What is FIV?

FIV (Feline Immunodeficiency Virus) should NOT be confused with FeLV (Feline Leukemia)--they are two very different viruses. They are often mentioned together due to the 'snap' tests carried out by vets, but they differ greatly in how they affect a cat, and its expected lifespan. FeLV is a serious risk to a cat's health and longevity, whereas FIV is not.

FIV has been associated with cats for many years, although it was only labelled as such as recently as 1986. The virus depletes the number of white blood cells, which eventually makes the cat less able to fight off infection. However, because it is such a slow acting virus many FIV positive cats can enjoy a normal lifespan with no apparent health problems resulting from the virus.

FIV is species specific. It can only be transmitted from cat to cat, not to humans or other animals.

FIV belongs to the same group as Human Immunodeficiency Virus (HIV).

How Does a Cat Catch the Virus?
The virus is present in the blood and saliva of infected cats. But, like HIV, it is a very 'fragile' virus, and cannot survive for long outside the body. It also requires a high dose to establish an infection in another cat. Therefore, it is not easily passed from cat to cat. The main route of infection is through biting, when the virus in the saliva of an infected cat is injected directly into the blood stream of the cat it bites. Conversely, a cat which bites an infected cat, is at less risk of being infected, as the virus would not be injected straight into the blood stream, although there is still an element of risk.

Cats who fight are most likely to be infected. Cat fights are most likely between entire toms and these are therefore the group most at risk. Since many feral cats are unneutered and have to compete for food, there is a higher incidence of FIV in feral cats. Transmission between cats in a group who do not fight is unlikely as the virus can only survive a very brief time outside a cat's body, and it cannot be transmitted indirectly, such as on food, feeding equipment, clothes, shoes, hands etc. (unlike the situation with feline leukemia). Recent research suggests the likelihood of cats passing on FIV to others in the same household is as low as 1-2%.

It has not been proved that the virus is transmitted sexually, although often the tom cat will hold onto the scruff of the female's neck with his teeth, so if the skin is punctured at that point, transmission is possible.

The take-home message here is to prevent fighting--make sure your cat is neutered!

Preventing Your Cat from Becoming Infected
The only guaranteed way of preventing your cat becoming infected is to never let it outside, where it might meet other cats. It's a bit like never going outside your front door just in case you get run over by a bus, basically the chances are low. The best way of helping to prevent the likelihood of infection is to make sure your cat is neutered. As well as being the most humane way of reducing the future stray population, neutering reduces the tendency to fight, or to wander.

What Are the Signs of FIV?
Signs that a cat has become infected can vary greatly, so it is not always apparent until a blood test is carried out. Often, the cat may develop raised lymph nodes around six to eight weeks after being infected, and they may have a high temperature. Sometimes diarrhea or conjunctivitis may develop, possibly lasting days or even weeks, with the cat then returning to apparent health. Other common signs are gingivitis (gum inflammation), sneezing, snuffling, a discharge from the nose or eyes, or kidney failure. The eyes or brain can be affected in a very small number of cases, resulting in changes in behavior.

The fact that the virus depletes certain of the white blood cells (T lymphocytes), in theory at least, makes the cat more susceptible to other infections, and it will find it more difficult to shake them off. This is known as 'immunosuppression' and is identical to the situation in HIV infection. However, this is purely theoretical, and in practice many cats do not have any more infections than cats which are not infected with the virus.

The commonest infection to occur in FIV positive cats is gingivitis and stomatitis (inflammation of the gums and other parts of the mouth). However, FIV is not the most common cause of gingivitis. This is common in cats which are fed on an unnatural diet of sloppy canned food. Cats which are carriers of Calici-virus (one of the cat flu viruses) frequently suffer from gingivitis, as well as lots of cats which do not carry either of these viruses.

Whatever the cause, gingivitis is treated initially with a thorough dental scale and polish plus a course of antibiotics and a steroid drug to suppress the inflammation. Various other chronic infections may also occur - conjunctivitis, diarrhea, skin and respiratory tract infections (rhinitis or bronchitis). However, these are less common, and again, respond to treatment providing it is carried on for an adequate time.

What is Their Life Expectancy?

A cat who contracts FIV will usually still have a strong immune system for several years after infection, it is only over time, that the effects of the virus may start to show, and even then, most infections can be treated with the appropriate medications. With love and good care however, many FIV+ cats can live normal lifespans. These days, it's not unusual to find FIV+ cats reaching 15 years or more.

A 10 year FIV Monitoring Project was carried out at Glasgow Veterinary School involving 26 cats and the results indicated that a higher percentage of FIV negative cats died during the period of the study than FIV positive cats, and that FIV infection did not affect the cats' life expectancy. Dr Diane D. Addie (Lecturer in Veterinary Virology, University of Glasgow) said "at least 3 studies in FIV positive cats have shown a life span equal to uninfected cats." A fourteen year study by Maureen Hutchison B.Sc, BVMS, MRCVS (veterinary adviser to the Cat Action Trust) found that FIV-positive cats are more likely to die by being killed in road accidents or to be alive and well into their twilight years than they are to die from any FIV related condition.

Knowing what we now do of the prolonged nature of the condition, euthanasia is totally inappropriate and inhumane. Being killed in a road accident is a far higher risk for a cat than FIV.

So Why the Unfounded Fears about FIV?
FIV in the stray cat population has certainly caused much of the unfounded fear surrounding the virus. It is mainly un-neutered toms, fighting over food, females or territory, who pick up and spread the virus. The stray cat has no-one to look after them, and their lifestyle means they are more likely to pick up other infections, which without treatment can escalate. When one of these gets captured and taken to a vet, suffering from any number of secondary infections, it is often too late. It is the nature of a vet's work, that they will see many more ill cats than healthy ones, when in fact, there are very many more healthy FIV cats than ill ones - they just don't need to see the vet. Indeed, many pet cats will already be FIV positive, but their owners are unaware of it due to the cat being perfectly healthy!

Testing: The FIV test routinely carried out in veterinary practices detects antibodies, which develop four to six weeks after infection, but this test is often unreliable as to whether the cat has the virus. Positive test results obtained by using this simple 'ELISA' test (sometimes called a CITE test, or 'COMBO' test,) should be confirmed by an IFA test (Immuno-Fluorescent Antibody Test) or a Western Blot, as quite often false positives can occur. Some of the ELISA tests are so inaccurate as to make the whole test meaningless, and are producing 'false positives' (due to reacting with a variety of other compounds in the cat's blood). According to the Glasgow Companion Animal Diagnostic Unit web-site (where they give the results of an on-going survey), up to 7% of positive results with the ELISA test are negative when checked by the more accurate IFA test. Many rescues have given up using the ELISA test, and are now using the IFA test only, saving time and money, while also being more accurate.

Very rarely, false negative results can occur if the test is done too early for antibodies to have developed, or simply because of the inaccuracy of the ELISA test. Again the IFA test will confirm with far more accuracy.

Treatment: Treatment consists of dealing with whatever symptoms occur in the individual cat, such as common infections being treated with Antibiotics. If an FIV positive cat displays any symptoms of illness, however minor, it should be taken to a vet promptly. Once established in a cat's cells, the virus is permanent, and no proven vaccine exists.

Adopting an FIV positive cat
A healthy FIV positive cat can live for many years, and indeed can often outlive non-infected cats, but please be aware that this is not always the case. Due to their impaired immune system, the cat may succumb to illness earlier, and not reach their normal life expectancy. FIV cats will need prompt veterinary assistance for even minor symptoms. With good care however, many FIV+ cats can live normal lifespans. These days, it's not unusual to find FIV+ cats reaching 15 years or more.

Can FIV-Positives and FIV-Negatives Live Together?

The most recent research carried out at Glasgow University's Companion Animal Diagnostics indicates that the chances of FIV being passed from one cat to another in the same household is approx 1-2%. This means that if you have 100 cats (!) in a house with 1 FIV positive cat, only 1 or 2 could be expected to become infected. Even when FIV was passed on, as in the Glasgow survey, none of the cats actually died of it. In another survey a few years ago FIV was not passed from cat to cat in the same household at all.

The Celia Hammond Animal Trust have been conducting a long-term study at their sanctuary since the late 1990's, where FIV-positive and FIV-negative cats live happily together, grooming each other and sharing food bowls and litter trays. Regular blood tests for the virus are carried out, and to date no cases of transmission have yet been found.

There seems no reason, therefore, not to have FIV positive and negative cats in the same household, provided they are not fighters. If two cats in one household fight, they should be kept apart, given behavioral therapy or one re-homed, regardless of their FIV status. So, this is obviously a decision to be taken on a case by case basis, depending on the natures of the cats involved.

Cats are far more at risk of being bitten by an unknown feral or stray FIV-positive cat
than by a friendly, neutered, FIV-positive cat living as part of the family

Should FIV+ Cats be Allowed Outside?

Some rescues insist that FIV+ cats are homed as 'indoor cats' or go to homes with an enclosed garden to prevent contact with other cats. Certainly if the cat has aggressive tendencies it should not be allowed free access to the outside world, or to mix with non-infected cats. However, being indoor-only may be considered as reducing their quality of life, since most FIV positive cats have previously been used to going outdoors. In some cases being confined indoors can even cause stress, which may further lower their immune system. However, given the length of time some FIV+ cats remain in rescues before being adopted, an indoor home is far better than staying in rescue, and will also limit their exposure to outside infections. An enclosed garden can be a good compromise.

In cities and urban areas where there are a high numbers of stray and unneutered male cats, there is little benefit in confining a neutered, cared-for, FIV positive cat indoors when a large percentage of cats outdoors will already carry the virus. However, in rural areas and where there are low rates of FIV infection, the decision on whether to allow an FIV+ cat access to the outdoors needs to be taken with a view to preventing the spread of FIV locally.

The decision then should be taken both with regard to the individual cat's nature and needs, and also as to whether the virus is already present in the general cat population in the area.

Caring for Your FIV+ Cat

Good care and lots of love can help your FIV+ cat to enjoy a long life. While healthy, their regular annual vaccinations should be kept up to date, but do check with your vet about vaccinating if the cat is suffering symptoms. A good diet will help, including vitamin supplements such as buffered vitamin C (sodium ascorbate) and vitamin E, which builds immune system strength. At any sign of illness, take your cat to the vet, as early treatment can prevent many problems. Antibiotics can control infections, and FIV+ cats who reach a chronic stage may rely on antibiotics more frequently.

Love is a Powerful Immune System Enhancer - so Cherish your FIV+ Cat!

Boarding your FIV Cat

Boarding catteries should have no problem accepting an FIV cat, since the virus cannot be transmitted by feeding equipment etc. although you should make them aware of the cat's condition. The cattery will need to know this, to ensure that they are not allowed contact with other cats, and also so that they can keep a close eye for any symptoms of illness, and act promptly.


FIV cats should always be neutered, however if a female FIV positive cat is allowed to become pregnant it is extremely rare for the kittens to become infected with the virus. FIV differs from feline leukemia in that respect, in that it is not passed on from the queen to kittens in utero. However, kittens born to an infected mother will absorb antibodies from her milk and will therefore give a positive response to the FIV antibody test. In these kittens the test becomes negative after 12-16 weeks, as their maternal immunity wanes. 

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