Brucellosis

Definition

Brucellosis is a bacterial disease caused by members of the Brucella genus that can infect humans but primarily infects livestock. Symptoms of the disease include intermittent fever, sweating, chills, aches, and mental depression. The disease can become chronic and recur, particularly if untreated.

Description

Also known as undulant fever, Malta fever, Gibralter fever, Bang's disease, or Mediterranean fever, brucellosis is most likely to occur among those individuals who regularly work with livestock. The disease originated in domestic livestock but was passed on to wild animal species, including the elk and buffalo of the western United States. In humans, brucellosis continues to be spread via unpasteurized milk obtained from infected cows or through contact with the discharges of cattle and goats during miscarriage. In areas of the world where milk is not pasteurized, for example in Latin America and the Mediterranean, the disease is still contracted by ingesting unpasteurized dairy products. However, in the United States, the widespread pasteurization of milk and nearly complete eradication of the infection from cattle has reduced the number of human cases from 6,500 in 1940 to about 70 in 1994.

Causes & symptoms

The disease is caused by several different species of parasitic bacteria of the genus Brucella. B. abortus is found in cattle and can cause cows to abort their fetuses. B. suis is most often found in hogs and is more deadly when contracted by humans than the organism found in cattle. B. melitensis is found in goats and sheep and causes the most severe illness in humans. B. rangiferi infects reindeer and caribou, and B. canis is found in dogs.

A human contracts the disease by coming into contact with an infected animal and either allowing the bacteria to enter a cut, breathing in the bacteria, or by consuming unpasteurized milk or fresh goat cheese obtained from a contaminated animal. In the United States, the disease is primarily confined to slaughterhouse workers.

Scientists do not agree about whether brucellosis can be transmitted from one person to another, although some people have been infected from a tainted blood transfusion or bone marrow transplant. Newborn babies have also contracted the illness from their mothers during birth. Currently, it is believed that brucellosis can also be transmitted sexually.

The disease is not usually fatal, but the intermittent fevers (a source of its nickname, "undulant fever") can be exhausting. Symptoms usually appear between five days and a month after exposure and begin with a single bout of high fever accompanied by shivering, aching, and drenching sweats that last for a few days. Other symptoms may include headache, poor appetite, backache, weakness, and depression. Mental depression can be so severe that the patient may become suicidal.

In rare, untreated cases, the disease can become so severe that it leads to fatal complications, such as pneumonia or bacterial meningitis. B. melitensis can cause miscarriages, especially during the first three months of pregnancy. The condition can also occur in a chronic form, in which symptoms recur over a period of months or years.

Diagnosis

Brucellosis is usually diagnosed by detecting one or more Brucella species in blood or urine samples. The bacteria may be positively identified using biochemical methods or using a technique whereby, if present in the sample, the brucellosis bacteria are made to fluoresce. Brucellosis may also be diagnosed by culturing and isolating the bacteria from one of the above samples. Blood samples will also indicate elevated antibody levels or increased amounts of a protein produced directly in response to infection with brucellosis bacteria.

Treatment

Prolonged treatment with antibiotics, including tetracyclines (with streptomycin), co-trimoxazole, and sulfonamides, is effective. Bed rest is also imperative. In the chronic form of brucellosis, the symptoms may recur, requiring a second course of treatment.

Prognosis

Early diagnosis and prompt treatment is essential to prevent chronic infection. Untreated, the disease may linger for years, but it is rarely fatal. Relapses may also occur.

Prevention

There is no human vaccine for brucellosis, but humans can be protected by controlling the disease in livestock. After checking to make sure an animal is not already infected, and destroying those that are, all livestock should be immunized. Butchers and those who work in slaughterhouses should wear protective glasses and clothing, and protect broken skin from infection.

Some experts suggest that a person with the disease refrain from engaging in unprotected sex until free of the disease. The sexual partners of an infected person should also be closely monitored for signs of infection.

Key Terms

Antibody

A specific protein produced by the immune system in response to a specific foreign protein or particle called an antigen.

Chronic

Disease or condition characterized by slow onset over a long period of time.

Parasite

An organism living in or on, and obtaining nourishment from, another organism.

Pasteurization

The process of applying heat, usually to milk or cheese, for the purpose of killing, or retarding the development of, pathogenic bacteria.

Further Reading

For Your Information

Books

• Adams, L. Garry, ed. Advances in Brucellosis Research. Texas A&M University Press, 1990.
• Bannister, Barbara A., Norman T. Begg, and Stephen H. Gillespie. Infectious Disease. Oxford, England: Blackwell Scientific, Inc., 1996.
• Madkour, M. Monir. Brucellosis. Butterworth-Heinemann, 1989.
• Nielsen, Klaus and Robert J. Duncan. Animal Brucellosis. CRC Press, 1990.
• Van De Graaff, Kent. Survey of Infectious and Parasitic Diseases. New York: McGraw Hill, 1996.
• Wilks, David, Mark Farrington, and David Rubenstein. The Infectious Diseases Manual. Oxford, England: Blackwell Scientific, Inc., 1995.

  Periodicals

• Ruben, Bruce, et al. "Person-to-Person Transmission of Brucella melitensis." The Lancet. 337 (Jan. 5, 1991): 8732.

  Organizations

• Centers for Disease Control. 1600 Clifton Rd., NE, Atlanta, GA 30333. (404) 639-3311. http://www.cdc.gov/travel/travel.html.
• National Institute of Allergies and Infectious Diseases, Division of Microbiology and Infectious Diseases. Bldg. 31, Rm. 7A-50, 31 Center Drive MSC 2520, Bethesda, MD 20892.
• World Health Organization (WHO), Division of Emerging and Other Communicable Diseases Surveillance and Control. 1211 Geneva 27, Switzerland. http://www.who.ch.

  Other

• Bacterial Diseases (Healthtouch). http:www.healthtouch.com/level1/leaflets/105825/105826.htm.
• Emerging Infectious Diseases Journal, National Center for Infectious Diseases. http://www.cdc.gov/ncidod/EID/eidtext.htm.

Gale Encyclopedia of Medicine. Gale Research, 1999.