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Title: Parenteral Vaccination of Domestic Pigs with Brucella abortus strain RB51

item Stoffregen, William
item Olsen, Steven
item Bricker, Betsy

Submitted to: American Journal of Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/27/2006
Publication Date: 10/1/2006
Citation: Stoffregen, W.C., Olsen, S.C., Bricker, B.J. 2006. Parenteral Vaccination of Domestic Pigs with Brucella abortus strain RB51. American Journal of Veterinary Research. 67(10):1802-1808.

Interpretive Summary: The studies reported within this paper were conducted in order to evaluate the commercial vaccine Brucella abortus strain RB51 in domestic swine. RB51 has been previously evaluated in cattle and bison, and has been found to successfully prevent brucellosis in those species. Swine brucellosis is a bacterial disease caused by Brucella suis which causes abortions and chronic infections of multiple organs. The bacteria which cause brucellosis in swine are also capable of infecting humans who have contact with infected swine or swine products from infected animals. Currently there are no vaccines available to aid in the control of swine brucellosis; however, two previous reports suggested that RB51 would be useful in aiding the control and prevention of swine brucellosis. The work reported in this paper failed to identify a significant immunologic response of swine vaccinated with RB51. Also, there was a failure of the vaccine to induce protection against disease-causing Brucella suis in vaccinated animals. Therefore, the studies reported in this paper support the conclusion that RB51 is not a useful tool in controlling and preventing swine brucellosis.

Technical Abstract: Objective – To determine the immunogenicity and efficacy of Brucella abortus strain RB51(SRB51) as a vaccine in domestic swine. Animals – Experiment 1 (weaned pig experiment) contained 51 vaccinated, crossbred, domestic swine and 17 age-matched nonvaccinated, controls. Experiment 2 (bred gilt experiment) contained 18 vaccinated crossbred, domestic gilts and 8 age-matched, nonvaccinated controls. Procedures – In experiment 1 pigs were vaccinated with 2 X 10**10 cfu SRB51 or sham inoculated. Periodic bleedings were performed for blood culture, serology, and cell-mediated immunity assays. Necropsies were performed at selected time periods between week 1 and week 23 postvaccination to determine distribution and clearance of the vaccine. In experiment 2 gilts were similarly vaccinated or sham inoculated and similar postvaccination samples taken. Gilts were bred and challenged conjunctivally with 5.0 X 10**7 cfu virulent Brucella suis strain 3B. Necropsies were performed on gilts and neonates/fetuses after farrowing. Bacterial culture and serology were performed on necropsy samples to determine vaccine efficacy. Results – Humoral and cell-mediated immune responses did not differ between vaccinates and controls. SRB51 was not isolated postvaccination from blood cultures of either group and was isolated from lymphoid tissues of 3 animals at 2 weeks (n=2) and 4 weeks (n=1) postvaccination. There was no difference in isolation of B. suis or in seroconversion between vaccinated and control gilts and their neonates/fetuses. Conclusions – Parenteral vaccination with B. abortus strain RB51 does not induce significant humoral or cell-mediated immune responses. SRB51 did not protect gilts or their neonates/fetuses from virulent B. suis challenge.