Search

Objective: To evaluate clearance, antibody responses, potential shedding, and histologic lesions in reproductive tissues of adult bison bulls after vaccination with Brucella abortus strain RB51., Animals: 61 two- and 3-year-old bison bulls., Procedure: 12 bison bulls were vaccinated s.c. with B abortus strain RB51, 3 were inoculated s.c. with 0.15 M NaCl, and antibody responses were evaluated. Various specimens were obtained to evaluate bacterial shedding. Four vaccinates and 1 control were necropsied 10, 20, and 30 weeks after vaccination. In a separate experiment, bison bulls were vaccinated s.c. with 0.15 M NaCl, or by hand or ballistically with strain RB51. Antibody responses were monitored 6 weeks after vaccination and during necropsy 13 weeks after vaccination. Tissue specimens obtained during necropsy from both studies were evaluated bacteriologically and histologically., Results: Strain RB51 was recovered at various times from semen of 3 of 12 vaccinated bison bulls in experiment 1. During necropsy, strain RB51 was recovered 10 and 20, but not 30, weeks after vaccination. In experiment 2, strain RB51 was recovered from lymphoid tissues of hand- and ballistic-vaccinated bison bulls during necropsy. In both experiments, microscopic lesions in testes, epididymis, and seminal vesicles were minimal and did not differ between strain RB51-vaccinated and saline-inoculated bison bulls., Conclusions and Clinical Relevance: Strain RB51 does not induce relevant inflammatory lesions in reproductive tissues of adult bison bulls. Shedding of strain RB51 in semen may be transient in some bison bulls; however, the importance of this observation is unknown.

Objective: To determine the ability of Brucella abortus strain RB51 to induce placentitis and abortion in bison after SC vaccination., Animals: 10 pregnant bison cows, 3 to 10 years old and at 3 to 8 months' gestation., Procedure: Pregnant bison cows on a Montana ranch were vaccinated SC with 10(9) colony-forming units of B abortus strain RB51. Two cows, identified prior to the study, were euthanatized and examined 5 weeks after vaccination to obtain optimal histologic samples of placenta. Other cows were euthanatized and examined after abortion. After euthanasia, tissue specimens were collected for histologic and immunohistochemical evaluation. Tissue and fluid specimens for bacteriologic culture were also collected during necropsy., Results: Of 8 cows, 2 aborted at 68 and 107 days after vaccination. Aborting cows had endometritis. Strain RB51 was isolated from reproductive tissues and supramammary lymph nodes. Fetal lesions were not seen; however, fetal bronchial lymph nodes and amniotic fluid contained strain RB51. Cows examined 5 weeks after vaccination had placentitis and endometritis, with numerous bacteria within trophoblastic epithelial cells that were immunoreactive for strain RB51 antigen. Strain RB51 was isolated from placentomes and numerous lymph nodes. Fetal lesions were not seen 5 weeks after vaccination; however, strain RB51 was isolated from numerous lymph nodes and lung, allantoic fluid, and rectal swab specimens., Conclusions: The vaccine candidate B abortus RB51 has tropism for the bison placenta, and can cause placentitis, which induces abortion in pregnant bison. The vaccine dose used was similar to that being tested in cattle, but may not be appropriate for pregnant bison.