Evaluation of two real-time polymerase chain reaction assays for Porcine epidemic diarrhea virus (PEDV) to assess PEDV transmission in growing pigs. (January 2016)

• Record Type: Journal Article
• Authors: Miller, Laura C.; Crawford, Kimberly K.; Lager, Kelly M.; Kellner, Steven G.; Brockmeier, Susan L.
• Is Part Of: Journal of veterinary diagnostic investigation. Volume 28:Number 1(2016:Jan.)
• Page Start: 20
• Page End: 29
• Publication Date: 2016-01
• Subjects: Porcine epidemic diarrhea virus -- real-time reverse transcription polymerase chain reaction -- swine; Veterinary medicine -- Diagnosis -- Periodicals; 636.0896075
• DOI: 10.1177/1040638715621949
• Languages: English
• ISSNs: 1040-6387

Abstract

In April 2013, a Porcine epidemic diarrhea virus (PEDV) epidemic began in the United States. As part of the response, real-time reverse transcription polymerase chain reaction (RT-PCR) assays to detect PEDV were developed by several veterinary diagnostic laboratories. Our study evaluated RT-PCR PEDV assays that detect the N gene ( gN ) and S gene ( gS ) for their ability to detect PEDV infection and the transmission potential of pigs experimentally exposed to PEDV. Detection limits and quantification cycle (Cq) values of real-time RT-PCR were assayed for PEDV samples and positive controls for both gN and gS . The limit of detection for the gN assay was 10 −6 (mean Cq: 39.82 ± 0.30) and 10 −5 (mean Cq: 39.39 ± 0.72) for the gS assay with PEDV strain USA/Colorado/2013. Following recommended guidelines, rectal swabs ( n = 1, 064) were tested; 354 samples were positive by gN assay and 349 samples were positive by gS assay (Cq ≤ 34.99), 710 samples were negative by gN assay and 715 were negative by gS assay (Cq > 34.99) of which 355 and 344 were "undetermined" (i.e., undetected within a threshold of 40 RT-PCR cycles, by gN and gS assays, respectively). The coefficient of variation (intra-assay variation) ranged from 0.00% to 2.65% and interassay variation had an average of 2.75%. PEDV could be detected in rectal swabs from all pigs for ~2 weeks postinfection at which time the prevalence began to decrease until all pigs were RT-PCR negative by 5 weeks postinfection. Our study demonstrated that RT-PCR assays functioned well to detect PEDV and that the gN assay was slightly better.