PRRSv ELISA limitations, SN antibody response, and viremia following repeated homologous exposures to wild-type virus in adult swine

摘要

Serology has been the cornerstone of swine disease monitoring and control. The presence of specific antibody in serum indicates prior exposure to disease, and may also confirm the animal possesses protective immunity. However, the antibody response following infection on the PRRSV ELISA is not permanant.Many animals return to seronegative status within 4 to 6 months after initial infection. Even more frustrating, there have been reports of animals returning to and remaining ELISA antibody negative during multiple repeated vaccinations with a modified live PRRSV vaccine. This diagnostic dilemma has been commonly observed in gilts receiving 3 PRRSV MLV immunizations prebreeding and then revaccinated following the traditional 6/60 vaccination program.If this response occurs after repeated frequent exposures to the same wild-type PRRSv, it would greatly reduce the usefullness of or significantly alter the way veterinarians need to interpret PRRSv ELISA test results for their clients. Low or negative antibody levels following multiple exposures to the same strain of wild-type PRRSv would make monitoring herds for continued virus circulation using the ELISA very difficult.