Submitted to: American Journal of Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/8/1996
Publication Date: N/A
Interpretive Summary: Brucellosis is an economically important disease of cattle causing abortion and reproductive loss. Brucellosis can cause reproductive losses in bison, which may transmit brucellosis to cattle. Therefore, it is important to cattleman and wildlife officials to control brucellosis in bison. The vaccine used in cattle to prevent brucellosis is not effective in bison and is not safe to use in pregnant bison. We tested an experimental vaccine, B. abortus strain RB51, in pregnant bison to determine its safety. Inflammation of the placenta and abortion occurred in some bison cows. We conclude that bison are more susceptible to the adverse effects of the vaccine and that tests using lower doses in pregnant bison are needed. This information is relevant to wildlife officials, vaccine licensing officials and cattle and bison producers.
Technical Abstract: To determine the abortifacient potential and placental tropism of the vaccine candidate Brucella abortus strain RB51 in bison, pregnant cows (n=10) were vaccinated subcutaneously with 1x10(9) CFU SRB51. Two bison aborted SRB51-infected fetuses at 68 and 107 days post- vaccination. When aborting cows were examined 5-weeks post-abortion, endometritis was evident and SRB51 was isolated from supramammary lymph nodes and uterus. Two SRB51-vaccinated cows euthanized and examined 5-weeks post-vaccination had placentitis with numerous SRB51 organisms within trophoblastic epithelial cells. SRB51 was isolated from placentomes, numerous lymph nodes, fetal tissues and fluids. Fetal lesions were not seen. These results show that SRB51 can induce abortion and placentitis in bison. Based on this study and previous findings in cattle and bison this suggests that bison may be more sensitive to the abortifacient effects of Brucella sp. and decreased dosages of SRB51 vaccine may be required to safely vaccinate pregnant bison.