Immune Responses and Efficacy of Brucella Abortus Strain RB51 in Bison After Delivery in a Dry Dart Formulation or by Parenteral Inoculation.

Bison (Bison bison) heifer calves (n = 32) were randomly assigned to control or vaccination with 1010 colony-forming units of Brucella abortus strain RB51 (RB51) vaccine by single or boostered parenteral delivery, or by surgical implantation of a dry dart formulation (n = 8/trt). Serum and/or peripheral blood mononuclear cells (PBMC) were obtained at 0, 4, 8, 13, 16, 21, and 24 wks after initial vaccination and at 0, 4, 8, 12, 15, 22, and 27 wks after booster vaccination to characterize humoral and cellular immune responses to RB51. Bison in both RB51 vaccination treatments demonstrated greater (P 0.05) proliferative responses when compared to responses of non-vaccinates. Bison were pasture bred and pregnant animals experimentally challenged in mid-gestation with 107 CFU of B. abortus strain 2,308. Bison in parenteral vaccination treatments had reduced (P 0.05) in most tissues when compared to non-vaccinated bison. The results of this study reaffirm the efficacy of boostered parenteral vaccination of bison with RB51 in preventing brucellosis. Our data also suggests that the novel dry dart RB51 formulation does not induce sufficient efficacy in bison after a single inoculation.