The transmission of bluetongue virus by embryo transfer in sheep

The susceptibility of sheep to intrauterine infection with bluetongue virus (BTV) was established by introducing 10(4) plaque-forming units of BTV type 10 into the uterine lumen of two seronegative ewes in a simulated embryo transfer operation. Both ewes became viraemic and underwent seroconversion to BTV. Embryos recovered from seronegative superovulated donor ewes were incubated in vitro for 8 h with BTV type 10. After incubation the embryos were thoroughly rinsed by repeated transfer to sterile culture medium, and 12 of these embryos were then transferred to the uterus or oviduct of seronegative, synchronized recipients. Viraemia and seroconversion were detected in nine recipient ewes. Embryos recovered from eight viraemic ewes were transferred to 15 seronegative, synchronized recipients. Viraemia and seroconversion were detected in 2 of the recipients, both of which also became pregnant. A lamb born to a ewe becoming infected at the time of embryo transfer was clinically normal, and no evidence of BTV infection was obtained at postmortem examination of the lamb after slaughter.