Test Detects Brucella Bacteria in Goat's Milk

Goat milk sold in the United States may soon be better protected against brucellosis-causing bacteria, thanks to recent research conducted by two U.S. Department of Agriculture agencies in Ames, Iowa.

A test for detecting the bacteria Brucella melitensis in bulk goat milk has been developed by research chemist Louisa Tabatabai of the Agricultural Research Service's National Animal Disease Center (NADC), Barbara Martin of the Animal and Plant Health Inspection Service's (APHIS) National Veterinary Services Laboratories, and graduate student Nathan Funk of Iowa State University. The test relies on an adaptation of an enzyme-linked immunoassay (ELISA) that Tabatabai helped develop in 1984 for testing cattle for B. abortus.

B. melitensis, one of six known species of Brucella bacteria that induce abortions in animals, mainly infects sheep and goats. In humans, B. melitensis infection causes Malta fever, which is characterized by fever and headaches.

Few cases of this infection in goats have occurred in the United States since 1972. But it is essential that vigilance be maintained to prevent introductions of the bacteria into the country. B. melitensis is particularly common in Latin America, central and southwest Asia, and the Mediterranean region.

Dairy goat milk is slowly gaining popularity due to its high protein and low cholesterol levels, as well as its compatibility for people with intolerance to cow's milk. About 1 million goats are raised for milk and cheese production in the United States.

In the studies, the assay--which detects B. melitensis antibodies--identified one goat with a high concentration of infection in a herd of more than 1,600 animals, and one goat with a low concentration in a herd of 50 animals. It also correctly identified all 13 positive and 134 negative bulk milk samples tested. The researchers recommend that herds be sampled in groups of 50 animals or less for bulk milk testing.

Tabatabai is in the NADC's Respiratory Diseases of Livestock Research Unit. ARS is the USDA's chief scientific research agency, while APHIS protects and promotes U.S. agricultural health.