Based on the virus isolation test performed on embryos from the collected pool of each
individual donor, it cannot be determined whether transferred embryos were or were not contaminated with BVDV. It can only be inferred that some of the transferred embryos
were not infectious, because only a fraction of the washed embryos tested positive. It is also a possibility that the viral load associated with the embryos was below the minimal infectious dose. At the present time, there is no available quick and practical method to determine the viral load of embryos before their transfer. Also, a minimal infective dose of BVDV in association with a single embryo, necessary to produce disease via ET has not been determined as of yet. Nevertheless, the infectious residual viral amount associated with in vivo- and in vitro-fertilized embryos and oocytes after artificial exposure to BVDV and after sequentialwashingwas investigated by Gard et al.