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Feline Calicivirus

Facts About Calicivirus Infections in Cats


feline calicivirus (FCV), a Caliciviridae family member by Joel Mills/CDC.

Feline calicivirus (FCV), a Caliciviridae family member

by Joel Mills/CDC.

About Feline Calicivirus

  • A common virus affecting cats (other caliciviruses infect other species)
  • The "C" in "FVRCP" combination (three-in-one) vaccines stands for calicivrus.
  • There are several different strains of calicivirus
  • Caliciviruses are most often associated with upper respiratory infections ("colds") in cats
  • Calicivirus infections may occur in combination with other viruses or bacteria to produce more severe upper respiratory infections
  • Illness due to calicivirus varies in severity
  • Some feline calicivirus strains cause limping due to arthritis
  • Rare, but particularly virulent, strains of feline calicivirus cause a very severe and often fatal illness
  • Cats with calicivirus can remain infected for a very long time after the symptoms resolve (sometimes a lifetime), and can act as a source of infection for other cats.

Diseases Associated with Calicivirus in Cats
Causes upper respiratory infections, either alone or in combination with other viruses or bacteria. Signs such as discharge from the eyes and nose, sores in the mouth, fever, loss of appetite and lethargy are common. Sometimes limping may be seen, and some cases result in pneumonia. You can read more about upper respiratory infections here.

A rare, severe form of feline calicivirus has also been seen, which produces very severe illness affecting multiple body systems ("systemic illness"). Isolated outbreaks have cropped up in recent years, typically in situations where many cats are housed together (like shelters). This form has been called virulent systemic feline calicivirus (VS-FCV), and the syndrome it causes has been called virulent systemic disease (VSD) or hemorrhagic calicivirus. This form is very contagious and is quite often fatal. Any of the following signs may be seen along with an upper respiratory infection: fluid build up (edema) in the skin, sores on the skin, vomiting, diarrhea, jaundice, and signs of pneumonia.

Calicivirus infections are also almost always found in cats with chronic inflammation of the mouth and gums (stomatitis / gingivitis). However, it is unclear what role, if any, calicivirus has in the development of this disease.

Risk Factors
Kittens are most at risk of becoming ill with calicivirus, along with unvaccinated cats and cats with weakened immune systems (e.g., FeLV or FIV positive cats, or those ill from other things).

Different vaccines are available; some are given by injection (often in combination vaccines) while others are given in the nose. Your vet can help you choose the right type of vaccine and schedule for your cat. Calicivirus strains are so variable that the vaccines do protect equally against all strains, so some vaccinated cats may still experience mild illness. Vaccinated cats can still become carriers of the virus. A special vaccine is now available for the severe form of calicivirus (VS-FCV), and your vet can discuss if this vaccine is right for your cat.

Incubation Period
Signs and symptoms can appear within a couple of days to a couple of weeks after exposure to the virus.

Survival in Environment
Estimates range from ten days to four weeks under typical conditions.

Resistant to many disinfectants. A 1:32 dilution of bleach (one part bleach to 32 parts water) is considered effective at killing the virus.

Please note: this article has been provided for informational purposes only. If your pet is showing any signs of illness, please consult a veterinarian as quickly as possible.

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