Feline Immunodeficiency Virus (FIV)

What is Feline Immunodeficiency Virus (FIV)?

FIV was first documented in 1987, although evidence for FIV infected cats can be traced back to the late 1960s. It is a condition similar to the HIV (human immunodeficiency-) virus that causes AIDS in humans, but there is no risk of humans catching FIV or FAIDS from infected cats.

Both FIV & HIV belong to a class of viruses known as lentiviruses, meaning that they progress very slowly, gradually affecting the carrier's immune system. In order to fight infections and monitor for cancers in the body, you need a healthy immune system. FIV suppresses the immune system by infecting the white blood cells, killing or damaging them. Hence, FIV infected cats are at a greater risk of disease and infection from other viruses and bacteria - both in terms of catching them and subsequently fighting them.

FIV is a fatal disease and there is currently no vaccination available.

How is FIV transmitted?

Humans CANNOT 'catch' FIV - it can't be transmitted to humans or dogs, it cannot cross the species barrier. Although FIV occurs throughout the world, it is more prevalent in certain geographic areas.

FIV is not easily passed between cats. It cannot be spread casually - like in a litter tray, water or food bowls, or by cuddling or playing together, because the virus cannot survive outside of the body. It can be spread via blood transfusions, badly infected gums or - and most commonly - deep, penetrating bite wounds, the sort that occur during fighting or mating.

This is why neutering is so important for halting the spread of disease. An un-neutered male (tom) cat will roam up to 7 miles in search of females. By roaming such distances, they inevitably cross the territorities of other male cats. Territorial disputes are a primary cause of fighting among cats and, as a result of the deep, penetrative bites common in such fights, are also the primary cause of the spread of diseases such as FIV and Feline Leukaemia Virus (FeLV).

During mating, the male cat bites the female on the back of the neck to pin her down. This bite can easily transmit disease such as FIV or FeLV. Spayed females will not attract tom cats, thereby protecting against disease transmission.

FIV and other such diseases are therefore more commonly found in un-neutered male cats (particularly strays and ferals), since these cats are more likely to fight than neutered males or (spayed or un-spayed) female cats.

The disease can also, although less commonly, be transmitted by an infected queen to her kittens, either while in the womb or via her milk while nursing.

Because transmission is difficult, unless your cats at home routinely tear each other to pieces, having FIV infected and healthy cats living together isn't a problem. (And frankly, if your cats do routinely tear each other to pieces, you probably have a bigger problem on your hands!)

What are the symptoms?

The symptoms following infection with FIV are usually mild. The virus is carried to regional lymph nodes, where it replicates in the white blood cells. It then spreads to lymph nodes throughout the body, causing a general enlargement of the nodes. Unless the nodes are greatly enlarged, this stage of the illness usually passes by unnoticed by the owner.

Sometime later, possibly days but usually weeks to months, the cat may develop a mild fever, accompanied by a temporary drop in the white blood cell count. Anaemia (low red blood cell count) also may occur. The cause for these drops in blood cell counts is unknown.

The majority of cats will produce antibodies to FIV, usually within 2 - 8 weeks following infection. However, for reasons not yet fully understood, these antibodies cannot fight off the infection. The lymph nodes often become diseased, followed by a short-lived fever. The lymph nodes may remain swollen for approx 3 - 6 months. After this time, the cat may appear to be perfectly healthy and it can be months or even years before symptoms of the disease finally present. However, during this period of apparent health, progressive degenerative changes are occurring within the cat's immune system. These will eventually compromise the immune system such that the cat becomes susceptible to picking up secondary, opportunistic infections. Bacteria, viruses, protozoa and fungi that are present in a cat's normal environment and which pose no threat to a healthy cat, can now cause severe illness. It is these secondary infections that are responsible for most of the clinical signs associated with FIV and which are the main cause of death in FIV infected cats.

FIV infected cats can show many different symptoms due to the many different secondary infections that can be contracted. Recurrent illnesses (of any sort) can be indicative of a weakened immune system and so may suggest FIV or another different virus such as FeLV (Feline Leaukaemia Virus). FIV infected cats are more susceptible to a variety of infections of the skin, respiratory and urinary tracts, eyes, ears and mouth. These infections may be chronic or recurring and can be difficult to treat. Fever is common in later stages of the disease. Other symptoms can include: loss of appetite; lethargy; long-lasting or recurrent diarrhoea; seizures and other neurological disorders; anaemia.

How is FIV diagnosed?

FIV can be diagnosed by a simple blood test which looks for antibodies to the disease in the bloodstream. Unfortunately, the commonly used tests are not completely accurate and, for this reason, cats that test positive should be confirmed using a different test from a commercial laboratory.

A minority of infected cats do not produce antibodies at all. Blood tests to find the virus itself can be done but because the amount of virus in the bloodstream is small, special tests are needed. False positives and negatives can still occur.

It can take up to 12 weeks after initial infection before the blood test can detect that a cat has the virus. Hence, if you are worried that your cat has recently become infected (for example, following a cat fight), you should wait 12 weeks before testing.

The blood test can't be used for kittens under 20 weeks old born to an FIV-infected mother. Some of the kittens may not be infected with the virus but will still have antibodies against FIV from their mother - which will then produce a false positive result. If it is not known whether the mother is infected, it is best to wait until a kitten is older than 20 weeks old before testing.

Is it possible to vaccinate against FIV?

Currently, there is no vaccine available in the UK. There is a vaccine used in the United States but it is unreliable and doesn't provide protection against all the types of FIV (there are many different strains). A cat that has had this vaccination will subsequently test positive to FIV, which makes things tricky!

The best way to prevent FIV from spreading is to have your cat neutered or spayed. Importantly, this means keeping a kitten indoors until it has had the operation (at around 6 months old).

So how do you treat FIV?

Although there is no cure for FIV, provided the cat is healthy there will be no need for treatment. The main aim in managing the disease is to do everything possible to minimise the risks of secondary infections - by keeping the cat's immune system in as tip-top a condition as is possible.

FIV doesn't necessarily reduce a cat's lifespan and, in fact, many infected cats can live long, healthy and happy lives. To give them the best possible chance, you should do as much as you can to keep them in tip-top condition. FIV infected cats should:

• Live indoors. This will reduce the number of infections that they are exposed to, as well as eliminating the risk of infecting other neighbourhood cats
• Have as stress-free a life as possible
• Be neutered. This will eliminate the stress caused by coming on heat and reduces the desire to roam and act aggressively towards other cats
• Be kept up-to-date with their vaccinations
• Be kept up-to-date with flea and worming treatments
• Be fed a high-quality diet. They should not be fed raw foods that might carry bacteria such as raw eggs or milk
• Be taken for regular check-ups at the vets
• Have their weight monitored, since weight loss can be a sign of deterioration

You need to keep a look-out for the first sign of any illness, so that it can be treated immediately. Some FIV infected cats will benefit from the use of anti-viral products (which are used to treat human patients) however, these treatments are very expensive and the cat will need regular blood-testing for side effects, which may be worse in cats than they are in human patients. Interferons (which enhance or modify the immune system) can be used and may be effective in relieving symptoms.

You should discuss treatment of FIV and change of lifestyle for your FIV infected cat with your vet. They will have access to the most up-to-date information and will be in the best position to advise you.