Abstract: This work aimed at investigating the genetic evolution and pathogenicity of feline parvovirus (FPV). From 2018 to 2020, 54 fecal samples suspected of cat distemper were collected in Shandong province, and the VP2 gene was sequenced by PCR and VP2 gene cloning. In order to analyze the genetic variation, the phylogenetic tree was constructed and the amino acid sequence was deduced and compared with the vaccine strain. A strain named FPV-QDC20 was isolated and cultured on F81 cells. Its characteristics were studied by electron microscopy, indirect immunofluorescence, hemagglutination assay, TCID₅₀, complete gene sequencing and animal challenge test. VP2 gene of 16 samples was sequenced successfully, of which 15 were FPV and 1 was canine parvovirus (CPV) from cat. Phylogenetic tree construction showed that the strain in this study was in the same branch, and was closely related to the published strains in other regions of China, but far related to the European strain and the vaccine strain. Amino acid sequence analysis showed that mutations in some key sites may change host range and infectivity, which may lead to immune failure. Interestingly, the variation of conserved loci 80, 93 and 103 appeared in the QDBL2 strain, which may be related to coinfection and gene recombination of canine and feline parvovirus. The animal challenge test showed that the FPV-QDC20 strain was highly pathogenic, and the cats showed typical clinical symptoms and pathological changes, and finally died. In this study, the genetic evolution of FPV strains in China was investigated to provide reference for future disease control and vaccine research.

Key words: feline parvovirus, VP2 gene, genetic evolution, pathogenicity