Description
Feline calicivirus (FCV) is a highly contagious RNA virus causing upper respiratory and oral disease in cats, with variable virulence from mild self-limiting cases to severe systemic outbreaks. Clinical signs typically include sneezing, nasal/ocular discharge (serous to purulent), hypersalivation, oral ulceration (especially on tongue, hard palate), anorexia due to painful stomatitis, and conjunctivitis; lameness from synovitis or vasculitis occurs in some strains, while virulent systemic FCV (VS-FCV) presents with severe facial/footpad oedema, ulceration, high fever, icterus, pneumonia, hepatic necrosis, and high mortality (up to 50%) in multi-cat settings like shelters.
Diagnosis relies on clinical signs in unvaccinated or exposed cats, with supportive CBC showing neutrophilia/lymphopenia and imaging for pneumonia. Samples include oropharyngeal/conjunctival swabs (in viral transport medium), nasal swabs, or postmortem tissues (lung, tonsil) for virus isolation or antigen detection (IFA/ELISA); serum for serology is less useful due to ubiquitous exposure.
Quantitative PCR (qPCR) on swabs or tissues detects and quantifies FCV RNA with high sensitivity, confirms active shedding in carriers (lifelong intermittent shedders), and monitors outbreaks or antiviral therapy response, though positive qPCR alone requires correlation with clinical signs as subclinical carriers are common.
