THE PATHOGENICITY OF BRUCELLA-SUIS BIOVAR 4 FOR BISON

The pathogenicity of Brucella suis biovar 4 for bison (Bison bison) wa s evaluated by inoculation of 2.1 x 10(7) colony forming units (CFU) i n 0.1 ml saline into the conjunctival sac of six pregnant cows. Six pr egnant bison were inoculated with 1.27 X 10(7) CFU of Brucella abortus strain 2308 as a positive control. Bison were inoculated on 23 Januar y 1992 calving or abortion after which they were euthanized, and necro psied. Bacteriological and histological examinations were conducted on lymph nodes, reproductive tract, mammary gland, and internal organs. Terminal serum samples from calves and cows were evaluated by card, ri vanol precipitation, standard tube agglutination, cold complement fixa tion tube, indirect bison conjugated enzyme linked immunosorbent assay (ELISA), competitive ELISA, and particle-concentration fluorescence i mmunoassay. No clinical signs of brucellosis were seen in bison inocul ated with B. suis biovar 4, and infection was found only in lymph node s of two animals. There was no evidence of metastasis of this organism to the mammary gland or tile reproductive tract. There were no detect able levels of antibodies to Brucella spp. in terminal blood samples t aken from B. suis biovar 4-challenged bison. Brucella abortus was isol ated from several tissues in all control bison. All B. abortus-challen ged animals developed uterine infection and five developed mammary gla nd infection. Reproductive disease resulted in abortions in five B. ab ortus-challenged bison and neonatal death in the remaining calf. Bruce lla suis biovar 4 does not appear to be pathogenic for bison.