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Feline calicivirus (new strains)

ISSN 2398-2950

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Synonym(s): Virulent systemic disease, VSD strains




  • Family: Caliciviridae.
  • Genus: Vesivirus.



  • Highly contagious; stable in the environment in the short term.
  • Can persist for up to several weeks in a contaminated environment.
  • Pneumotropic strains causing interstitial pneumonia Pneumonia are highly virulent.
  • More recently recognized strains associated with a virulent systemic disease (FCV associated VSD).
  • FCV associated VSD causes significant mortality (approximately 50% in a group of cats) even in vaccinated cats.

Active Forms

Active Form 1

  • Feline Calicivirus 1.



  • Caliciviridae Family, Genus Vesivirus.


Temperature Other
  • Resistant to many disinfectants; not susceptible to detergents such as quaternary ammonium compounds; requires oxidizing agent for disinfection such as hypochlorite (bleach) at 1:32 in water.
  • Must first remove all organic material (eg discharge, feces, etc) from cage, bowls, etc for disinfection to be effective.


  • Virus is shed by "carrier" cats during persistent infection; no latency occurs.

Resting Forms

Clinical Effects



  • Epithelium of respiratory tract, oral cavity, conjunctiva; virulent systemic strains may have tropism for other cells including vascular endothelium and hepatic cells.


  • Many clinically recovered cats become carriers of feline calicivirus.
  • Carriers shed virus more or less continuously from the oropharynx.
  • The number of cats in the population who are carriers is reasonably high and prevalence depends on the husbandry conditions of the cat; multi-cat colonies can have a prevalence of FCV of up to 90% (see feline calicivirus Feline calicivirus).


  • Fomites very important in spread of the virus; shed in respiratory secretions.

Pathological effects

  • Virulent systemic strains are associated with subcutaneous edema, hemorrhages; epithelial necrosis, including crusting of pinna, face; fluid in abdominal and thoracic cavities (~100 ml); necrotizing hepatitis; pancreatitis; interstitial pneumonia; lesions may be found in intestinal crypts.
  • More severe disease reported in adults vs. kittens for the virulent systemic strains, similar to rabbit hemorrhagic disease, caused by a calicivirus of rabbits.

Other host effects

  • Typical signs include fever, facial or limb edema or sores, alopecia and ulceration of face or feet and jaundice.


Control via animal

  • Strict isolation of affected animals; isolate shelter/rescue cats for 1-2 weeks before introducing to other cats.
  • Affected cats should be barrier nursed; staff nursing these cats should preferably have no cats at home to prevent infection of their own animals.
  • All cats from affected households should be kept indoors to prevent spread of the virus.

Control via chemotherapies

  • Interferon Interferon has been used to treat some cats with virulent systemic disease although there are no published reports of the efficacy of this treatment and it is not licensed for this use. Anecdotal reports suggest there has been some improvement seen in a few affected cats following treatment.
  • Anecdotal information indicates corticosteroids may be helpful in acute disease.

Control via environment

  • Most common in multicat environments; outbreaks reported in veterinary clinics; strict isolation of any suspected infected cats paramount.
  • Fomites, including clinic personnel/owners/etc are very important in spread; good disinfection and hygiene important to minimize spread.


  • Due to strain variation, coverage of protection with vaccines containing single strains may be incomplete.
  • Experimentally some vaccines have been found to give some protection against the virulent systemic strains although in field cases many of the affected cats have been vaccinated.


Useful samples

  • Virus isolation remains the gold standard this can be done from orpharyngeal swabs or tissue samples. Epithelial cells collected from lesions or oropharyngeal region using swabs applied to glass slides for antigen detection or alternatively the swabs may be used for genetic detection by PCR PCR (Polymerase chain reaction).
  • PCR has been found to be less sensitive than virus isolation for FCV; this is probably due to the large strain variability within these viruses.

Specimen storage

  • Glass slides need no special storage; swabs for PCR should be refrigerated not frozen; samples for virus isolation should be refrigerated or frozen and sent in virus transport medium.

Transport of samples

  • Swabs for PCR and samples for virus isolation should be shipped on cold pack. Samples for virus isolation should be sent in viral transport medium which can be supplied by the laboratory to which you are sending the sample.


  • Virus isolation can be carried out in feline cell lines at appropriate laboratories.
    It must be remembered when interpreting results that many cats can be carriers of feline calicivirus and therefore isolation of the virus may not necessarily be associated with current disease in the cat.

Field diagnosis

  • Lesions/clinical signs; for virulent systemic strains, subcutaneous edema, crusting skin lesions with respiratory signs; necrotizing lesions involving liver, pancreas, intestines; interstitial pneumonia; jaundice.
  • History of contact with other affected cats or cats from a rescue shelter.

Laboratory diagnosis

  • In addition to paired serology, antigen detection and virus isolation, PCR for genetic detection can be used; false negative results with PCR can occur due to strain variation.
  • Typing of feline calicivirus isolates can be carried out although there does not appear to be one specific strain associated with virulent systemic disease; several different strains have so far been identified.

Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • 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.
  • Foley J, Hurley K, Pesavento P A et al (2006) Virulent systemic feline calicivirus infection: local cytokine modulation and contribution of viral mutants. J Feline Med Surg 8 (1), 55-61 PubMed.
  • Hurley K E, Pesavento P A, Pedersen N C et al (2004) An outbreak of virulent systemic feline calicivirus disease. JAVMA 224 (2), 241-249 PubMed.
  • Pedersen N C, Elliot J B, Glasgow A et al (2000) An isolated epizootic of hemorrhagic-like fever in cats caused by a novel and highly virulent strain of feline calicivirus. Vet Microbiol 73 (4), 281-300 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.
  • Kreutz L C, Johnson R P & Seal B S (1998) Phenotypic and genotypic variation of feline calicivirus during persistent infection of cats. Vet Microbiol 59 (2-3), 229-236 PubMed.
  • Baulch-Brown C, Love D N & Meanger J (1997) Feline calicivirus: a need for vaccine modification? Aust Vet J 75 (3), 209-213 PubMed.
  • TerWee J, Lauritzen A Y, Sabara M et al (1997) Comparison of the primary signs induced by experimental exposure to either a pneumotrophic or a 'limping' strain of feline calicivirus. Vet Microbiol 56 (1-2), 33-45 PubMed.
  • Turnquist S E & Ostlund E (1997) Calicivirus outbreak with high mortality in a Missouri feline colony. J Vet Diag Invest (2), 195-198 PubMed.