A divergent canine parvovirus type 2c (CPV-2c) isolate circulating in China.

The variability and the intrinsically high mutation rate of canine parvovirus type 2(CPV-2) increased the diversity of CPV-2 in canine populations. Since the first occurrence of CPV-2, three antigenic variants (2a, 2b and 2c) were detected and distributed worldwide. CPV-2c infection has been detected and increasingly reported in China. Here, a CPV-2c strain CPV-SH1516 was isolated and its complete genome sequence was first characterized. Compared with other CPV-2c isolates, CPV-2c isolates from China continued to evolve into divergent CPV-2c variants with specific unique amino acid substitutions under purifying selection. Emergence of CPV-2c isolates from China was driven by the unique gradual point mutations in key sites of VP2 rather than introduction from outside China. Combining sequence comparison with phylogenetic analysis based on the amino acid sequences of VP2, the vast majority of CPV-2c isolates from China formed a monophyletic cluster and CPV-SH1516 was a representative isolate of CPV-2c circulating in China. Overall, our study provides valuable insight into the evolutionary mechanism of CPV-2c.