Brucellosis may also occur in carnivores, including members of the dog family. Brucellosis in Yellowstone National Park bison was first reported in 1917 and an endemic infection has persisted since that time. Approximately 45 percent of the current bison herd tests seropositive for the antibody to Brucella . However, not all seropositive animals are currently infected with the bacterium. Therefore, the bacteria probably was transmitted from domestic livestock to bison.
Many elk residing in the Greater Yellowstone Area also test serologically positive for brucellosis.
The percentage of animals testing positive varies from location to location within the Greater Yellowstone Area and may be related in part to the concentration of animals on winter feed grounds. Brucellosis is typically transmitted through ingestion. The Brucella bacteria are transmitted in aborted tissues, reproductive tissues and discharges, especially just prior to, during, or soon after abortion or live birth. The bacterium may also be shed in milk for variable lengths of time. Although transmission has been shown to occur between and among cattle, bison, and elk under experimental conditions, the risk of transmission of brucellosis between bison and cattle in the wild has not been determined.