In a paper in BMC Veterinary Research, Apisit Kittawornrat of Iowa State University and co-authors there and with PIC North America and IDEXX Laboratories, Inc, report a study describing and contrasting the kinetics of the humoral response in serum and oral fluid specimens during acute PRRSV infection.

Their study involved three trials of 24 boars each. Boars were intramuscularly inoculated with a commercial modified live virus (MLV) vaccine (Trial 1), a Type 1 PRRSV field isolated (Trial 2), or a Type 2 PRRSV field isolate (Trial 3).

Oral fluid samples were collected from individual boars on day post inoculation (DPI) -7 and 0 to 21. Serum samples were collected from all boars on DPI -7, 0, 7, 14 21 and from four randomly selected boars on DPI 3, 5, 10 and 17. Thereafter, serum and oral fluid were assayed for PRRSV antibody using antibody isotype-specific ELISAs (IgM, IgA, IgG) adapted to serum or oral fluid.

The researchers observed statistically significant differences in viral replication and antibody responses were observed among the three trials in both serum and oral fluid specimens. PRRSV serum IgM, IgA, and IgG were first detected in samples collected on DPI 7, 10 and 10, respectively. Oral fluid IgM, IgA, and IgG were detected in samples collected between DPI 3 to 10, 7 to 10 and 8 to 14, respectively.

Kittawornrat and co-authors concluded that the study enhances our knowledge of the PRRSV humoral immune response and provided a broader foundation for the development and application of oral fluid antibody-based diagnostics.

They added that that anti-PRRSV antibody isotypes can be detected in oral fluid specimens, and that the results were compatible with previous reports describing the detection of anti-PRRSV antibody in both serum and oral fluid. Detection of PRRSV antibody in oral fluids collected from individual boars could provide an effective approach for monitoring PRRSV infection in boar studs.

Successful oral fluid collection and testing from individual boars suggests that approach could also be applied to population in production systems, such as pen-housed sows and farrowing crates.

Reference

Kittawornrat A., M. Engle, Y. Panyasing, C. Olsen, K. Schwartz, A. Rice, S. Lizano, C. Wang and J. Zimmerman. 2013. Kinetics of the porcine reproductive and respiratory syndrome virus (PRRSV) humoral immune response in swine serum and oral fluids collected from individual boars. BMC Veterinary Research, 9:61. doi:10.1186/1746-6148-9-61

Further Reading You can view the full report (as a provisional PDF) by clicking here. Find out more information on Porcine Reproductive Respiratory Syndrome (PRRS) by clicking here.

April 2013