Risks of transmission of spongiform encephalopathies by reproductive technologies in domesticated ruminants

Abstract

This paper considers whether transmissible spongiform encephalopathies (TSEs or prion diseases) could be spread by artificial insemination, embryo transfer and other more advanced reproductive technologies which are used for genetic improvement and also for purposes such as production of recombinant drugs for medical use. Although the technologies are most used in cattle, they are increasingly used in sheep, goats and deer as well, all of which can be naturally affected by TSEs. In general, provided appropriate precautions are taken, the risks of TSE carriage specifically by the gametes (spermatozoa and oocytes) or by in-vivo-derived embryos per se appear to be negligible, but further research, some of which is already in progress, will be helpful to give assurance on this point. Greater concerns relate to the many biological products that are used in the technologies, e.g. pituitary hormones used for the superovulation of donors, and various tissues and blood products used in semen and embryo culture/transport media, some of which have the potential to carry TSE infectivity if derived from infected animals. The myriad instruments and items of technical equipment that are used also give cause for concern because if they become contaminated with TSEs they may, due to their construction, be impossible to sterilise properly.