Isolation and phylogenetic analysis of feline calicivirus strains from various region of China

Abstract

Feline calicivirus (FCV) is an important feline pathogen mainly causing upper respiratory tract disease, conjunctivitis, and stomatitis, and it is classified into genotype I and genotype II. To investigate the prevalence and molecular characteristics of FCV, this study collected 337 cat swab samples from animal hospitals in different regions of China from 2019 to 2021. The positive detection rate of FCV was 29.9% (101/337) by RT-PCR. Statistical analysis showed that FCV prevalence was significantly associated with living environment (p = 0.0004), age (p = 0.031) and clinical symptoms (p = 0.00), but not with sex (p = 0.092) and breed (p = 0.171). The 26 strains of FCV were isolated using F81 cells. Phylogenetic analysis showed that 10 isolates belonged to genotype I, and 16 isolates belonged to genotype II. These 26 isolates were highly genetically diverse, of which HB7 isolate had three same virulence-related amino acid loci with VSD strains. Potential loci distinguishing different genotypes were identified from 26 isolates, suggesting the genetic relationship between different genotypes. In addition, selection pressure analysis based on capsid protein of 26 isolates revealed that the protein is under diversifying selection. This study reveals the genetic diversity of FCV and provides a reference for the screening of vaccine candidate strains and the development of vaccines with better cross-protection effects.