Brucellosis is a zoonotic disease of great animal welfare and economic implications worldwide known since ancient times. 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.
Each species of Brucella tends to be associated with a specific host, but other animals can be infected, especially when they are in close contact. Cattle are the usual hosts for Brucella abortus. This organism also causes brucellosis in bison, water buffalo, camels and elk, and occasionally affects other species.
Mixed farming of cows, buffaloes, sheep and goats has increased the risk of brucellosis where small ruminants act as primary hosts for B. melitensis and cattle as spillover host.
Brucellosis is a widespread reproductive disease, commonly causing abortion, death of young ones, stillbirth, retained placenta or birth of weak calves, delayed calving, male infertility, and marked reduction in milk yield.
The bacteria infect reproductive tissues, lymph nodes, and the spleen, and therefore cause inflammation, edema, and necrosis. In pregnant animals it causes placental lesions and increases the risks of abortion.
Brucellosis disease
