title: Evaluation of the sensitivity of reverse-transcription polymerase chain reaction to detect porcine reproductive and respiratory syndrome virus on individual and pooled samples from boars.
abstract: Boar studs are continuously monitored for the presence of porcine reproductive and respiratory syndrome virus (PRRSV) by testing different biological samples by reverse-transcription polymerase chain reaction (RT-PCR). In most cases, samples are run in pools, even though the impact of pooling on the sensitivity of RT-PCR is unknown. The objective of this study was to evaluate the feasibility of using PCR on pooled samples through the estimation of the sensitivity of RT-PCR on different biological samples run individually, in pools of 3 and in pools of 5. Twenty-nine boars were inoculated with a low virulent PRRSV isolate. Serum, blood swab, and semen samples were obtained from each boar every 2 to 3 days for 2 weeks. Each sample was tested by RT-PCR undiluted or diluted 1:3 and 1:5 with negative samples. Eleven of the 29 boars did not appear to get infected from the inoculum, as evidenced by no seroconversion 15 days after inoculation. Data from the other 18 boars showed that serum was the best sample to detect PRRSV during acute infection, with the blood swab sample performing almost as well. Semen samples failed to detect PRRSV infection in most of the cases. Pooling samples at pool sizes of 3 and 5 resulted in a decrease in the sensitivity of RT-PCR. Sensitivity was reduced by 6% and 8%, respectively, when serum or blood swab samples were run in pools of 5. The impact of pooling on the sensitivity of PCR was higher in samples taken during the beginning of the viremic period.
authors.affiliation: Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN 55108, USA. rove0010@umn.edu
authors.forename: Albert
authors.initials: A
authors.lastname: Rovira
authors.forename: Travis
authors.initials: T
authors.lastname: Clement
authors.forename: Jane
authors.initials: J
authors.lastname: Christopher-Hennings
authors.forename: Bob
authors.initials: B
authors.lastname: Thompson
authors.forename: Mark
authors.initials: M
authors.lastname: Engle
authors.forename: Darwin
authors.initials: D
authors.lastname: Reicks
authors.forename: Claudia
authors.initials: C
authors.lastname: Muñoz-Zanzi
mesh_terms: D000818:Animals; D008297:Male; D019318:Porcine Reproductive and Respiratory Syndrome / Q000097:blood* / Q000175:diagnosis*; D019316:Porcine respiratory and reproductive syndrome virus / Q000302:isolation & purification*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary*; D012680:Sensitivity and Specificity; D013552:Swine