Objective Feline calicivirus (FCV), feline parvovirus (FPV), and feline herpesvirus-1 (FHV-1) are common highly contagious and pathogenic pathogens. In this study, these three viruses in Guangzhou-Shenzhen region were investigated to elucidate their prevalence, genetic variations and evolutionary trends.

Method From October 2021 to June 2022, oropharyngeal, conjunctival, and anal swab samples were collected from clinically affected cats in animal hospitals, animal shelters and South China Agricultural University across Guangzhou and Shenzhen. Nucleic acids were extracted from these clinical specimens and subjected to one-step RT-PCR and conventional PCR for the detection of FCV, FPV, and FHV-1. Positive samples were further processed for gene amplification and sequencing. Nucleotide sequence similarity was analyzed using DNAStar, and phylogenetic trees were constructed with MEGA 7.0. Virus isolation was performed by inoculating FCV- and FHV-1-positive samples into Crandell-Rees feline kidney (CRFK) cells, followed by serial blind passages until cytopathic effects were observed. The isolated viral strains were then identified and characterized using PCR and electron microscopy.

Result Among the 379 symptomatic cats, the infection rates for FPV, FCV, and FHV-1 were 22.16%, 19.00%, and 3.17%, respectively. Viral positivity showed no correlation with cat gender. The highest detection rates for FCV (63.89%) and FPV (58.33%) were observed in cats aged ≤6 months, while FHV-1 infections were most prevalent (66.67%) in cats aged ≥12 months. In cats vaccinated with Felocell 3^®, FCV, FHV-1, and FPV were still detected with positive rates of 75.00%, 75.00%, and 20.24%, respectively. A total of seven FCV strains, one FHV-1 strain, and two FPV strains were successfully isolated. Genomic analysis revealed 75.0%−87.5% nucleotide similarities between the seven FCV isolates and reference strains. Phylogenetic analysis classified the seven FCV isolates into two distinct clades: GZ-1-249 and GZ-1-184 clustered within GI, while the remaining five isolates belonged to GII. The 14 FPV VP2 sequences showed 97.4%−100.0% nucleotide similarities to reference strains, and all these sequences were clustered into a major phylogenetic branch with the Felocell 3^® vaccine strain M38246.1 (FPV USA Cu4).

Conclusion The results of this study enrich the epidemiological data of FCV, FPV and FHV-1, and enhance the understanding of the local prevalent variants, which will provide crucial support for the future development and optimization of regional vaccines.