Abstract

Bovine herpesvirus 1 (BoHV-1) is a pathogen of major veterinary importance, causing principally reproductive failure, genital and respiratory disease in cattle. Since embryo transfer is a rapidly growing commercial venture, BoHV-1 has a significant negative impact  on  cattle  breeding  by  both  natural  and  artificial  service,  and  thereby  on  the  global livestock industry. Clinical infection of the reproductive tract causes infertility, early embryonic death and abortion. BoHV-1 may infect an embryo by either of two means. The first is through entry of contaminated sperm into the oocyte at the point of fertilization, while the second is via contact with either contaminated follicular fluid, oviductal or uterine tissues. In addition, the virus may infect the recipient cow if an infected embryo is transferred by assisted reproduction technology. This article briefly examines the two principal methods that are routinely available to eliminate BoHV-1,  performed  in  order  to  prevent  infection  of  bovine  embryos.  Although  each  offers  considerable benefits, it is also imperfect. Even after multiple trypsin washes BoHV-1  can  adhere  to  the  zona  pellucida  of  oocytes  and  pre-implantation  stage  embryos;  likewise,  cryopreservation  fails  to  eliminate  all  infectious  virus  particles.  A  more  experimental  technique,  sperm  processing,  shows  considerable  promise  but  requires  further validation as an effective way to remove BoHV-1 from bull semen before it can be recommended for industry-wide use.

Keywords

bovine herpesvirus 1, cattle, fertility, assisted reproduction, oocyte, semen, embryo, trypsin, swim-up, cryopreservation, sperm processing