Noncytopathogenic and cytopathogenic bovine viral diarrhea-mucosal disease viruses do not affect in vitro embryonic development into the blastocyst stage

Bovine oocytes enclosed within follicular epithelial (FE) cells were exposed to noncytopathogenic or cytopathogenic strains of bovine viral diarrhea-mucosal disease virus (BVD-MDV). After culture at 39 degrees C in humidified air with 5% CO2 for 24 h, the oocytes matured and then in vitro fertilization was performed. Some of the fertilized oocytes developed into blastocysts from day 8 to day 10 (day 1: date of insemination), and the rate of development to blastocysts was the same as for the unexposed control oocytes. In the developmental medium, each strain of BVD-MDV was present at 10(3) to 10(6) TCID50/0.25 ml from day 3 to day 10, respectively and the virus was isolated from the FE cells at high titers and from the embryos at low titers on day 10. BVD-MDV antigen was detected in the cytoplasm of the FE cells by indirect immunofluorescence. These findings indicate that BVD-MDV replicates well in FE cells. The results of this study suggest that BVD-MDV replication in cells around embryos has no effect on bovine embryo development.