Sanitary risks related to embryo transfer in domestic species

When using embryo transfer (ET), sperm and oocytes are potential sources of pathogens (bacteria, viruses, prions). Additionally, contamination may result from environmental conditions through which embryos are produced (in vivo or in vitro) and from the various manipulations performed before or during transfer into the recipient. The current problems with BSE emphasize the need to acquire more insight into the mechanisms of transmission of so called ''slow viruses''. Most studies have demonstrated that transmission of a given pathogen through ET is even different from one species to another and, within species, from one pathogen to another. The sanitary risk seems directly related to the adsorption of pathogens into the zona pellucida (ZP). Recent studies suggest that the sanitary risks may be more important with in vitro than with in vivo produced embryos, due to differences in the ZP of in vitro produced embryos, enabling easier adsorption of pathogens and to the use of biological products for culture. Evaluation of the potential risks associated with ET and efficiency of washing procedures should be assessed separately for in vivo and in vitro produced embryos. (C) 1996 by Elsevier Science Inc.