Feline Calicivirus: An Emerging Companion Animal RNA Virus and Its Implications for Genomic Surveillance, Outbreak Preparedness, and One Health

Feline calicivirus (FCV) is a genetically diverse and rapidly evolving positive-sense RNA virus that remains a major cause of infectious disease in domestic cats worldwide. FCV is classically associated with upper respiratory tract disease and oral ulceration; however, the emergence of highly virulent systemic FCV (VS-FCV) strains has expanded its clinical significance owing to severe multisystemic disease, increased mortality, and frequent outbreaks in shelters, breeding colonies, and veterinary healthcare facilities. Continuous viral evolution driven by mutation, recombination, and immune selection promotes antigenic diversity, prolonged asymptomatic shedding, vaccine escape, and the emergence of novel variants, thereby complicating diagnosis, prevention, and disease control. This review summarizes recent advances in FCV molecular biology, viral evolution, host–virus interactions, pathogenesis, epidemiology, clinical manifestations, diagnostics, vaccination, and emerging antiviral and immunomodulatory therapies. The review also examines the available epidemiological evidence on FCV in India, highlighting reported regional findings, limitations in geographic and genomic coverage, and the need for coordinated surveillance. Within a One Health framework, FCV is considered primarily as an important companion-animal pathogen and a model for strengthening veterinary surveillance, biosecurity, genomic monitoring, and outbreak preparedness, rather than as a confirmed zoonotic threat. By integrating current scientific evidence with identified surveillance and research gaps, this review outlines priorities for improving FCV surveillance, prevention, and control and for strengthening preparedness for emerging companion-animal viral diseases.