Efficacy of bovine herpesvirus-1 inactivated vaccine against abortion and stillbirth in pregnant heifers.

OBJECTIVE To evaluate the efficacy of an inactivated bovine herpesvirus-1 (BHV-1) vaccine to protect against BHV-1 challenge-induced abortion and stillbirth. DESIGN Prospective study. ANIMALS 35 beef heifers. PROCEDURES Before breeding, heifers were vaccinated with a commercially available BHV-1 inactivated vaccine SC or IM. The estrous cycle was then synchronized, and heifers were artificially inseminated 30 to 60 days after vaccination. Heifers (n = 21) were challenge inoculated IV at approximately 180 days of gestation with virulent BHV-1. Fourteen control heifers were not vaccinated. Clinical signs of BHV-1 infection were monitored for 10 days following challenge; serologic status and occurrence of abortion or stillbirth were evaluated until time of calving. RESULTS 18 of 21 (85.7%) heifers that received vaccine were protected from abortion following challenge, whereas all 14 control heifers aborted. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that an inactivated BHV-1 vaccine can protect against abortion resulting from a substantial challenge infection, with efficacy similar to that of modified-live BHV-1 vaccines.