Biosafety of parenteral Brucella abortus RB51 vaccine in bison calves

Vaccination is considered among the primary management tools for reducing b rucellosis prevalence in Greater Yellowstone Area (GYA) ungulates. Before t heir use, however, vaccine safety and efficacy must he demonstrated. Twenty -seven female bison (Bison bison) calves (approx 5 months old) were vaccina ted with Brucella abortus Strain RB51 (1.5 x 10(10) colony forming units [C FU], subcutaneously) as part of routine management. We assessed the persist ence, pathology, shedding, and transmission associated with KB51 by serial necropsy, bacteriology, histopathology, and serology of 20 of these 27 vacc inated calves, and RB51 serology HB51 serology of 10 nonvaccinated. comming ling adult females. With the exception of 1 calf, RB51 dot-blot titers at n ecropsy were <1:80. Strain HB51 was cultured from lymph nodes in 4 of 4 cal ves at 14 weeks postvaccination (PV), 4 of 4 calves at 18 weeks PV, 1 of 4 calves at 22 weeks PV, 3 of 4 at 22 weeks PV, and 3 of 4 at 26 weeks PV, an d 0 of 4, calves at 30 weeks PV. No gross lesions were observed. Mild histo logic changes occurred only in a few draining lymph nodes early in sampling . Adverse clinical effects were not observed in vaccinates. Swabs from naso pharynx, conjunctiva, rectum, and vagina were uniformly culture negative fo r RB51. Strain RB51 dot-blot assays of bison cows were negative at a 1:20 d ilution at 26 weeks PV. Our results suggest that KB51 persists longer in bi son calves than in domestic cattle and is systemically distributed within l ymphatic tissues. However, bison apparently clear the RB51 vaccine strain w ithout shedding, transmission, or significant adverse reactions.