Exposure of gilts in early gestation to porcine reproductive and respiratory syndrome virus

Abstract

Twenty-five gilts without measurable serum antibody titres to porcine reproductive and respiratory syndrome virus (PRRSV) were identified and 16 were inoculated with PRRSV at seven, 14 or 21 days of gestation and killed 20 to 22 days later to determine the effect of the virus on their embryos. The remaining nine gilts were not exposed to PRRSV, but were killed at the same stages of gestation. The gilts were observed for clinical signs of infection and the gilts and their embryos were tested for PRRSV and homologous antibodies. The infection was demonstrated by the re-isolation of the virus and its detection by the reverse transcriptase polymerase chain reaction in serum and other tissue samples from the inoculated gilts, and also by seroconversion. However, the gilts remained healthy throughout the study, except for one which was depressed and anorexic for two days. Two of the litters from the gilts challenged with PRRSV on day 14 of gestation contained one and three infected live embryos; the other embryos from these two litters did not contain detectable virus, although most of the embryos in one of the litters were dead. The other nine litters from the gilts challenged with PRRSV and the control litters, showed no evidence of infection.

Effects of North American Porcine Reproductive and Respiratory Syndrome Virus (PRRSV)-Based Modified Live Vaccines on Preimmunized Sows Artificially Inseminated with European PRRSV-Spiked Semen

“…However, no North American PRRSV was detected in stillborn fetuses and live-born piglets. Although PRRSV may infect embryos during early gestation, it lacks the ability to kill embryos until late gestation (22). These data agree with those from our study, where most fetuses died in the last trimester of gestation.…”

Pathogenicity of three type 2 porcine reproductive and respiratory syndrome virus strains in experimentally inoculated pregnant gilts

“…The outcome of infection in pregnant sows and gilts largely depends on the stage of gestation. In early gestation, PRRSV can cause embryonic death (Prieto et al, 1996(Prieto et al, , 1997, while in mid-gestation the virus does not readily cross transplacentally and does not induce reproductive failure (Christianson et al, 1993;Kranker et al, 1998). PRRSV results in transplacental infection of fetuses and clinical manifestation characterized by abortions, early farrowings, fetal death, and the birth of weak, congenitally infected piglets resulting in elevated pre-weaning mortality (Cheon and Chae, 2001;Kranker et al, 1998;Mengeling et al, 1994;Terpstra et al, 1991).…”

Receptor-Determined Susceptibility of Preimplantation Embryos to Pseudorabies Virus and Porcine Reproductive and Respiratory Syndrome Virus

“…Because it has been shown that a transplacental infection of embryos can be established in a 20-day pregnancy [30], further research is needed to investigate at which developmental stage pig embryos become susceptible to a PRRSV infection.…”