Bison and elk: Brucellosis seroprevalence on a shared winter range

All increase in the population of Yellowstone bison (Bison bison) and changes in their winter distribution have prompted concerns about the potential for bison to transmit brucellosis to cattle. Elk (Cervus elaphus) also are hosts for the disease organism and could play a role as reservoirs for the disease. Environmental conditions on the Madison-Firehole winter range promote a high degree of range overlap between bison and elk (53% in Dec to 76% in May). Radiocollared elk were located within 100 m of bison 18% of the time, and commingling between species was positively correlated with snowpack. We investigated the seroprevalence of elk of the Madison-Firehole winter range and made comparisons to other elk populations in the region as an indicator of potential for interspecies transmission of brucellosis in the wild. We found that the seroprevalence rate in the Madison-Firehole elk (3%; n = 73) was consistent with elk that do not commingle with bison (0-1%) and lower than in elk associated with supplemental feeding programs (25-37%). Despite high levels of commingling, the seroprevalence rate in the Madison elk herd suggests that interspecies transmission from bison to elk in the Madison-Firehole is low.