Feline Immunodeficiency Virus (FIV)

By Malcolm Weir, DVM, MSc, MPH; Amy Panning, DVM; Ernest Ward, DVM

three cats in a rowWhat is feline immunodeficiency virus?

Feline immunodeficiency virus (FIV) is a virus specific to the cat family. It is similar to HIV (human immunodeficiency virus, the cause of AIDS in people) in that it attacks and weakens the immune system and there is no cure. FIV was first recognized in the mid-1980s and has been found in cats worldwide. Although widespread, it is not a common infection in cats. Only 1-5% of cats show evidence of exposure to the virus. There are different strains of FIV, and some seem more harmful than others.

My cat has tested positive for FIV. Does my cat have feline AIDS?

Being FIV-positive is not the same as having feline AIDS (acquired immunodeficiency syndrome of cats). The FIV screening test (see below) detects antibodies that have been formed in your cat's blood because of infection with the feline immunodeficiency virus. An FIV-positive diagnosis means that your cat has been infected by the virus, but it may be years, if ever, before your cat develops the clinical signs referred to as feline AIDS.

Is my family at risk?

Absolutely not! Although HIV belongs to the same family of viruses as FIV, the two viruses infect different species. HIV infects only humans and FIV infects only cats. The viruses are very specific for their species and there is no risk of cross-infection between the immunodeficiency viruses of cats and people.

Are other cats in my household at risk?

Other cats in your household may have already been infected and should be tested. Spread between cats through normal social contact such as grooming is unlikely, so your other cats may be FIV-negative when tested. However, a cat that has FIV does present a risk to other cats.

Cat biting another catHow do cats get FIV?

Infected cats shed the virus mainly in their saliva. Naturally occurring transmission of an infection occurs when an infected cat that is actively shedding virus into the saliva bites another cat, directly inoculating its saliva through the bite wound. A susceptible cat can also become infected when other bodily fluids, particularly infected blood, enter its body. Infected blood may enter the cat's body through a bite wound, or the cat may become infected by means of a blood transfusion. The virus may also be sexually transmitted.

It is not surprising that many FIV-positive cats are known fighters, particularly those with a history of cat bite abscesses. Any cat bitten by another with an unknown medical history should be tested for FIV approximately two months after the bite.

"A cat bitten by another with an unknown medical history should be tested for FIV approximately two months after the bite."

The FIV organism is not able to survive for very long outside of living cells. This is another reason why casual infection is uncommon. Kittens may become infected before, at, or soon after birth. In these cases, it is believed that the virus is transmitted across the uterus during pregnancy or through the mother cat's milk during nursing. Around a quarter to a third of kittens born to an infected mother are likely to be infected themselves.

How is FIV diagnosed?

FIV is diagnosed through blood tests that detect antibodies to the virus. The most common screening test is called an ELISA test (enzyme-linked immunosorbent assay). A positive test result means that the cat has produced antibodies to the virus, and it is likely that it has been and still is infected by the virus. False positive results may occur if a cat has been vaccinated against FIV, since the antibody test does not differentiate between antibodies produced by the disease and vaccine-induced antibodies. Kittens born to an infected mother may receive maternal antibodies, or antibodies to the virus that pass through the milk, causing a false positive test result. Kittens under four months of age that test positive should be re-tested when they are six months old, by which time any maternal antibodies will have disappeared.

It can take up to eight weeks for a cat to develop antibodies to FIV, so a cat that has been recently infected with this virus may falsely test negative.

If a cat is diagnosed positive on the ELISA test, the results should be confirmed by retesting in eight weeks (for young kittens) or by submitting blood samples for a more definitive Western blot test or PCR (polymerase chain reaction) test.

Will my cat recover from FIV?

As far as we know, once a cat is infected with the FIV virus, it will remain infected for the rest of its life. However, it is not clear if all infected cats will become clinically ill. It may be weeks, months, or even years after initial infection with FIV before a cat will develop clinical signs of illness.

What type of disease does FIV cause?

FIV causes disease because it reduces the ability of the cat's immune system to respond to other infections. Infections that the cat would normally be able to recover from become prolonged or chronic. This means that many of the clinical signs associated with FIV are due to other non-healing infections.

"Many of the clinical signs associated with FIV are due to other non-healing infections."

Collectively, the signs seen as consequences of FIV are sometimes called feline AIDS. Common clinical signs of FIV infection include:

• Gingivitis/stomatitis (inflammation of the gums and mouth)

• Weight loss

• Poor appetite

• Fever, especially fever of unknown origin

• Inflammation of the membrane around the eyes (chronic conjunctivitis)

• Swollen lymph nodes

• Vomiting and diarrhea

Most of these signs are non-specific and many diseases can have a similar clinical picture. Any cat with persistent or recurrent illness or clinical signs should be tested for FIV, regardless of lifestyle.

Is there any treatment for FIV?

Secondary bacterial infections associated with feline AIDS can be effectively treated with antibiotics. Unfortunately, this is usually only temporary, as new infections will continue to occur because of the suppressed immune system. Some cats have been treated with human anti-HIV drugs, such as AZT (zidovudine, Retrovir), with some success. Certain antioxidants and immune-stimulating drugs may also be helpful. Talk with your veterinarian regarding these treatment options.

Should I have my cat euthanized?

Generally, this is not necessary until the late stages of disease. Like people with HIV, cats with FIV have a long period where they can appear healthy and show no clinical signs. This period may last for two to five years or perhaps even longer, during which your cat will have a normal, happy life.

How can I help my FIV-positive cat?

You can help your cat by ensuring it has a healthy lifestyle and is fed a high-quality diet, combined with twice-yearly examinations (including blood and urine tests) to monitor immune status. Any infections should be treated promptly and aggressively. Avoid feeding any FIV-positive cat a raw diet, as the pathogens that may be found in these foods may make your immune-compromised cat ill. Likewise, parasite control may be recommended for your cat in order to make sure they stay as healthy as possible.

"You can help your cat by ensuring it has a healthy lifestyle and is fed a high-quality diet."

Talk to your veterinarian about appropriate vaccines to give to your cat. Depending on their risk factors for contacting infected cats, or legal requirements in the area you live in, your vet may or may not recommend vaccines for your FIV-positive cat. The better the general health of your cat, the longer the asymptomatic (no obvious disease) period tends to be. Keeping an FIV-infected cat indoors is mandatory for the health of the neighborhood cats, as well as reducing the likelihood that your cat will pick up infections from other cats.

How can I prevent my cat from becoming infected and is there a vaccine?

As most cats become infected from bite wounds during fighting, the risk of FIV infection can be minimized by making sure your cat is neutered and, where possible, kept indoors. There is no vaccine currently available.

One cat in my household is FIV-positive and the others are not. What should I do?

There are two options:

1. Ideally, place the FIV-positive cat in a home with no other cats.

2. As the risk of infection spreading to your other cats by social contact is low, you may choose to keep the FIV-positive cat with your other cats. In this case, the positive cat should have a separate feeding bowl from the other cats and food should not be left out for all cats to share.

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