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The purpose of the present study was to determine whether oral fluid samples could be used to monitor individually-housed adult boars for PRRSV infection.
In 3 trials, 24 boars, 5.5 months to 4 years in age, were intramuscularly (IM) inoculated with a modified-live PRRSV (MLV) vaccine (Trial 1), a Type 1 PRRSV isolate (Trial2), or a Type2 isolate (Trial 3). Oral fluid samples were collected daily and serum samples were collected twice weekly. Following the completion of the study, samples were randomized and blind-tested for PRRSV by real-time quantitative reversetranscription polymerase chain reaction (qRT-PCR).
With the exception of 2 boars in Replicate 2, all boars were successfully trained to provide oral fluid samples. A total of 2088 oral fluid samples were attempted. i.e., 29 days x 24 boars x 3 trials, and 1954 (93%) samples were collected. The average volume of oral fluid collected per boar across all trials was 17.9 ml (rang: 1 to 39 ml). PRRSV was detected in oral fluids at DPI 1 and all oral fluid specimens were PRRSV qRTPCR positive at DPI 4. Although PRRSV was detected in both serum and oral fluid specimens through DPI21, a comparison of matched samples from individual boars showed that oral fluid was equal to serum for the detection of PRRSV at DPI 7 and more likely to be positive tan serum on DPI 14 and 21.
Overall, oral fluid was superior to serum for the detection of PRRSV using PCR over the 21 day observation period in this study. The data showed that oral fluid offers distinct advantages over serum for the purpose of monitoring individually-housed animals for PRRSV infection using qRTPCR. Advantages include easier simple collection, the ability to collect samples frequently (even daily) without incurring animal or employee resentment, the ability to select animals at random for sampling, and the cumulatively greater likelihood of detection in oral fluids vs serum. By extersion, oral fluid could replace blood sampling for monitoring PRRSV in other swine populations and in other application, such as PRRSV elimination/eradication programs.
A. Kittawornrat, M. Engle, W. Chittick, J. Johnson, D. Patnayak, C. Wang, D. Whitney, C. Olsen, J. Prickett, T. Schwartz, K. Schwartz, J. Zimmerman. Porcine Reproductive and Respiratory Syndrome virus (PRRSV) in serum and oral fluid samples from individual boars: will oral fluid replace serum for PRRSV surveillance?. 6th International Symposium on Emerging and Re-emerging Pig Diseases: 58
