Phylogenetic analysis of canine parvovirus isolates from Sichuan and Gansu provinces of China in 2011.

Canine parvovirus causes serious disease in dogs. Study of the genetic variation in emerging CPV strains is important for disease control strategy. The antigenic property of CPV is connected with specific amino acid changes, mainly in the capsid protein VP2. This study was carried out to characterize VP2 gene of CPV viruses from two provinces of China in 2011. The complete VP2 genes of the CPV-positive samples were amplified and sequenced. Genetic analysis based on the VP2 genes of CPV was conducted. All of the isolates screened and sequenced in this study were typed as CPV-2a except GS-K11 strain, which was typed as CPV-2b. Sequence comparison showed nucleotide identities of 98.8-100% among CPV strains, whereas the Aa similarities were 99.6-100%. Compared with the reference strains, there are three distinctive amino acid changes at VP2 gene residue 267, 324 and 440 of the strains isolated in this study. Of the 27 strains, fourteen (51.85%) had the 267 (Phe-Tyr) and 440 (Thr-Ala) substitution, all the 27 (100%) had 324 (Tyr-Ile) substitution. Phylogenetically, all of the strains isolated in this study formed a major monophyletic cluster together with one South Korean isolate, two Thailand isolates and four Chinese former isolates.