INSEMINATION OF SUSCEPTIBLE AND PREIMMUNIZED GILTS WITH BOAR SEMEN CONTAINING PORCINE REPRODUCTIVE AND RESPIRATORY SYNDROME VIRUS

Twenty-one gilts without measurable PRRSV serum antibody titres were i dentified for this experiment. Seven gilts were used as controls (Grou p C) and 14 as principals. Of these, 7 gilts were preimmunized to PRRS V and constituted Group B, while 7 gilts remained seronegative and con stituted Group A. The principal gilts were inseminated with boar semen containing PRRSV and were killed 20 d later. The control gilts were t reated similarly but were not exposed to PRRSV. Gilts were observed fo r clinical signs of infection. The effects on the conception rates wer e studied and gilts and embryos were tested for PRRSV and homologous a ntibodies. Group A and B gilts developed signs of PRRS associated with anorexia and slightly elevated body temperatures. Transmission of the infection was demonstrated by the isolation of PRRSV from serum and o ther tissue samples of principal gilts and also by seroconversion. The results show that early infection may have an insignificant effect or no effect on the conception and fertilization rates. However, exposur e to PRRSV at the time of insemination can result in transplacental in fection of embryos. In Group A gilts, 5 of 6 litters were infected pre natally with 7.6% of embryos infected. In Group B gilts, 1 of 5 litter s and 1.3% of embryos were infected. Moreover, approximately 2 and 4 t imes more embryos were dead in litters of gilts from Group A and Group B than in gilts from control Group C. The isolation of PRRSV in 3 dea d embryos suggests that the embryos may have died as a result of the d irect effect of the virus. It can be concluded that the insemination o f either seronegative or preimmunized gilts with boar semen containing PRRSV may have an insignificant effect or no effect on conception and fertilization rates, although it can result in transmission of the vi rus and embryonic infection and death. (C) 1997 by Elsevier Science In c.