Embryo transfer and biosecurity: safeguarding healthy reproductive technologies in veterinary medicine

Embryo transfer (ET) is an essential reproductive biotechnology tool that supports genetic improvement, conservation programs and international germplasm trade across livestock species. Compared to the movement of live animals or semen, transport of properly collected and processed embryos presents a substantially lower biosecurity risk, owing to the protective role of intact zona pellucida, combined with standardized sanitary procedures established by the International Embryo Transfer Society (IETS) and the World Organization for Animal Health (WOAH). Rapid global expansion of in vitro produced (IVP) embryos, however, has introduced additional biosecurity considerations, as these embryos undergo multiple laboratory manipulations and are exposed to culture systems not encountered during in vivo development. Experimental evidence demonstrated that selected bacterial and intracellular pathogens may persist in IVP embryos following standard washing procedures under specific conditions; however, no confirmed outbreaks associated with commercially produced IVP embryos processed according to the standards have been reported. We summarize current evidence regarding pathogen transmission risks associated with ET; compare biosecurity characteristics of in vivo-derived (IVD) and IVP embryos; review current IETS and WOAH biosecurity guidelines; and discuss emerging challenges associated with continuing expansion of IVP technologies. Emphasis is placed on laboratory quality-control systems, donor health management and future research priorities needed to further strengthen international embryo biosecurity.