Biosafety of parenteral Brucella abortus RB51 vaccine in bison calves

Vaccination is considered among the primary management tools for reducing brucellosis prevalence in Greater Yellowstone Area (GYA) ungulates. Before their use, however, vaccine safety and efficacy must be demonstrated. Twenty-seven female bison (Bison bison) calves (approx 5 months old) were vaccinated with Brucella abortus Strain RB51 (1.5 × 1010 colony forming units [CFU], subcutaneously) as part of routine management. We assessed the persistence, pathology, shedding, and transmission associated with RB51 by serial necropsy, bacteriology, histopathology, and serology of 20 of these 27 vaccinated calves, and RB51 serology of 10 nonvaccinated, commingling adult females. With the exception of 1 calf, RB51 dot-blot titers at necropsy were