No abstract

The purpose of the present study was to evaluate the diagnostic performance of a commercial serum antibody enzyme-linked immunosorbent assay (ELISA) modified to detect anti– Porcine reproductive and respiratory syndrome virus (PRRSV) antibodies in pen-based oral fluid specimens. Experimental and field oral fluid samples of defined status in reference to exposure of swine with PRRSV were used to derive the kinetics of detectable concentrations of antibody against PRRSV. Immunoglobulin (Ig)M and IgA were readily detected in oral fluid specimens from populations in which PRRSV infection was synchronized among all individuals but not in samples collected in commecial herds. In contrast, IgG was readily detected at diagnostically useful levels in both experimental and field samples for up to 126 days. Estimates of the IgG oral fluid ELISA performance were based on results from testing positive oral fluid samples ( n = 492) from experimentally inoculated pigs ( n = 251) and field samples ( n = 241) and negative oral fluid samples ( n = 367) from experimentally inoculated pigs ( n = 84) and field samples ( n = 283). Receiver operating characteristic analysis estimated the diagnostic sensitivity and specificity of the assay as 94.7% (95% confidence interval [CI]: 92.4, 96.5) and 100% (95% CI: 99.0, 100.0), respectively, at a sample-to-positive ratio cutoff of ≥0.40. The results of the study suggest that the IgG oral fluid ELISA can provide efficient, cost-effective PRRSV monitoring in commercial herds and PRRSV surveillance in elimination programs.

Pen-based oral fluid sampling has proven to be an efficient method for surveillance of infectious diseases in swine populations. To better interpret diagnostic results, the performance of oral fluid assays (antibody- and nucleic acid-based) must be established for pen-based oral fluid samples. Therefore, the objective of the current study was to determine the probability of detecting Porcine reproductive and respiratory syndrome virus (PRRSV) infection in pen-based oral fluid samples from pens of known PRRSV prevalence. In 1 commercial swine barn, 25 pens were assigned to 1 of 5 levels of PRRSV prevalence (0%, 4%, 12%, 20%, or 36%) by placing a fixed number (0, 1, 3, 5, or 9) of PRRSV-positive pigs (14 days post PRRSV modified live virus vaccination) in each pen. Prior to placement of the vaccinated pigs, 1 oral fluid sample was collected from each pen. Thereafter, 5 oral fluid samples were collected from each pen, for a total of 150 samples. To confirm individual pig PRRSV status, serum samples from the PRRSV-negative pigs ( n = 535) and the PRRSV vaccinated pigs ( n = 90) were tested for PRRSV antibodies and PRRSV RNA. The 150 pen-based oral fluid samples were assayed for PRRSV antibody and PRRSV RNA at 6 laboratories. Among the 100 samples from pens containing ≥1 positive pig (≥4% prevalence) and tested at the 6 laboratories, the mean positivity was 62% for PRRSV RNA and 61% for PRRSV antibody. These results support the use of pen-based oral fluid sampling for PRRSV surveillance in commercial pig populations.