Abstract: Porcine deltacoronavirus (PDCoV) is a newly discovered pathogenic porcine coronavirus that has been isolated from diarrheal pigs in farms of some provinces in China, confirming that the disease has been prevalent in our country. This study aims to investigate the prevalence and molecular evolution of PDCoV in Zhejiang Province. The results showed that the established PDCoV one-step TaqMan probe was specific for fluorescence quantitative detection. The detection sensitivity was 3.94 × 10² copies·μL^-1. The amplification efficiency was 108% and the R² value was 0.997, regression equation of standard curve is Y=-3.156X+1.826. The virus was not detected in clinical diarrhea samples of 258 piglests collected from April, 2013 to December, 2016, but the positive rate was 50% (12/24) in the period from January to April, 2017. The homology of the nucleotide and amino acid of the S gene of the seven clinical isolates was 99.98%-100% and 99.99%-100%, respectively. Compared with the reference strain and the Hongkong and American isolated trains, there were three base deletions and a number of mutations in our clinical isolated strains. S-protein was used for the molecular evolution analysis. Seven strains of clinical isolates were found to be belong to the evolutionary branch of the delta virus, and were closer to the other PDCoV strains isolated from China, while farther to the strains isolated from the United States and Thailand, suggesting that PDCoV epidemic strains have a certain geographical distribution. This study provides the genetic characteristics of PDCoV clinical isolates in Zhejiang Province, and provides data for the prevention and control of PDCoV-induced piglet diarrhea and the development of epidemic strains.

Key words: porcine deltacoronavirus, RT-PCR, S gene, molecular characteristics, phylogenetic analysis