As producers take on PRRS ARC projects, many factors related to preventing virus transmission need to be addressed. One factor that is a concern in Allegan and Ottawa counties is the level and intensity of infection among exhibition pigs. ARC project studies in other states have indicated that the level and intensity of PRRS infection in exhibition hogs is low. This was an area that needed further examination in Michigan.

To explore the issue locally, program coordinator and MSU Extension educator Beth Ferry worked with Allegan County Fair livestock leaders to test hogs that were exhibited at this year’s fair. Youth and parents involved in the market swine project were informed of the testing procedures and given the opportunity to opt out of having their animals tested. Most (87 percent) of the youth involved in the market swine project allowed their hogs to be tested, which resulted in pooled samples from about 130 hogs. Six students from the MSU College of Veterinary Medicine assisted in the PRRS testing.

Samples were sent to Iowa State University for polymerase chain reaction (PCR) testing and all of the animals tested negative for PRRS. The PCR test on oral fluids (saliva) only tests for the presence of virus being shed at the time of testing. This did not indicate if any of the animals had been exposed early in life and were no longer shedding the virus, which would result in a current negative PCR test.

At the present time there is no enzyme-linked immunosorbent assay (ELISA) test for saliva collection that can determine if a hog that tests negative on a PCR test has previously been exposed to PRRS but is no longer shedding the virus. An ELISA test for saliva collection is in the works, and all samples taken from the Allegan County Fair were frozen in preparation for the development of this technology. This technology is expected to be developed by January 2012. Completion of the ELISA testing on the exhibition pigs will allow project coordinators a better understanding of the instance of PRRS in this area of the industry.

Are you interested in getting involved or want to learn more about the project? More information about the West Michigan PRRS ARC project, including the quarterly newsletter, is available at http://pork.msue.msu.edu.