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SHIC-Funded Collaborative Study Addresses Oral Fluid PRV PCR

Psuedorabies virus (PRV) ranks fourth on the Swine Health Information Center (SHIC) swine disease matrix due to the potential for introducing highly pathogenic PRV into the US from Asia, as well as its potential negative impact on exports. Improvements in PRV diagnostics, surveillance, control, and elimination remain relevant. A collaborative research project among the Canadian Food Inspection Agency (CFIA), USDA Agricultural Research Service (ARS), and Iowa State University addressed the need for PRV PCRs for swine oral fluid.

Historical PRV control and elimination used a strategy of exploiting the molecular biology of the virus in PRV DIVA (differentiation of infected from vaccinated animals) vaccines and tests. The PRV viral envelope includes up to 11 structural glycoproteins. One is designated as gB and is highly conserved and required for both viral replication and cell-to-cell spread of the virus. In contrast, another, gE is not required for PRV replication and is associated with virulence. Wild-type viruses contain both gB and gE, while PRV MLV vaccines contain gB, but not gE. This clear distinction between wild-type and modified live vaccine viruses has allowed for the development of a DIVA approach to PRV control and eradication. Gene-deleted vaccines are used to protect animals against clinical PRV, with differential antibody ELISAs or DNA PCRs used to detect infected animals.

This project evaluated the detection of PRV in swine oral fluids collected from vaccinated and/or inoculated pigs using two contemporary real-time PCR assays targeting PRV gB and gE genes. Results showed that PRV DNA could be detected in swine oral fluid specimens using PRV gB and gE real-time PCRs, giving the potential to differentiate wild-type from vaccine strain viruses in the fluids. Additionally, comparisons of detection rates in nasal swab vs oral fluid samples suggested that oral fluid could be used as an alternative to individual pig (nasal swab) sampling for PRV surveillance. However, further improvements in the performance of both the gB and gE PCRs would be recommended. Read the Industry Summary of the study here (Project #18-215).

Funded by America's pork producers to protect and enhance the health of the US swine herd, SHIC focuses its efforts on prevention, preparedness, and response. As a conduit of information and research, SHIC encourages sharing of its publications and research for the benefit of swine health. Forward, reprint, and quote SHIC material freely. For more information, visit http://www.swinehealth.org or contact Dr. Paul Sundberg at psundberg@swinehealth.org.