Feline calicivirus (FCV)
There are many strains of FCV, (feline calicivirus) some of which appear to cause more severe disease than others. In general, FCV usually causes milder signs than FHV, often restricted to mild nasal discharge, conjunctivitis and the development of ulcers in the mouth. Even though these ulcers can be quite large, affected animals rarely have poor appetite and are usually still quite bright.
In some cases the breeder is not aware that the kittens are ill. Though severe disease is less common than with FHV, FCV can still leave the kitten open to bacterial infection and antibiotics and nursing care are needed.
Occasionally the virus causes a dramatically different disease, so called ‘pyrexia and limping syndrome’, where kittens suddenly become lame on one or more legs and g et a high temperature. Though dramatically ill, kittens usually get better rapidly with no treatment or with painkillers.
Another disease associated with FCV infection is gingivitis – inflammation of the gums. Gingivitis is very common in the pedigree cat population and many affected cats are found to be shedding FCV.
Cats that have been infected with FCV also become carriers. However, the carrier state for FCV is rather different to that for FHV. In FCV, recovered cats shed the virus for a variable length of time, but they do so continuously. Most cats shed the virus for at least one month after infection, but by two to three months approximately half of infected cats will have stopped shedding. As time goes on, the majority of cats do eventually eliminate FCV, though some cats shed the virus for years. As shedding is continuous, it is easier to decide if a cat is a carrier by looking for the virus. It is also possible to trace a cat to see if/when it stops shedding virus and may have eliminated the infection.
However, because there are many strains of FCV, it is possible for cats to be infected several times with different strains, especially if the cat visits cat shows, seminars, studs etc. Because the disease can be mild in adults, in particular if they have met FCV before or are vaccinated, it is not always noticed that the cat is ill. An FCV strain that causes mild disease in adults though, can cause more severe problems in relatively naive kittens.
More recently a more virulent strain of FCV has been identified in the USA. This strain causes severe swelling of the face and paws and has a deleterious effect on the whole body with a high mortality rate (40%). Further investigation into this strain is currently ongoing.