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Q Fever

Q Fever

Definition

Q fever is an illness caused by a type of bacteria, Coxiella burnetii, resulting in a fever and rash.

Description

C. burnetii lives in many different kinds of animals, including cattle, sheep, goats, ticks, cats, rabbits, birds, and dogs. In sheep and cattle, for example, the bacteria tends to accumulate in large numbers in the female's uterus (the organ where lambs and calves develop) and udder. Other animals have similar patterns of bacterial accumulation within the females. As a result, C. burnetii can cause infection through contaminated milk, or when humans come into contact with the fluids or tissues produced when a cow or sheep gives birth. Also, the bacteria can survive in dry dust for months; therefore, if the female's fluids contaminate the ground, humans may become infected when they come in contact with the contaminated dust.

Persons most at risk for Q fever include anybody who works with cattle or sheep, or products produced from them. These include farm workers, slaughterhouse workers, workers in meat-packing plants, veterinarians, and wool workers. Since September 2001, however, Q fever has become an additional concern because of its potential as an agent of bioterrorism.

Q fever has been found all over the world, except in some areas of Scandinavia, Antarctica, and New Zealand.

Causes and symptoms

C. burnetii causes infection when a human breathes in tiny droplets, or drinks milk, containing the bacteria. After three to 30 days, symptoms of the illness appear.

The usual symptoms of Q fever include fever, chills, heavy sweating, headache, nausea and vomiting, diarrhea, fatigue, and cough. Also, a number of other problems may present themselves, including inflammation of the liver (hepatitis); inflammation of the sac containing the heart (pericarditis ); inflammation of the heart muscle itself (myocarditis ); inflammation of the coverings of the brain and spinal cord, or of the brain itself (meningoencephalitis); and pneumonia.

Chronic Q fever occurs most frequently in patients with other medical problems, including diseased heart valves, weakened immune systems, or kidney disease. Such patients usually have about a year's worth of vague symptoms, including a low fever, enlargement of the spleen and/or liver, and fatigue. Testing almost always reveals that these patients have inflammation of the lining of the heart (endocarditis ).

Diagnosis

Q fever is diagnosed by demonstrating that the patient's immune system is making increasing numbers of antibodies (special immune cells) against markers (antigens) that are found on C. burnetii.

Treatment

Doxycycline and quinolone antibiotics are effective for treatment of Q fever. Treatment usually lasts for two weeks. Rifampin and doxycycline together are given for chronic Q fever. Chronic Q fever requires treatment for at least three years.

Minocycline has been found to be useful in treating post-Q fever fatigue. The dosage is 100 mg per day for three months.

Prognosis

Death is rare from Q fever. Most people recover completely, although some patients with endocarditis will require surgery to replace their damaged heart valves.

Prevention

Q fever can be prevented by the appropriate handling of potentially infective substances. For example, milk should always be pasteurized, and people who work with animals giving birth should carefully dispose of the tissues and fluids associated with birth. Industries which process animal materials (meat, wool) should take care to prevent the contamination of dust within the plant.

Vaccines are available for workers at risk for Q fever.

Resources

BOOKS

Beers, Mark H., MD, and Robert Berkow, MD, editors. "Biological Warfare and Terrorism." In The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2004.

Beers, Mark H., MD, and Robert Berkow, MD, editors. "Q Fever." In The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2004.

PERIODICALS

Arashima, Y., K. Kato, T. Komiya, et al. "Improvement of Chronic Nonspecific Symptoms by Long-Term Minocycline Treatment in Japanese Patients with Coxiella burnetii Infection Considered to Have Post-Q Fever Fatigue Syndrome." Internal Medicine 43 (January 2004): 1-2.

Gami, A. S., V. S. Antonios, R. L. Thompson, et al. "Q Fever Endocarditis in the United States." Mayo Clinic Proceedings 79 (February 2004): 253-257.

Madariaga, M. G., J. Pulvirenti, M. Sekosan, et al. "Q Fever Endocarditis in HIV-Infected Patient." Emerging Infectious Diseases 10 (March 2004): 501-504.

Wortmann, G. "Pulmonary Manifestations of Other Agents: Brucella, Q Fever, Tularemia and Smallpox." Respiratory Care Clinics of North America 10 (March 2004): 99-109.

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

Antibodies Specialized cells of the immune system that can recognize organisms that invade the body (such as bacteria, viruses, and fungi). The antibodies are then able to set off a complex chain of events designed to kill these foreign invaders.

Antigens Markers on the outside of bacteria or viruses which can be recognized by antibodies.

Bioterrorism The use of disease microorganisms to intimidate or terrorize a civilian population.

Immune system The system of specialized organs, lymph nodes, and blood cells throughout the body which work together to prevent foreign invaders (bacteria, viruses, fungi, etc.) from taking hold and growing.

Inflammation The body's response to tissue damage. Includes increased heat, swelling, redness, and pain in the affected part.

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Q fever

Q fever

Q (or Query) fever is a disease that is caused by the bacterium Coxiella burnetii. The bacterium is passed to humans by contact with infected animals such as sheep, cattle, and goats, which are the main reservoirs of the microorganism. The disease, which was first described in Australia in 1935, can have a short-term (acute) stage and, in some people, a much longer, chronic stage.

The bacterium that causes Q fever is a rickettsia . Other rickettsia are responsible for Rocky Mountain Spotted Fever and trench fever, as examples. Coxiella burnetti and the other rickettsia are Gram-negative organisms, which need to infect host cells in order to grow and divide. Outside of the host the bacteria can survive, but do not replicate. Q fever differs from the other rickettsial diseases in that it is caused by the inhalation of the bacteria, not by the bite of a tick.

Groups most at risk to acquire Q fever are those who are around animals. These include veterinarians, sheep, cattle and dairy farmers, and workers in processing plants.

The bacteria are excreted into the environment in the milk, urine, and feces of the animals. Also, bacteria can be present in the amniotic fluid and the placenta in the birthing process. The latter is particularly relevant, as humans tend to be near the animals during birth, and so the chances of transfer of the bacterium from animal to human are great.

In addition, the microorganisms are hardy and can endure environmental stress. The chances for human infection are also increased because of the persistence of the bacteria in the environment outside of the animal host. Coxiella burnetii are very hardy bacteria, being resistant to antibacterial compounds, and to environmental stresses such as heat and lack of moisture. When present in a dry area, such as in hay or the dust of a barnyard, the organisms can be easily inhaled.

The entry of only a few live bacteria or even one living bacterium is required to cause an infection in humans. The environmental hardiness and low number of microbes required for an infection has made Coxiella burnetii a potential agent of bioterrorism.

Of those who become infected, only about half display symptoms. When symptoms of Q fever appear, they can include the sudden development of a high fever, severe headache, nausea, vomiting, abdominal pain, and an overall feeling of illness. Pneumonia and liver damage can develop in some people. Usually the symptoms pass in several months. However, the establishment of a chronic disease can occur, and is fatal in over 60 per cent of cases. The chronic form may not develop immediately after the transient disease. In fact, cases have been documented where the lapse between the initial disease and the chromic form was several decades. The chronic disease can lead to heart valve damage.

Why some people display symptoms of infection while others do not is still not resolved. Neither are the reasons why the disease is self-limiting within a short time in some people but develops into a lengthy, debilitating, and potentially lethal disease in other people.

Coxiella burnetii has two different forms, which have differing surface chemistries. These are called phase I and phase II. The phase I form is associated more with the chronic Q fever than is phase II.

Diagnosis of Q fever is most reliably obtained by the detection of antibodies to the infecting bacterium. Following diagnosis, treatment consists of antibiotic therapy. The antibiotics that have achieved the most success are fluoroquinolone, rifampin, and trimethoprim-sulfamethoxazole. In the chronic form of Q fever, the antibiotics may need to be administered for several years. If the disease has damaged body parts, such as heart valve, then treatment may also involve the replacement of the damaged tissues.

Vaccination against Q fever is not yet a standard option. A vaccine is available in Australia and parts of Europe, but has not yet been approved in North America.

Prevention of the transmission of the bacterium to humans involves the wearing of masks when around domestic animals and the prompt disposal of placenta and other tissues resulting from the birth process.

See also Bacteria and bacterial diseases; Zoonoses

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Q Fever

Q FEVER

Q fever is an infectious disease caused by the bacterium Coxiella burnetii. The "Q" derives from "query" fever, its name before the true cause of the disease was discovered in 1937. Worldwide in occurrence, the etiologic agent is prevalent in sheep, cattle, and goats, and it is also found in ticks, rodents, birds, dogs, and rabbits. Infections in animals are usually inapparent, but the disease can cause spontaneous abortions in animals. Humans can be very susceptible and can contract the disease through inhalation of contaminated dust or particles from animal hides, excreta, and birthing materials.

Because C. burnetii proliferates within human white blood cells called monocytes, it is protected from part of the human immune system. A complex molecule called a lipopolysaccharide, found on the surface of the organism, further protects it from host serum defense factors. Human disease will usually present with sudden onset of headache, fever, chills, muscle soreness, and (sometimes) pneumonia. Hepatitis or endocarditis are rarer complications. Without modern detection methods, the disease is difficult to diagnose, and many human infections are probably unrecognized. It is suspected that host and microbial factors combine to determine the severity of human disease.

The antibiotic tetracycline is usually very effective in treating acute Q fever. Chronic inflammatory forms of the disease, such as Q fever endocarditis or hepatitis, require more than one year of antibiotic treatment.

Outbreaks of human Q fever are commonly reported in Asia, Australia, and parts of Europe. The disease was made reportable in the United States in 1999. Transmission from human to human is uncommon. Control of Q fever depends upon its recognition in animal populations and the culling of infected animals to prevent subsequent human exposure. A commercial vaccine, Qvax, is available in Australia.

Herb A. Thompson

Jennifer McQuiston

(see also: Communicable Disease Control )

Bibliography

Centers for Disease Control and Prevention. Q Fever. Available at http://www.cdc.gov/ncidod/dvrd/qfever/index.htm.

Maurin, M., and Raoult, D. (1999). "Q Fever." Clinical Microbiology Reviews 12(4):518553.

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Q fever

Q fever n. an acute infectious disease of many animals, including cattle, sheep, goats, deer, and dogs, that is caused by a rickettsia, Coxiella burnetii. It is transmitted to humans primarily through inhalation of infected particles or consumption of contaminated unpasteurized milk, but also via ticks acting as vectors. A severe influenza-like illness develops, sometimes with pneumonia, after an incubation period of up to three weeks. Treatment with tetracyclines or chloramphenicol is effective. See also typhus.

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Q fever

Q fever: see rickettsia.

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