Submitted to: United States Animal Health Association Proceedings
Publication Type: Proceedings
Publication Acceptance Date: October 30, 1995
Publication Date: N/A
Interpretive Summary: Brucellosis causes abortion in cattle making it an economically important disease of the livestock industry. A new vaccine to prevent bovine brucellosis, B abortus RB51, is being tested in cattle A critical safety factor of brucellosis vaccines is the safe use in adult cows which may be pregnant. The current brucellosis vaccine in use, B. abortus strain 19 can induce abortion in a small percentage of pregnant cows. In order to evaluate the safety of B. abortus RB51 in pregnant cattle, pregnant heifers were inoculated with B. abortus RB51. Inoculation of pregnant cattle did not cause abortion, although tissues of the mother and calf were infected with the vaccine strain. Additionally, B. abortus RB51 induced inflammation of the placenta. These results show that B. abortus RB51 does not cause abortion in pregnant cattle, however, it suggests that further studies to evaluate the impact of fetal and placental infection are warranted. This information is particularly useful to APHIS regulatory personnel in the evaluation of B. abortus RB51 as an approved vaccine as well as other scientists in the field of brucellosis research.
B. abortus strain 19 had been an integral part of the bovine brucellosis eradication effort. However, it has some disadvantages including vaccine induced abortion in pregnant animals. A new vaccine, B. abortus strain RB51 has been tested in cattle and found to be protective as well as non-abortigenic in pregnant cattle. Intravenous experiments in pregnant cattle show that strain RB51 does induce placentitis in most infected cattle, however, this placentitis was not associated with abortion. In a small number of intravenously inoculated cattle premature birth occurred.