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. 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.
Brucellosis is caused by several different species of parasitic bacteria of the genus Brucella. 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.
Some people have reportedly been infected with the disease through blood transfusion or bone marrow transplant. Newborn babies have also contracted the illness from their mothers during birth. It is believed that brucellosis can also be transmitted sexually. The disease is not usually fatal, but the fevers 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. Infection by the Brucella bacteria B. melitensis can cause miscarriage, especially during the first three months of pregnancy. Brucellosis can also occur in a chronic form, in which symptoms recur over a period of months or years. Brucellosis is usually diagnosed by detecting one or more Brucella species in blood or urine samples.
Blood samples will also indicate elevated antibody levels or increased amounts of a protein produced directly in response to infection with brucellosis bacteria. Early diagnosis and prompt treatment is essential to prevent chronic infection. Untreated, the disease may linger for years, but it is rarely fatal. Prolonged treatment with antibiotic drugs, including tetracyclines (with streptomycin), co-trimoxazole, and sulfonamides, is effective. Bed rest is also important. In the chronic form of brucellosis, the symptoms may recur, requiring a second course of medication.
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.