148 RISK OF TRANSMISSION OF BOVINE HERPESVIRUS (BHV-1) BY INFECTED SEMEN TO RECIPIENTS AND EMBRYOS

Abstract

Bovine herpesvirus-1 (BHV-1) causes a variety of economically important respiratory and reproductive problems, the latter including vulvovaginitis, endometritis and infertility. For that reason, several countries have eradicated the disease and others have schemes in progress to achieve freedom. Although there is a considerable amount of information about the risk of BHV-1 transmission through contaminated semen used for artificial insemination, there is no available evidence to indicate whether the resulting embryos, when used for embryo transter (ET), can lead to the transmission of BHV-1 to recipients and offspring. For this experiment, bull semen contaminated in vitro with BHV-1 at 10² TCID₅₀ mL^–1 (Colorado strain) and then cryopreserved was used for insemination (2 times at estrus) of BHV-1 seronegative, superovulated heifers (N = 18). Embryos were collected postmortem 7 days post-insemination and were washed according to the IETS recommendations (however without trypsin treatment) or left unwashed. On 4 occasions, washed embryos were transferred to BHV-1 seronegative recipients. The remaining embryos and other samples collected from the reproductive tract were tested for BHV-1 presence using the standard virus isolation test. In total, out of 144 unfertilized oocytes and embryos collected, 9 were ET quality. Most of the embryos were degenerated (N = 79) or unfertilized (N = 56). The 4 heifers, which each received a single morula-stage embryo, maintained seronegative status, but did not become pregnant. BHV-1 was detected in 43% (23/53) unwashed and 0% (0/57) of washed embryos, 78% (14/18) of follicular fluid samples, 89% (16/18) of oviductal epithelial cells, 78% (14/18) of endometrium, and 89% (16/18) of corpora lutea tissues. Results herein suggest that BHV-1 can be transmitted by infected semen to embryo donors. The resulting unwashed embryos may remain infectious. However, whether BHV-1 uninfected offspring can be produced by ET of BHV-1 contaminated embryos that are washed according to the IETS guidelines, remains to be determined.