Brucella Bacteria in Goat's Milk
By Luis Pons
March 24, 2004
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
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
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
Diseases of Livestock Research Unit. ARS is the USDA's chief scientific
research agency, while APHIS protects and promotes U.S. agricultural health.