Felis ISSN 2398-2950

Feline calicivirus

Synonym(s): FCV, picornavirus, cat flu virus, Manx virus

Contributor(s): Karen Coyne, Susan Dawson, Melissa Kennedy, Alan Radford




  • Family: caliciviruses.


  • Greek: calyx means cup, calicivirus has many cup-shaped subunits on its surface as seen by electronmicroscopy.

Active Forms

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Clinical Effects



  • Stratified squamous epithelial cells of the tongue, pharynx, tonsil and nostril.


  • Usually direct, cat to cat.
  • Aerosol, only up to a few feet (1 m).
  • Indirect transmission may occur via fomites eg feedbowls, utensils, bedding or via personnel.

Pathological effects

  • Antigenic variation occurs such that neutralizing antibodies to one strain may not neutralize all other strains.
  • Vaccine strains are chosen as they are broadly cross-reactive and will neutralize a high percentage of strains.

Other Host Effects

  • Continuous virus shedding occurs in carrier animals.
  • Carrier animals are classified as cats who shed virus for 30 days or more post-infection; carrier cats usually 'self-cure' several months after infection but some persist lifelong.
    FIV positive cats are more likely to become persistent carriers.
  • Some cats can eliminate the virus but become reinfected with either a different strain of FCV, or a variant of the same strain.
  • It is therefore thought that some cats undergo cyclical re-infection, particularly in large groups of cats, where the prevalence is relatively high.


Control via chemotherapies

  • No anti-viral drugs in use.
  • Supportive: broad spectrum antibiotics to deal with secondary bacterial infection, multivitamins.
  • Oxygen for those with pneumonia - can be difference between life and death.

Control via environment

  • Bleach diluted 1:32 in water with washing-up liquid is recommended. Detergents like quartenary ammonium not effective.


  • Attenuated living and inactivated systemic vaccines available.
  • 2 doses given at 8 and 12 weeks, or 2-4 weeks apart.
  • 6 monthly or yearly boosters or three yearly boosters.
  • Vaccination prevents or reduces disease but does not prevent infection.
  • Vaccination will not work in kittens already incubating the disease and many so-called vaccine reactions are, in fact, where this has occurred.
    Avoid aerosolizing (or nasal contact) systemic vaccines - if taken oronasally, these may cause clinical disease.
  • Vaccination does not eliminate virus from cats who are already carriers.

Other countermeasures

  • Treatment for cat flu:
    • Mucolytics.
    • Eucalyptus oil on bedding or bandana or steam inhalation to aid clearing of nasal passages.
    • Good nursing essential.
    • Use strong-smelling foods, eg sardines, to encourage cat to eat.
  • Treatment for gingivitis Gingivitis and stomatitis:
    • Oral hygiene: de-scaling, tooth brushing.
  • FCV prevention in kittens:
    • Boost queen's immunity before conception.
    • Isolate queen from other cats before birth of kittens.
    • Ensure good intake of colostrum to supply maternally derived immunity.
    • Wean kittens early, at 2-3 weeks of age, and keep isolated from other cats.
    • Vaccinate systemically at 8 and 12 weeks of age.
    • Early vaccines have been used but are not licensed.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Porter C J, Radford A D, Gaskell R M et al (2008) Comparison of the ability of feline calicivirus (FCV) vaccines to neutralise a panel of current UK FCV isolates. J Feline Med Surg 10 (1), 32-40 PubMed.
  • Radford A D, Coyne K P, Dawson S et al (2007) Feline calicivirus. Vet Res 38 (2), 319-335 PubMed.
  • Coyne K P, Dawson S, Radford A D et al (2006) Long-term analysis of feline calicivirus prevalence and viral shedding patterns in naturally infected colonies of domestic cats. Vet Microbiol 118 (1-2), 12-25 PubMed.
  • Coyne K P, Jones B R, Kipar A et al (2006) Lethal outbreak of disease associated with feline calicivirus infection in cats. Vet Rec 158 (16), 544-550 PubMed.
  • Schorr-Evans E M, Poland A, Johnson W E et al (2003) An epizootic of highly virulent feline calicivirus disease in a hospital setting in New England. J Feline Med Surg (4), 217-226 PubMed.
  • Dawson S, Willoughby K, Gaskell R M et al (2001) A field trail to assess the effect of vaccination against feline herpesvirus, feline calicivirus and feline panleucopenia virus in 6-week-old kittens. JFMS (1), 17-22 PubMed.
  • Radford A D, Sommerville L M, Dawson S et al (2001) Molecular analysis of isolates of feline calicivirus from a population of cats in a rescue shelter. Vet Rec 149 (16), 477-481 PubMed.
  • Binns S H, Dawson S, Speakman A J et al (2000) A study of feline upper respiratory tract disease with reference to prevalence and risk factors for infection with feline calicivirus and feline herpesvirus. JFMS (3), 123-133 PubMed.
  • Radford A D, Dawson S, Wharmby C et al (2000) Comparison of serological and sequence-based methods for typing feline calicivirus isolates from vaccine failures. Vet Rec 146 (5), 117-123 PubMed.
  • Dawson S & Willoughby K (1999) Feline infectious upper respiratory tract disease - an update. In Practice 21 (5), 232-237 VetMedResource.
  • Dawson S, Gaskell R & Jarrett O S (1999) Vaccination in cats - an update. In Pract 21 (2), 71-74 VetMedResource.
  • Radford A D, Bennett M, McArdle F et al (1999) Quasispecies evolution of a hypervariable region of the feline calicivirus capsid gene in cell culture and persistently infected cats. Vet Microbiol 69 (1-2), 67-68 PubMed.
  • Thiel H J, König M (1999) Caliciviruses - an overview. Vet Microbiol 69 (1-2), 55-62 PubMed.
  • van Vuuren M, Geissler K, Gerber D et al (1999) Characterisation of a potentially abortigenic strain of feline calicivirus isolated from a domestic cat. Vet Rec 144 (23), 636-638 PubMed.

Other sources of information

  • Gaskell R M & Dawson S (1994) Viral-induced upper respiratory tract disease. In: Feline Medicine and Therapeutics .Ed. Chandler E A, Gaskell C J & Gaskell R M. Blackwell Science, Oxford OX2 0EL, UK. pp 453-472.
  • Gaskell R M & Bennet (1996) Feline infectious respiratory disease. In: Feline and Canine Infectious diseases.Blackwell Science, Oxford OX2 0EL, UK. pp 3-28.