Development and evaluation of a duplex real-time RT-PCR for detection and differentiation of virulent and variant strains of porcine epidemic diarrhea viruses from the United States

Porcine epidemic diarrhea virus (PEDV) has caused significant economic losses in the US swine industry since May 2013. A new variant strain of PEDV emerged in the US in the late December, 2013. This variant strain of PEDV differs from the virulent strain of PEDV currently circulating in the US in 1170 nt of the 5'end of the S1 domain in the spike gene. Importantly, the variant PEDV caused significantly less mortality in piglets than the virulent PEDV, based on clinical observations. This suggests it may be a potential vaccine candidate for PED. Variant PEDV has been detected in samples from multiple states by our laboratory as well as other laboratories in the US. It is critical to detect and differentiate variant PEDV from the virulent PEDV during outbreaks to enhance control and to prevent PED associated disease. In this study, the development and validation of a duplex real-time RT-PCR assay for detection and differentiation of the variant and the virulent strains of PEDV currently circulating in the US was reported.