Distribution and genetic diversity of Feline calicivirus in Moscow metropolitan area

Feline calicivirus (FCV) is widespread throughout the world. An FCV infection is associated with conjunctivitis, rhinitis, and mouth ulcers that can lead to the animal's death. Because vaccination is not always effective, it is necessary to monitor the infection regularly.

This study examined the FCV epizootic situation in the Moscow metropolitan area by conducting a molecular phylogenetic analysis of the virus isolates.

Samples from 6213 animals were examined by a reverse transcription polymerase chain reaction. For phylogenetic analysis, 12 nucleotide sequences obtained from animal samples were selected. Sequencing was performed using the Sanger method. Phylogenetic analysis was conducted using the Maximum Likelihood method.

The FCV genome was detected in 1,596 (25.7%) samples out of 6,213. In 2018, calicivirus was detected in 18.9% of samples, 27.8% in 2019, 21.4% in 2020, and 32.6% in 2021. Phylogenetic analysis of the F ORF2 region and the ORF3 start region led to division into two FCV genogroups. Most of the isolates (8 out of 12) were close to the Chinese strains. On the other hand, there were isolates closely related to European and American strains. The isolates circulating in Moscow were not included in clusters with vaccine strains; their nucleotide similarity varied from 77% to 83%.

This study revealed a high prevalence and genetic diversity of the FCV in Moscow. The epizootic situation remains stably tense because 24 viruses were detected in 25% of animals annually.