Rl. Cravens et al., EFFICACY OF A TEMPERATURE-SENSITIVE MODIFIED-LIVE BOVINE HERPESVIRUS TYPE-1 VACCINE AGAINST ABORTION AND STILLBIRTH IN PREGNANT HEIFERS, Journal of the American Veterinary Medical Association, 208(12), 1996, pp. 2031
Objective-To evaluate the efficacy of a commercially available tempera
ture-sensitive modified-live bovine her pesvirus type-1 (BHV-1) vaccin
e against BHV-1 challenge-induced abortion and stillbirth. Design-Pros
pective randomized control trial. Animals-20 cycling, nonpregnant, BHV
-1 seronegative heifers of various breeds and weights, 12 to 15 months
old. Procedure-Heifers were randomly assigned to a vac cinate (n = 10
) or nonvaccinate control (n = 10) group. Seventeen td 26 days after m
embers of the vaccinate group received a second dose oi vaccine, all h
eifers were artificially inseminated. Heifers were challenged intraven
ously with Cooper strain BHV-1 between days 177 and 187 of gestation.
Aborted fetuses and stillborn calves were necropsied, and tissues coll
ected for histologic examination and virus isolation. Heifers, calves,
and fetuses were tested for BHV-1 antibody throughout the study. Resu
lts-The difference in number of abortions or still-births between vacc
inated heifers (1/10) and control heifers (10/10) was significant (P <
0.003). Seven of 10 control heifers had a virus neutralization antibo
dy titer to BHV-1 at abortion or stillbirth that declined or remained
unchanged from their titer at a previous serologic evaluation (7 to 66
days earlier). Clinical Implications-Prebreeding vaccination of repla
cement heifers with modified-live BHV-1 vaccine provides fetal protect
ion at 6 months of gestation (7 months after vaccination) and appears
to be a reasonable precaution to control economic losses associated wi
th BHV-1 infection-Abortions induced by BHV-1 are not necessarily asso
ciated with rising or markedly high virus neutralization antibody tite
rs. These titers should be used cautiously when assessing the role of
BHV-1 in bovine abortion and stillbirth.