Submitted to: American Journal of Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 14, 1996
Publication Date: N/A
Interpretive Summary: A new vaccine, Brucella abortus strain RB51 has been developed for use against brucellosis in cattle. These studies were done to determine the effectiveness of a standard dose of vaccine in calves, and to determine the best age for vaccination. The studies of vaccine efficacy are required for licensure of the vaccine, and for production of vaccine by a commercial company. The beneficiaries of the results are the beef cattle industry (better vaccine and lower production costs) and the consumer (cheaper beef). To determine the protective effect of the new vaccine when given at different ages, calves were vaccinated at 3, 5, 7, or 10 months. None of the vaccinated heifers developed antibodies in their serum that would interfere with diagnostic tests used to diagnose brucellosis in cattle in the field. When challenged during their first pregnancy with virulent bacteria, calves that had been vaccinated at 3 months of age were protected. Vaccination at 5 and 8 months of age gave equivalent, but less than complete protection. Data from this study suggest that the new vaccine RB51 is protective at doses comparable to those used for vaccines now in use when given to calves at 3 to 10 months of age.
To determine the protective effect of the new vaccine Brucella abortus strain RB51 when given at different ages, Polled Hereford heifer calves were inoculated subcutaneously at 3, 5, or 7 months with live cells of B. abortus strain RB51 (n=29), strain 19 (n=22), or sterile saline (n=12). None of the heifers given strain RB51 developed antibodies that reacted in the standard tube tests, but sera did have antibodies that reacted in a dot-blot assay RB51 antigen. When challenged during their first pregnancy with virulent B. abortus strain 2308, heifers vaccinated at 3 months were 100% protected. Vaccination at 5 and 8 months of age gave equivalent but less than complete protection. Heifers given strain 19 were 95% protected and controls had a high incidence of infection and abortion. Data from this study suggests that B. abortus strain RB51 is protective at vaccine doses comparable to those used for strain 19 when given to calves at 3 to 10 months of age.