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Feline Immuno Deficiency Virus was first identified in a cat rescue centre in the USA where cats were showing signs similar to people with AIDs. Analysis of stored samples in the UK show that it has been present in this country since at least the 1960s. About 3-6% of the UK cat population has the disease although it is more common in feral cats.

How is it spread?

The first thing to say is that although FIV is a very similar to HIV it cannot be spread to people, just as HIV cannot spread to other species. Infected cats have lots of virus in their saliva although the virus only survives a few hours outside of the body.

Fighting between cats is the main mode of transmission, so it tends to be most common in entire male cats living outside who tend to get into the odd scrape!

However any age, or type, of cat can get attacked and develop the disease. Although now thought to be a rare occurance, it is also possible for spread to occur via sharing food bowls, mutual grooming and from queens to kittens.

Signs and Symptoms

Initial infection with FIV tends to produce a short-lived mild illness which may go unnoticed. The cat may stop eating and have a high temperature for a few days. The disease then enters an intermediate stage where the cat will appear completely healthy although, like HIV, it will be infectious to other cats. This stage can last many years and, in fact, many cats may not get sick at all.

In the final stage, the virus starts to damage various tissues in the body causing varying signs. Most commonly the immune system is damaged leading to “immuno deficiency” (an ability to deal with infections and tumours normally). Typical signs include fever, weight loss, inflammation of the gums, chronic abcesses, diarrhoea, sneezing, conjunctivitis and an increases risk of developing cancer. If it attacks the nervous system then behavioural changes, fitting and blindness can occur. It can even just attack the feet causing soft pads!


If there is a suspicion that your cat may be suffering from FIV then a blood test is usually performed at the practice using a special kit. If this is positive then it is usually best to send another sample off to an outside laboratory for confirmation.


Unfortunately there is no specific treatment to cure or control the disease fully. Several different treatments have been tried with varying success. The human HIV drug, AZT, appears to be the most effective. However it can cause side effects such as anaemia, so regular blood tests are required during treatment. Interferons can help but are very expensive. Evening primrose oil has given a mild improvement in the early stages.

Management of FIV cats

As these cats have a failing immune system, it is very important to identify and treat any secondary infections that the cat picks up. Twice yearly check ups at the vet are a good idea to look for infections. In particular the mouth, chest and abdomen should be examined and blood and urine samples taken for monitoring.

The biggest factor in maintaining health tends to be keeping FIV cats inside where they are unlikely to get into fights, pick up flu or get infected with worms, fleas and other parasites. The other reason to keep FIV cats inside is to prevent them infecting other cats in the area – something we are sure your neighbours would appreciate.

FIV certainly need not be a death sentence for your cat. If the cat steers clear of infections by staying inside and is regularly checked, there is every chance that he/she could live a completely normal life span, as happy as any other cat.

What about my other cats?

One question is what to do if you have other cats in the household. Fortunately it is rare for FIV to spread between cats in the same household except through fighting.

Our advice would be to test all the other cats in the house so they can be treated and monitored accordingly.

Ideally FIV positive cats should be kept separate from negative ones. However, if your cats have been together for a while and they all get on well together then it should be fine to continue as before. What is not advisable is to introduce new cats into the house which might upset the feline hierarchy and start off bouts of fighting.


There is no vaccine available against FIV in the UK. One has recently been introduced in the USA although there are concerns over its effectiveness. Worldwide there are several strains of FIV and the vaccine only works against one or two of them. The other problem is that on current blood tests cats that are vaccinated against the disease show a positive result. Therefore it is impossible to differentiate between a vaccinated and an infected cat. It then becomes difficult to know what to do with a FIV vaccinated cat showing signs of FIV!

What about other vaccinations for an FIV positive cat?

Logically one would think that vaccinating would be a good idea to prevent infections. However, researchers have found that stimulation of the immune system can make FIV worse. Generally, our advice would be to vaccinate FIV cats that go outside (although we strongly recommend keeping your cat in) against Cat Flu, Enteritis and Leukaemia.

Cats that live indoors but share a household with free roaming cats should ideally be vaccinated against Cat Flu and Enteritis. Indoor FIV positive cats which are kept by themselves should not be vaccinated. Although this all seems a bit complicated it is the best solution to a subject with no set rules.

In conclusion FIV is a serious disease for cats but fortunately not for humans. Although unpleasant and incurable, the symptoms often are controllable with the right monitoring and treatment. In fact, in a recent study of 20 cats kept in a house, half FIV positive, half FIV negative, the FIV positive cats actually lived longer than the negative ones! There was also no transmission between the two groups of cats.