Evaluation of the safety of vaccinating mares against equine viral arteritis during mid or late gestation or during the immediate postpartum period and infection of embryos following insemination of donor mares with equine arteritis infective semen

Abstract

Scope and Method of Study: Randomized controlled studies

Findings and Conclusions: All mares vaccinated in mid gestation foaled without any problems, but 3 mares vaccinated in late gestation aborted. Vaccinating mares during the last 2 months of gestation was associated with a risk of abortion; this risk must be weighed against the much greater risk of widespread abortions in unprotected populations of pregnant mares naturally infected with EAV. When embryo transfer is performed after breeding with EAV infective semen, it is apparent that the IETS washing protocol does not fully remove EAV virus from the embryo, as virus could be detected on a small number of embryos, and a minority of mares seroconverted following embryo transfer. In conclusion, we inferred that the washing protocol of 10 washes and two trypsin treatments did not eliminate EAV from all embryos; due to limitations in experimental design, this requires confirmation. Furthermore, there may be a risk of EAV transmission associated with in vivo embryo transfer from a donor mare inseminated with EAV infective semen.