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FELINE CALICIVIRUS, THE CONSTANTLY MUTATING PATHOGEN
The ABCD recommends annual boosters for high-risk cats

The European Advisory Board on Cat Diseases (ABCD) has published the first European prevention and treatment guidelines for feline calicivirus (FCV) infection.

FCV is a very common viral cause of feline oral and upper respiratory disease (‘cat flu’), and often occurs in combination with other pathogens, such as feline herpes virus (FHV-1)#.

Varied virulence and post-infection protection

"Just like the human ’flu virus, FCV is a highly variable virus and constantly mutates. Numerous strains of feline calicivirus exist – and more may come up every day,” explained Dr Alan Radford (Liverpool University), ABCD member and internationally recognised specialist on feline calicivirus.
“This is also why we see a variation in virulence and post-infection immunity.

Cats that have recovered from an FCV-associated disease probably do not have lifelong protection against further episodes of disease, particularly if caused by different strains,” Dr Radford said.

ABCD recommends that boosters should be given at three-yearly intervals for cats in low-risk situations (e.g. indoor-only cats). However, cats living in crowded high-risk conditions like shelters should be re-vaccinated every year. Please talk to your vet for a personalised risk-benefit analysis for your cat(s).

FCV: the multi-faceted cat virus

Typically, acute FCV infections cause oral ulcers (sores), upper respiratory symptoms, and a high fever. FCV can also lead to transient limping. Furthermore, FCV is found in nearly all cats with chronic inflammation of the mouth (stomatitis) or gums (gingivitis), although the exact role of FCV in this condition remains unclear.

Finally, incidents of a more severe form of FCV infection have been observed recently, both in the USA and Europe, mainly affecting adult cats and causing severe generalised symptoms. Currently available vaccines appear to provide limited protection against this particular, often fatal, form of FCV. Fortunately this form of the disease seems to be extremely rare.

FCV is mainly transmitted through direct contact with saliva, ocular and nasal discharges of infected cats. These may shed the virus for several weeks or even months, well after the clinical signs have disappeared. FCV infections are very common, especially wherever cats are kept in groups and the virus may survive outside the cat for up to a month. It is resistant to many common disinfectants, but not to bleach.

Three primary vaccinations in high-risk kittens

ABCD recommends that all healthy cats and kittens should be vaccinated against FCV for optimal protection. Kittens are particularly susceptible to the virus and should receive a primary vaccination course, with the second dose given not before the age of twelve weeks.

"In high-risk situations – wherever the disease can easily be transmitted – it may be advisable to give kittens a third dose at 16 weeks, as maternal antibodies against FCV may persist beyond twelve weeks,” Dr Radford added. This applies in particular to situations where FCV has been shown to cause disease in vaccinated kittens in the past.

For further details and downloads of the full-text veterinary ABCD Feline Calicivirus Disease Guidelines, please visit www.abcd-vets.org. These guidelines also give recommendations for specific situations, such as breeding catteries, immunocompromised cats and cats undergoing corticosteroid treatment.