Submitted to: Iowa Veterinary Medical Association
Publication Type: Proceedings
Publication Acceptance Date: January 26, 1997
Publication Date: N/A
Technical Abstract: Porcine reproductive and respiratory syndrome (PRRS) is a virus-induced disease of swine which was first recognized about 10 years ago. In 1991 its cause, the PRRS virus (PRRSV), was identified and since that time significant work has been accomplished in understanding the biology of the virus. Modified live vaccines (MLV) have been developed which are commercially available and considered to be protective; however, MLV use also confounds the diagnosis of PRRS in the field. This proceedings updates research completed in our laboratory as well as reviewing work completed by others which focuses on the diagnosis and prevention of PRRS. A test for differentiating one PRRSV isolate from another has been developed in our laboratory which has enabled us to evaluate the efficacy of a commercially available PRRSV-MLV as well as 3 PRRSV-MLV developed in our laboratory. Results from these studies demonstrate the vaccines perform similarly and can induce a cross-protective immunity in sows when administered 4 to 5 months prior to challenge. In a vaccine efficacy study with young pigs vaccinated and challenged 3 weeks later, we did not observe the same extent of cross-protective immunity which suggests the length of time between vaccination and challenge may be an important factor in the development of a protective immune response. Preliminary studies evaluating colostral immunity in piglets indicate the passively acquired PRRSV-specific antibodies may not fully protect piglets from infection with homologous or heterologous PRRSV. However, the antibodies can interfere with virus isolation from a piglet's serum, thus increasing the difficulty of diagnosing an ongoing PRRSV infection in piglets that have suckled sows containing PRRSV-specific antibody.