Submitted to: American Journal of Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 18, 1997
Publication Date: N/A
Interpretive Summary: Porcine reproductive and respiratory syndrome (PRRS) is one of the most costly diseases currently faced by the United States swine industry. Clinical losses are due mainly to reproductive failure of pregnant gilts and sows, and respiratory tract disease in young pigs. In this study we investigated another facet of potential losses as a result of infection with PRRS virus (PRRSV), namely death and poor performance of liveborn pigs that are infected either congenitally or during early postnatal life. Our results indicated that such infection can have major economic impact in that debility and death are common among pigs infected congenitally or during early postnatal life. They also emphasize the importance of ensuring immunity, as for example through vaccination, in pregnant gilts and sows in an attempt to prevent congenital infection and to provide protective immunity through colostrum consumed by baby pigs.
Technical Abstract: Infection of susceptible gilts and sows during gestation with virulent strains of porcine reproductive and respiratory syndrome (PRRS) virus (PRRSV) often results in reproductive failure. The most common clinical features associated with either naturally occurring or experimentally induced cases are late-term fetal death, stillbirth, and weak and unthrifty neonatal pigs. In field cases, late-term abortion also is common, whereas under experimental conditions gestation is sometimes prolonged, especially when all or most of the litter dies in utero. Previous experimental investigations on the reproductive aspects of PRRS have focused mainly on the prenatal and immediate postnatal effects of transplacental infection. In the study reported here we extended these observations to better define the clinical effects of PRRSV during a longer (3-week) postnatal interval. Pregnant gilts at or about day 90 of gestation were exposed oronasally to either attenuated vaccine virus (RespPRRS) or 1 of 3 strains of virulent field virus. Their pigs were observed for clinical signs, and were tested at birth (presuckling) and at weekly intervals thereafter for virus, homologous antibody, and body weight.