Detection and molecular epidemiology of canine parvovirus and identification of highly pathogenic CPV-2c isolates from Shandong, China

Canine parvovirus (CPV) is an important pathogen of dogs and wild carnivores. It is a single-stranded DNA virus with a high mutation frequency and antigenic drift. To research the prevalence and genetic variation of CPV in Shandong, 62 samples from diseased dogs were collected and examined by using PCR for parvovirus. Our results showed that the positivity was 62.9% (n = 39), VP2 gene were sequenced and compared with reference strains. For the parvovirus subtype prevalence, 7 strains were CPV-2a (17.9%) and 32 strains were CPV-2c (82.1%). The results of phylogenetic analysis of VP2 gene of the CPVs showed all 39 isolates formed a major clade and were distantly related to the commercial vaccine strains. By comparing amino acid (aa) sequences, this study discovered new mutations not previously reported which may be related to host range and antigenicity. Moreover, one CPV-2c strain (QN-55) was isolated and cultured on F81 cells, and characterized by whole-genome sequencing. The TCID₅₀ of this strain was 10^–3.2/0.1 mL and animal tests have shown that the strain is fatal to infected dogs.