Submitted to: United States Animal Health Association Proceedings
Publication Type: Proceedings
Publication Acceptance Date: October 7, 1999
Publication Date: N/A
Technical Abstract: Approximately fifty percent of adult bison in Yellowstone National Park are seropositive for brucellosis. In these studies, we evaluated the biosafety of the strain RB51 vaccine in adult bison bulls and its efficacy, when administered as a calfhood vaccine, in preventing fetal infection or abortion following midgestational challenge with a virulent B. abortus strain. In two separate studies, 42 adult bison were hand or ballisticall vaccinated with 10*10 colony-forming units of B. abortus strain RB51 and 19 were inoculated with saline. Strain RB51 persisted for up to 20 weeks in adult bison bulls. Transient shedding of strain RB51 in the semen, but not from mucosal surfaces, was detected in some bison bulls. Histologic lesions in reproductive tissues were insignificant and did not differ between vaccinates and nonvaccinates. Our results suggest that strain RB51 is safe in adult bison bulls. In a separate study, the efficacy of calfhood vaccination with strain RB51 to protect against midgestation exposure to a virulent B. abortus strain was evaluated. Both nonvaccinated bison aborted within 5 weeks after challenge and B. abortus strain 2308 was recovered from numerous maternal and fetal tissues. Five bison, which were calfhood vaccinated with strain RB51, delivered full-term, clinically healthy calves that were culture-negative for B. abortus. The challenge strain persisted in maternal lymphatic tissues of some RB51 vaccinates. Our study indicates that strain RB51 is efficacious as a calfhood vaccine in preventing Brucella-induced abortions or fetal infections, or shedding of B. abortus at parturition.