Abstract
Feline calicivirus (FCV) is recognized as one of the most prevalent etiological agents of disease in
cats, distinguished by its high transmissibility and a remarkable capacity for immune evasion.Following the acute phase of infection, some cats may persist as chronic carriers or experience
recurrent cycles of infection with different or mutated strains, making them a major Clinical
manifestations of infection often include upper respiratory tract infections, oral ulcers, and
excessive salivation, in addition to gingivitis and stomatitis in other cases. In some forms, may
progress to a more severe type known as Virulent Systemic Feline Calicivirus (VSFCV), which is
associated with high mortality rates. Because of high transcription polymerase error rates in RNA
virus so it has given it a strong ability for genetic adaptation, allowing it to respond quickly to
environmental instability.This phenomena allow it to undergo severe genetic and antigenic
diversity, leaning in the develoment of new variants that complicate the process of controlling it
later. FCV is associated with a wide range of clinical signs, starting from asymptomatic infections
and relatively mild oral and respiratory illnesses to severe lameness with or without systemic
infections with high mortality rate.It is worth noting that a percentage of cats that recover from
acute infection remain infected with chronic infection,and it is believed that continues evolution
of the virus within these animals helps it evade the host immune response. Although these chronic
cases may represent a minority, they play a pivotal role in the epidemiology and spread of the
virus.