〈http://www.cdc.gov〉.

KEY TERMS

Conjunctiva— The lining of the eyelids and the surface of the white part of the eye.

Shock— A state in which drastically low blood pressure prevents adequate blood flow to the tissues and organs throughout the body.

TULAREMIA

Tularemia is a potentially severe and fatal bacterial zoonosis caused by a gram-negative coccobacillus, Francisella tularensis. Tularemia occurs only in the Northern Hemisphere, most commonly in the United States and Europe. In nature, infection occurs mostly in rodents, rabbits, and hares. Humans become infected by handling infectious animal carcasses; eating or drinking contaminated food or water; being bitten by infective ticks, flies, or mosquitoes; or by inhaling contaminated aerosols. The disease is not transmitted person-to-person. The more severe F. tularensis strain A occurs only in the United States and Canada, while the milder strain B occurs throughout the Northern Hemisphere.

Tularemia in humans is relatively rare, and it takes several forms, depending on the route of inoculation. The ulceroglandular form is the most common. It is characterized by an ulcer that develops where infection has penetrated the skin, accompanied by painful swelling of nearby lymph glands. Other forms include the glandular, oculoglandular, oropharyngeal, pneumonic, intestinal, and septic ("typhoidal") types. Following a usual incubation period of three to five days (sometimes longer), all forms have similar acute onsets of fever, headache, musculoskeletal pain, progressive weakness, and weight loss. Patients with tularemia pneumonia typically develop a cough with minimal or no sputum production, chest pain, and difficulty in breathing. Patients with the septic form sometimes develop complications of bleeding, respiratory failure, and shock. All forms can be cured by treatment with antibiotics such as streptomycin, gentamicin, or tetracyclines. The disease can be fatal if not treated early with appropriate antibiotics.

Tularemia is best prevented by avoiding sick or dead animals, protecting against tick and insect bites, and by sanitary practices that protect against contamination of food and water by infected animals.

David T. Dennis

(see also: Vector-Borne Diseases; Zoonoses )

Bibliography

Beran, G. W. (1994). Handbook of Zoonoses, 2nd edition. Boca Raton, FL: CRC Press.

Dennis, D. T. (1998). "Tularemia." In Maxcy-Rosenau-Last Public Health and Preventive Medicine, 14th edition, ed. R. B. Wallace. Stamford, CT: Appleton & Lange.

tularemia or rabbit fever, acute, infectious disease caused by Francisella tularensis ( Pasteurella tularensis ). The greatest incidence is among people who handle infected wild rabbits. Tularemia may also be transmitted by other infected animals, ticks, or contaminated food or water. Within 10 days of contact the disease begins suddenly with high fever and severe constitutional symptoms. An ulcerating lesion (or several lesions) develops at the site of infection, such as the arm, eye, or mouth. The regional lymph nodes enlarge, suppurate, and drain. The infection may be complicated by pneumonia, meningitis, or peritonitis, and the mortality rate is about 6%. Treatment is with antibiotics. Continuous wet saline dressings can be beneficial for primary skin lesion.

Tularemia

Do Rabbits Cause Rabbit Fever?

How Do People Contract Rabbit Fever?

Is Tularemia Common?

What Are the Symptoms of Tularemia?

How Can a Doctor Tell if a Person Has Tularemia?

How Is Tularemia Treated?

Is There Any Way to Prevent Tularemia?

Resources

Tularemia (too-lah-REE-me-uh), sometimes called rabbit fever, is an infection caused by bacteria that can be spread to humans by wild animals.

KEYWORDS

for searching the Internet and other reference sources

Biological weapons

Bioterrorism

Francisella tularensis

Rabbit fever

Tick-borne diseases

Zoonoses

Do Rabbits Cause Rabbit Fever?

Tularemia is caused by the bacterium Francisella tularensis (fran-sih-SEL-uh too-lah-REN-sis). Most cases in the United States come from contact with infected rabbits and deer, although the bacterium also lives in other small mammals and birds, and it can be found in soil.

Tularemia bacteria enter the body through the mucous membranes*, the skin, the lungs, or the digestive system. There are seven different forms of the disease:

*mucous membranes

are the moist linings of the mouth, nose, eyes, and throat.

• Ulceroglandular tularemia comes from handling an infected animal or from the bite of a tick or deer fly. An ulcer (an open sore) forms on the skin.
• Glandular tularemia causes symptoms similar to those of the ulceroglandular form but an ulcer does not form. The bacteria may enter the body through small cuts in the skin. Most cases of rabbit fever in the United States are glandular or ulceroglandular tularemia.
• Oculoglandular tularemia comes from touching the eye with infected fingers. The eye becomes red and painful and has a discharge.
• Oropharyngeal tularemia comes from eating the undercooked meat of an infected animal or from drinking water contaminated by the bacterium. It causes digestive system symptoms, such as vomiting or diarrhea.
• Pneumonic tularemia is caused by inhaling spores (an inactive form of the germ enclosed in a protective shell) in dust from a contaminated area into the lungs. Other types of tularemia also may spread to the lungs.
• Typhoidal tularemia affects many organs of the body. This rare form of the disease occurs without any previous signs of infection in any specific part of the body.
• Septic tularemia is a severe form of the disease that affects the whole body. Someone with this form may go into shock* and experience serious complications.

*shock

is a serious condition in which blood pressure is very low and not enough blood flows to the body’s organs and tissues. Untreated, shock may result in death.

Is Tularemia the Next Anthrax?

It takes as few as 10 spores of the Francisella tularensis bacterium to infect someone with tularemia. The bacterium is hard to destroy and can be easily released into the air. For these reasons, experts on biological warfare fear that some groups might use tularemia as a weapon.

The United States stockpiled the bacteria during the 1960s but destroyed its stores in the 1970s at the order of the president. Russia, too, stockpiled and produced the bacteria through the mid-1990s.

There is no vaccine currently available in the United States. In the event of a bioterrorist attack, swift and widespread use of antibiotics could reduce the harmful effects of the disease.

How Do People Contract Rabbit Fever?

People cannot catch tularemia from one another. Most cases in the United States occur when someone gets a bite from a tick or deer fly that has previously bitten an infected rabbit or deer. Those in contact with infected animals may be infected by the bacterium through small cuts on the skin. Hunters contract tularemia from handling or eating undercooked, contaminated meat. In rare cases, bacterial spores survive in the soil and are released into the air; people then breathe the spores into their lungs. Drinking contaminated water is another rare but possible way to contract the disease.

Is Tularemia Common?

Tularemia occurs in the United States, Europe, and Asia, mainly in rural areas. Tularemia is highly infectious, but in the United States fewer than 200 cases are reported each year (mostly from Texas, Arkansas, and Oklahoma). Some additional cases may not be recognized and reported.

Tularemia affects people of every age, sex, and race. In spring and summer months, it occurs most often in children who become infected when playing outside. In fall and winter, hunters are more likely to contract the infection.

What Are the Symptoms of Tularemia?

Symptoms of tularemia depend on the form of the disease. Most infected people have a red spot at the site of the insect bite or cut where the bacterium entered the body. This becomes an ulcer.

Other signs and symptoms appear within 1 to 14 days (most frequently in 2 to 5 days) and may come on suddenly. They can include extreme tiredness, muscle aches, fever, headache, sweating, chills, and weight loss. Lymph nodes* in the groin and armpits may become swollen.

*lymph

(LIMF) nodes are small, bean-shaped masses of tissue that contain immune system cells that fight harmful microorganisms. Lymph nodes may swell during infections.

People who contract tularemia from inhaled bacteria usually have pneumonia*-like symptoms, such as a dry cough, shortness of breath, or discomfort in the chest area. This form can progress to shock and respiratory failure*.

*pneumonia

(nu-MO-nyah) is inflammation of the lung.

*respiratory failure

is a condition in which breathing and oxygen delivery to the body is dangerously altered. This may result from infection, nerve or muscle damage, poisoning, or other causes.

People who drink contaminated water or eat contaminated meat may experience nausea (NAW-zee-uh), vomiting, pain in the abdomen, diarrhea, sore throat, and sometimes gastrointestinal* bleeding.

*gastrointestinal

(gas-tro-in-TES-tih-nuhl) means having to do with the organs of the digestive system, the system that processes food. It includes the mouth, esophagus, stomach, intestines, colon, and rectum and other organs involved in digestion, including the liver and pancreas.

How Can a Doctor Tell if a Person Has Tularemia?

Doctors use blood tests to check for tularemia. Some tests look for antibodies* to the Francisella tularensis bacterium. Doctors also may look for evidence of the bacterium in the blood, fluid from the nose and mouth, and lymph nodes. If the person has symptoms of pneumonia, a chest X ray will be taken.

*antibodies

(AN-tih-bah-deez) are protein molecules produced by the body’s immune system to help fight specific infections caused by microorganisms, such as bacteria and viruses.

How Is Tularemia Treated?

Tularemia responds well to antibiotics, and most people can receive treatment at home. Because tularemia is not contagious, people who have it do not have to be isolated.

In more severe cases, when the disease attacks the lungs or other organs, people may require hospitalization and closer monitoring.

Most people who receive treatment recover from tularemia. The septic and pneumonic forms of the disease can be life threatening, however. Symptoms of tularemia can last for several weeks. Most people do not experience any lasting damage from the disease and may develop some degree of immunity* to it.

*immunity

(ih-MYOON-uh-tee) is the condition of being protected against an infectious disease. Immunity often develops after a germ is introduced to the body. One type of immunity occurs when the body makes special protein molecules called antibodies to fight the disease-causing germ. The next time that germ enters the body, the antibodies quickly attack it, usually preventing the germ from causing disease.

Complications of tularemia can include pneumonia, meningitis*, osteomyelitis*, kidney problems, lung abscesses*, pericarditis (inflammation of the sac surrounding the heart), shock, and, rarely, death.

*meningitis

(meh-nin-JY-tis) is an inflammation of the meninges, the membranes that surround the brain and the spinal cord. Meningitis is most often caused by infection with a virus or a bacterium.

*osteomyelitis

(ah-stee-o-my-uhLYE-tis) is a bone infection that is usually caused by bacteria. It can involve any bone in the body, but it most commonly affects the long bones in the arms and legs.

*abscess

(AB-ses) is a localized or walled off accumulation of pus caused by infection that can occur anywhere in the body.

Is There Any Way to Prevent Tularemia?

In the past, laboratory workers at risk for contracting tularemia because of frequent contact with laboratory animals were vaccinated against the disease. In 2003, the vaccine is not available for public use in the United States while the Food and Drug Administration performs further studies.

The best way to avoid contracting tularemia is to prevent tick bites by using repellent and wearing light-colored clothing that covers arms and legs. It is wise to avoid contact with certain wild animals, such as rabbits. Experts recommend that hunters wear rubber gloves when handling animals and that all meat be thoroughly cooked. Swimming in or drinking water that might be contaminated should be avoided.

See also

Bioterrorism

Meningitis

Osteomyelitis

Pneumonia

Tick-borne Infections

Zoonoses

Resources

Organizations

American College of Emergency Physicians, 1125 Executive Circle, Irving, TX 75038. The American College of Emergency Physicians provides advice about avoiding tick bites in the article “Tick Bites—They’re Not Just About Lyme Disease” posted at its website.

Telephone 800-798-1822 http://www.acep.org

U.S. Centers for Disease Control and Prevention (CDC), 1600 Clifton Road, Atlanta, GA 30333. The CDC is the U.S. government authority for information about infectious and other diseases. It has a web page explaining tularemia and how it can be used as a biochemical weapon.

Telephone 800-311-3435 http://www.cdc.gov