Porcine deltacoronavirus: Overview of infection dynamics, diagnostic methods, prevalence and genetic evolution.

Porcine deltacoronavirus (PDCoV) was first reported in Hong Kong, China in 2012 and reported in United States swine in February 2014. PDCoV has subsequently been detected in South Korea, mainland China, and Thailand. PDCoV has been experimentally confirmed to cause diarrhea in inoculated pigs and need to be differentially diagnosed from porcine epidemic diarrhea virus and transmissible gastroenteritis virus in the field. Rapid diagnosis is critical for the implementation of efficient control strategies against PDCoV. Developing high-quality diagnostic methods and understanding PDCoV infection dynamics to collect appropriate specimens at the appropriate time window are important to obtain reliable diagnostic results. Among the virological methods, PDCoV-specific RT-PCR remains the method of choice for the detection of PDCoV; immunohistochemistry combined with hematoxylin and eosin staining has also been commonly used to examine histopathological lesions caused by PDCoV. Serological assays can provide information about previous exposure to PDCoV and also determine antibody responses to infection or vaccination. Prevalence of PDCoV is lower compared to that of PEDV. However, among PDCoV-positive samples, co-infection with other enteric pathogen e.g. PEDV is common. It is also important to understand molecular epidemiology of PDCoV and genetic relationships of global PDCoVs. This review discusses PDCoV infection dynamics and appropriate sample collection for diagnostic testing, the commonly used virological and serological methods for PDCoV diagnosis, prevalence and genetic evolution of PDCoVs.