Molecular Characterization and Phylogenetic Analysis of Feline Calicivirus Isolated in Guangdong Province, China from 2018 to 2022

Feline calicivirus (FCV) is a common feline infectious pathogen that mainly causes upper respiratory tract disease. To investigate the prevalence of FCV in Guangdong Province in China, a total of 152 nasal and throat swabs from cats suspected of FCV infection were collected in veterinary clinics or shelters from 2018 to 2022. The positive detection rate of FCV was 28.9% (44/152) by RT-PCR. In addition, twenty FCV isolates were successfully isolated and purified. Eleven out of twenty isolates were selected for further phylogenetic analyses based on the capsid protein VP1; our results revealed that seven isolates were in genogroup I, and four were in genogroup II. Notably, according to the whole genome phylogenetic tree, FCV-SCAU-11 was in the same branch as Korean isolates, and recombination analysis revealed that the FCV-SCAU-11 isolate showed potential recombinant events between the FCV-SH isolate and FCV-GXNN03-20 isolate. Furthermore, the virus replication kinetics indicated that FCV-SCAU-10, with clinically severe symptoms in patient cats, performed a more efficient replication in vitro. In conclusion, this study revealed the genetic diversity of FCVs in Guangdong Province, providing a reference for novel vaccine candidate strains and the development of effective strategies for preventing FCV infection in cats.