Submitted to: American Association of Veterinary Laboratory Diagnosticians
Publication Type: Proceedings
Publication Acceptance Date: 12/21/2000
Publication Date: N/A
Technical Abstract: Porcine reproductive and respiratory syndrome (PRRS) is a swine disease caused by the PRRS virus (PRRSV). It was first recognized in 1987 and has become the number one infectious disease problem for the swine industry causing acute reproductive failure in sows (abortions, stillborn, and weak-born pigs) and respiratory disease in young pigs. Diagnosing PRRSV-induced reproductive failure can be difficult because only a few aborted fetuses or stillborn pigs are usually presented to a diagnostic laboratory and they may not have been rapidly collected or adequately chilled during transport. PRRSV is seldom isolated under these conditions indicating a need to evaluate and perhaps improve diagnostic methods. The goal of this paper was to compare the sensitivity of several diagnostic techniques for detecting PRRSV. Fetuses from sows experimentally infected with PRRSV were tested for PRRSV by virus isolation (VI), polymerase chain reaction, immunohistochemistry (IHC), and serology. Based on VI, about 40% of the fetuses were transplacentally infected. When compared to VI, serology (detecting PRRSV specific antibodies) appeared to be the least sensitive of the methods tested and IHC was better, detecting about 50% of the VI positive fetuses. Interestingly, viral antigen could be detected in thymic tissue of each of the IHC-positive fetuses. Polymerase chain reaction tests performed better than VI on tissues that underwent a treatment mimicking postmortem decomposition (storing the temperatures at various temperatures for up to 3 days). This study demonstrated the importance of properly handling tissues (keeping them cool) and submitting an adequate number of specimens to a diagnostic laboratory, since not every fetus within a litter is transplacentally infected.