A SYBR Green-based real-time RT-PCR assay for simple and rapid detection and differentiation of highly pathogenic and classical type 2 porcine reproductive and respiratory syndrome virus circulating in China

SYBR Green coupled to melting curve analysis has been suggested to detect RNA viruses showing high genomic variability. Here, a SYBR Green-based real-time RT-PCR assay was developed for simultaneous detection and differentiation of highly pathogenic porcine repro- ductive and respiratory syndrome virus (HP-PRRSV) and classical type 2 PRRSV (C-PRRSV). The different strains were identified by their distinctive melting temperatures: 82.98 ± 0.25 C and 85.95 ± 0.24 C for HP-PRRSVs or 82.74 ± 0.26 C for C-PRRSVs. Specificity was tested using nine other viral and bacterial pathogens of swine. The detection limit was 1 TCID50 for HP- or C-PRRSV. Furthermore, the detection results for samples from an animal trial with HP- or C-PRRSV infections showed that the SYBR Green-based real-time RT-PCR was more sen- sitive than the conventional RT-PCR. Additionally, an analysis of 319 field samples from North China, Central China and Northeast China showed that HP- and C-PRRSVs co-circulated in pig herds. Thus, the SYBR Green-based real-time RT-PCR, which can be performed within one hour, is a rapid, sensitive and low-cost diagnostic tool for rapid differential detection and routine surveillance of HP- and classical type 2 PRRSVs in China.