Brucellosis is a contagious, costly disease. While most often found in ruminant animals (e.g., cattle, bison and cervids) and swine, brucellosis (also known as contagious abortion or Bang's disease) can affect other animals and is transmissible to humans. The disease is caused by a group of bacteria known scientifically as the genus Brucella. Three species of Brucella cause the most concern: B. abortus, principally affecting cattle, bison and cervids; B. suis, principally affecting swine and reindeer but also cattle and bison; and B. melitensis, principally affecting goats but not present in the United States. For more information, see Facts About Brucellosis.
While there is no cure for brucellosis, it can be avoided by practicing proper sanitation methods and herd management strategies such as maintaining closed herds, recording individual animal identification and maintaining accurate records, isolating and testing new animals and those re-entering the herd, and arranging diagnostic workups and/or necropsies for exposed and potentially infected animals. While signs of the disease may disappear, infected animals remain diseased and are dangerous sources of infection for other animals.
While the National Brucellosis Eradication Program continues to work towards this goal, the success of this Program depends on the support and participation of livestock producers. The basic approach has always been to vaccinate calves, test cattle and domestic bison for infection, and send infected animals to slaughter. Depopulation of herds, if funds are available, may be used if herds are severely affected. Identification of market animals for tracing, surveillance to find infected animals, investigation of affected herds, and vaccination of replacement calves in brucellosis-affected areas are important features of the current program. The Brucellosis Uniform Methods and Rules set forth the minimum standards for states to achieve eradication. States are designated brucellosis free when none of their cattle or bison is found to be infected for 12 consecutive months under an active surveillance program. (For a listing of state brucellosis classifications, see Status of Current Eradication Programs.)
APHIS conducts surveillance on animals at slaughter by testing their blood for presence of Brucella antibodies. Around two million animals are tested annually. Surveillance is more than sufficient to detect one affected herd out of 100,000 herds at a confidence level of 95%. Estimated prevalence is 0.002%.
Efforts to eradicate brucellosis caused by Brucella abortus in the United States began in 1934 as part of an economic recovery program to reduce the cattle population because of the Great Depression and concurrent severe drought conditions. A number of states saw this as an opportunity to reduce the level of brucellosis, which was the most significant livestock disease problem in the US at the time. In 1934 and 1935, the reactor rate in adult Cattle tested was 11.5%.
In 1954, the magnitude of the brucellosis problem in terms of economics to the cattle industry and human health prompted the United States Congress to appropriate funds for a comprehensive national effort to eradicate brucellosis. The brucellosis eradication program was designed as a cooperative effort between the federal government, the states, and livestock producers. National eradication in cattle was mostly achieved by the early 2000s, with now only an occasional spillover case in cattle in the GYA, but none elsewhere since 2010.