Identification and molecular characterization of subgroups GI.1 and GI.2 of feline calicivirus in cats (Felis silvestris catus) from Metropolitan Region of Chile.

Feline calicivirus (FCV) is a significant pathogen in cats, characterized by high genetic diversity. Understanding the characteristics of local FCV strains is essential for developing optimal therapeutic and preventive measures. This study presents, for the first time, the epidemiology, genotypic variation, and biological characteristics of FCV strains in cats from Santiago, Chile. Oropharyngeal swabs were collected from cats with respiratory disease and one cat suspected of having virulent systemic disease (VSD) in veterinary clinics between 2016 and 2019. The FCV detection rate was 48.8 % by RT-PCR. Among FCV-positive cats, 19.0 % had been vaccinated against FCV, 71.4 % were free-roaming, and 52.4 % were less than one year old. The most frequently observed clinical signs included oral ulcers (61.9 %), stomatitis (57.1 %), and nasal discharge (42.9 %). Phylogenetic analysis revealed a high genetic diversity among Chilean FCV strains (69.45-100 % nucleotide identity) and identified two distinct subgroups within the GI genogroup, with GI.1 being predominant. Comparison of the amino acid sequences of the 5'HVR_E region showed conserved differences between these subgroups, suggesting potential variations in antigenicity, tropism, and infectivity. Moreover, the viruses analyzed in this study lacked the molecular markers previously proposed for FCV pathotypes, and the replicative efficiency of the VSD-suspected strain FCV21 was similar to the URTD-FCV strains of GI.1 and GI.2 subgroups, suggesting that not all the VSD-FCV strains would have a higher replicative efficiency than URTD-FCV strains, indicating substantial regional strain diversity. Future research will be crucial for developing more effective prevention and control strategies.