Molecular Epidemiological Survey of Canine Parvovirus Circulating in China from 2014 to 2019

The global distribution of canine parvovirus (CPV-2) derived from a closely related carnivore parvovirus poses a considerable threat to the dog population. The virus is continuously undergoing genetic evolution, giving rise to several variants. To investigate the prevalence of Chinese CPV-2 strains in recent years, a total of 30 CPV-2 strains were collected from 2018 to 2021 and the VP2 gene was sequenced and analyzed. Two variants, new CPV-2a (297Ala, 426Asn) and CPV-2c (426Glu), were identified. In contrast to previous reports, the CPV-2c variant has gained an epidemiological advantage over the new CPV-2a variant in China. To compensate for the relatively small sample size, 683 Chinese CPV-2 strains identified between 2014 and 2019 were retrieved from the GenBank database and previous publications, and analyses of these strains further supported our findings, which should be considered since the CPV-2c variant has been frequently associated with immune failure in adult dogs. VP2 protein sequence analysis revealed several amino acid substitutions, including Ala5Gly, Pro13Ser, Phe267Tyr, Tyr324Ile, Gln370Arg, Thr440Ala, and Lys570Arg. Phylogenetic analysis of full-length VP2 gene indicated a close relationship between Chinese strains and other Asian strains, suggesting mutual transmission between Asian countries. Furthermore, intercontinental transmission is a cause for concern. Surprisingly, two feline panleukopenia virus (FPV) strains with the Ile101Thr mutation in the VP2 protein were identified in canine fecal samples; FPV has been considered incapable of infecting dogs. This study clarified the epidemic characteristics of Chinese CPV-2 strains detected between 2014 and 2019, offering a reference for epidemic control. In addition, the detection of FPV in canine samples may provide information for future studies on the evolution of carnivore parvoviruses.