140 INTRAUTERINE INOCULATION OF CATTLE WITH BOVINE VIRAL DIARRHEA VIRUS SIMULTANEOUS TO TRANSFER OF IN VIVO-DERIVED BOVINE EMBRYOS

Abstract

Bovine viral diarrhea virus (BVDV) has been shown to be associated with single transferable in vivo-derived and in vitro-produced bovine embryos despite washing. Hence, the primary objective of this study was to evaluate the potential of BVDV to be transmitted via the intrauterine route at the time of embryo transfer. A total of 10 in vivo-derived Day 7 bovine embryos were nonsurgically collected from a BVDV negative and seronegative donor cow. After collection, embryos were washed in accordance with the International Embryo Transfer Society (IETS) standards. Following washing, embryos were placed into transfer media containing BVDV (SD-1; type 1a). The embryos were immediately aspirated into 0.25-mL straws and transferred into seronegative recipients (Day 0). The total quantity of virus transferred into the uterus of each recipient was 900 to 1000 cell culture infective dose 50 (CCID₅₀)/straw. This amount of virus was previously shown to be consistent with the average amount of BVDV associated with in vivo-derived and in vitro-produced embryos following standard IETS washing procedures after in vitro exposure to virus. The positive control heifer received 1.5 × 10⁶ CCID₅₀/straw of BVDV without an embryo. The negative control heifer received 1.5 × 10⁶ CCID₅₀/straw of heat-inactivated BVDV without an embryo. Serum and buffy coat samples were drawn from all heifers on Days 0, 3, 4, 6, 7, 8, 9, 10, 12, 15, and 30 after inoculation and analyzed for serum neutralizing antibodies and virus, respectively. The positive control heifer and all recipients of virus-exposed embryos exhibited viremia by Day 6 and seroconverted by Day 15. The negative control heifer did not exhibit viremia or seroconvert. All recipients receiving embryos were assessed for pregnancy using transrectal ultrasonography on Day 30 and 6 of 10 heifers were pregnant. On Day 60 the pregnant heifers were again assessed for pregnancy using transrectal ultrasonography. At this time only 1 of the 6 heifers was still pregnant. However, the fetus was determined to be nonviable and was removed via colpotomy. The fetus, fetal fluids and membranes were determined to be positive for BVDV via immunohistochemistry and PCR. Additionally, 213 base pairs of the 5′ nontranslated region of this PCR product were sequenced and found to be consistent with the inoculated strain. Results demonstrate that the average quantity of BVDV associated with bovine embryos after in vitro exposure and washing can result in viremia and seroconversion of seronegative recipients following transfer into the uterus during diestrus.