Submitted to: Journal of Veterinary Diagnostic Investigation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/4/2015
Publication Date: 1/27/2016
Citation: Miller, L.C., Crawford, K.K., Lager, K.M., Kellner, S.G., Brockmeier, S. 2016. Evaluation of two real-time polymerase chain reaction assays for porcine epidemic diarrhea virus (PEDV) to assess PEDV transmission in growing pigs. Journal of Veterinary Diagnostic Investigation. 28(1):20-29.
Interpretive Summary: Porcine epidemic diarrhea virus (PEDV) was first diagnosed in the United States in April 2013 as sporadic cases of diarrhea in young piglets resulting in high mortality A study was conducted to assess the transmission potential of young pigs experimentally-infected or experimentally-exposed to PEDV. A critical need for the current PEDV surveillance program is the rapid detection of PEDV. For this reason, a real-time PCR assay was developed and evaluated for its capability in the detection of PEDV. The aim of the present study was to evaluate the real-time PCR assay for use as a diagnostic assay to detect an acute PEDV infection and transmission in experimentally infected growing pigs.
Technical Abstract: In April 2013 a porcine epidemic diarrhea virus (PEDV) epidemic began in the United States. As part of the response, real-time RT-PCR assays to detect PEDV were developed by several Veterinary Diagnostic Laboratories. This study evaluated RT-PCR PEDV assays that detect the N gene (gN) and S gene (gS) for their ability to detect PEDV infection and transmission potential of pigs experimentally-exposed to PEDV. Detection limits and threshold cycle (Ct) values of real-time RT-PCR were assayed for PEDV samples and positive controls for both gN and gS. Following recommended guidelines, rectal swabs (n=1064) were tested; 354 samples were positive by gN assay and 349 samples were positive by gS assay (Ct=34.99), 710 samples were negative by gN assay and 715 were negative by gS assay (Ct>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 determined based on the replicates (intra-assay variation) ranged from 0.00% to 2.65% and inter-assay variation had an average of 2.75%. PEDV could be detected in rectal swabs from all pigs for about 2 weeks post-infection at which time the incidence began to decrease until all pigs were RT-PCR negative by 5 weeks post-infection. This study demonstrated the RT-PCR assays functioned well to detect PEDV and the gN assay was slightly better.