Risk of the transmission of BoHV-1 and embryo transfer

The transmission of BoHV-1 during embryo transfer remains unclear.

Proposed sources of BoHV-1

• oocytes and embryos from acutely or latently infected cows
• semen from acutely or latently infected bulls
• the cell lines used for the oocytes/embryo culture
• substances of bovine origin used in the culture media (bovine serum albumin, foetal calf serum, bovine oestrus serum etc.)

IETS guidelines

The International Embryo Transfer Society (IETS) is monitoring the epidemiological aspects connected with embryo transfer and other related techniques.
The Society regularly issues a set of guidelines for the control and prevention of spreading of infectious diseases through semen and transferred embryos. The IETS has described protocols for washing and trypsin treatment for successful removal of most of bovine pathogens from the surface of zona pellucida intact, in vivo-derived bovine embryos.

The following has been concluded concerning the risk of BoHV-1 transmission during embryo transfer:

• In vivo derived bovine embryos, after being washed in accordance with IETS recommendations pose minimal risk of BoHV-1 transmission through embryo transfer. Nonetheless adequate measures should always be taken as to minimise the risk of operating with PI or acutely infected donors.
• In vitro derived embryos potentially pose a higher risk of BVDV and BoHV-1 spreading due to the differences in the characteristics of zona pellucida in comparison the in vivo derived ones as well as due to an increased risk of their contamination with these infectious agents through culture media and co-culture cell lines
• Ideally all media supplements and co-culture cell lines used in IVM and IVF techniques should be screened for the contamination with BVDV and BoHV-1