Cat Feline Calicivirus: Respiratory Disease and Virulent Strains

Feline calicivirus causes upper respiratory disease in cats, with virulent systemic strains causing severe multi-organ disease with high mortality in outbreaks.

Key Facts

Calicivirus is one of the two most important upper respiratory viruses in cats alongside herpesvirus
Standard FCV causes mild to moderate upper respiratory signs with oral ulceration
Virulent systemic FCV strains cause severe facial oedema, skin ulceration and systemic organ failure
VS-FCV outbreaks in shelters and catteries have mortality rates of 30-50% even with intensive care
Current vaccines do not reliably protect against VS-FCV strains as antigenic diversity is high
Vaccination reduces severity of disease from standard strains but does not prevent all infection
Contact tracing and isolation are essential when VS-FCV is suspected in multi-cat environments

Welfare Considerations

Standard FCV causes oral ulcers that make eating extremely painful - affected cats often drool, paw at their mouths and refuse food despite hunger, causing rapid weight loss that compounds their illness. Virulent systemic FCV causes one of the most rapid and severe disease progressions seen in companion animal medicine - cats in apparently good health can deteriorate to critical condition within 24-48 hours of outbreak. The high mortality even with intensive care reflects both the virulence of these strains and the severity of multi-organ involvement. Shelter and cattery outbreaks can be devastating, causing simultaneous suffering in multiple animals.

What You Can Do

Vaccinate all cats against calicivirus as part of the core vaccination programme
Isolate any cat showing signs of upper respiratory disease immediately from other cats
Seek emergency veterinary care for any rapidly deteriorating cat during a suspected calicivirus outbreak
Implement strict hygiene protocols in multi-cat environments to limit virus spread
Report suspected VS-FCV outbreaks to your vet and public health authorities immediately
Support shelters with robust isolation facilities that can contain respiratory outbreaks
Provide supportive care including appetite stimulants and soft food during recovery from oral ulcers