Submitted to: Porcine Reproductive and Respiratory Syndrome International Symposium
Publication Type: Proceedings
Publication Acceptance Date: June 21, 1999
Publication Date: N/A
Technical Abstract: Porcine reproductive and respiratory syndrome (PRRS) is a disease of swine caused by the PRRS virus (PRRSV). Diagnosis of this disease is dependent on the detection of virus-specific antibody or the detection of virus in the tissues of affected animals. This paper reviews methods for diagnosing an acute infection with PRRSV and the application of these techniques as epizootiologic tools in the field. Serology can be confounded by vaccine virus-induced antibody that can not be differentiated from field virus-induced antibody. Thus, demonstrating an acute infection by serology is limited to identifying antibody in a seronegative herd, rising antibody titers in paired sera, or the presence of antibody in pre-suckle sera from newborn and stillborn pigs (indication of in utero infection of the sow). Virus can be detected in swine tissues for many weeks after experimental infection by isolation of the virus and detection of viral proteins or nucleic acids. In general, younger swine will replicate PRRSV for a longe period of time than older swine; therefore, it is easier to detect a virus infection in younger animals. Based on experimental data, serum and lung tissue/lavage fluid may be the most consistent specimens to test for virus. Perhaps most important of all is that each animal can respond differently to a PRRSV infection and all swine on a farm will not be infected at the same time, this means that the more animals that are sampled the greater the chance of diagnosing a PRRSV infection. A field case involving a cluster of PRRS epizootics is used as an example of applying molecular genetics as an epizootiological tool. Results from this study indicated area spread of PRRSV occurred that did not involve the direct movement of swine or fomite.