Feline Immunodeficiency Virus (FIV) is an important disease agent of cats.  It is sometimes referred to as the Feline AIDS Virus because just like human HIV, the FIV virus attacks the immune system.  The two diseases are very similar between the two species.  Fortunately, most viruses are species specific, thus FIV cannot be transmitted to any other animal, including humans; HIV cannot be transmitted to animals.

How is FIV transmitted?

FIV is transmitted several ways. The first way it can be transmitted is through the placenta or milk, thus newborn kittens can become infected from the queen (mother cat).  Secondly, adult cats can FIV through bite wounds that occur in cat fights.  A FIV negative cat could acquire FIV by either biting an infected cat or the infected cat biting the negative cat.  Sharing food and water bowls or cats the groom each other has not been shown to be a significant transmission route.

Is my cat at risk for getting FIV?

If your cat is strictly outdoors or is an indoor/outdoor cat, your cat is at risk for getting FIV.  Any cat that roams and/or gets into fights with other cats could acquire the virus.  However, your cat will not get FIV by just walking across an area that a FIV cat just walked across.  If your cat is supervised outside, meaning you watch your cat for the time your cat is outside, then your cat is at a low risk for getting FIV.  If you cat is strictly indoors, then your cat cannot get FIV from an infected cat.

How do I know my cat has FIV?

The only way to know that your cat has FIV is to do a blood test.  If the test is positive, then other blood tests are required to confirm it.  The test of choice to confirm an earlier positive is called a Western Blot test.  The screening test could have a false positive, thus the need for a follow up test.  The reason a Western Blot is not done for every test is because it is expensive and cost prohibitive to run every time.  The screening test is fairly inexpensive and easy to run.  The screening blood test is fairly accurate and there are rarely, if any, false negatives.  If you cat tests positive, ask your veterinarian to run a Western Blot FIV test to confirm the test result.

Can I protect my cat from getting FIV?

Unfortunately there is no vaccine to give cats in order that they not acquire FIV.  Many researchers are trying to develop a vaccine but there just isn't a good way to prevent your cat from getting FIV other than keeping your cat indoors all the time.  If your cat goes outdoors, it is recommended that your cat be tested every year for FIV at his or her annual exam.  If your veterinarian does not routinely offer FIV at every annual check up, please ask your veterinarian to check your cat for FIV.  This annual check doesn't help your cat from getting FIV, but it does tell you if your cat has it and to now keep your cat indoor 100% so that your cat doesn't contribute to the spread of the disease.  The only way to prevent disease is to keep your cat inside.

What are the clinical signs of FIV?

Many cats will be asymptomatic (free of) signs for months to years before overt illness will show.  This incubation period, where there are no signs, can be as long as six years, thus the need to test your cat annually.

When clinical signs do show, there is a wide range of signs.  This is because the virus can affect any system in body.  FIV cats can show severe gingival infection or redness, fever, lethargy, inappetance, respiratory infections, delayed wound healing, prolonged recovery from infections, weight loss and unkempt hair coat.  However, these are just some of the more common signs.  The virus can affect the nervous system, the eyes, the muscles, and gastrointestinal system and more.  The cat should be tested for FIV if the cat has access to the outdoors and the clinical signs suggest FIV.  Your veterinarian will discuss it with you.  Also, some cats with FIV are more prone to developing certain tumors like lymphoma.

Interpreting test results

Adult Cats:
• From the time of initial virus inoculation into the cats, it may take up to two years for the test to turn positive.  Therefore, a test could be negative for a year or two even if the virus is present in the cat.  Thus all cats with access to outdoors should be tested yearly.
• When some cats become terminally ill with FIV, the test may turn negative.  This happens because antibodies against the virus become attached and bound to the large amount of virus present.  Since the test detects antibodies, not virus particles, which are free in circulation, the test may be falsely negative.  This does not mean the cat does not have the virus anymore, it only means it is a false negative result.  As mentioned before, this is an extremely rare scenario.

Kittens:
• Most kittens under 4 months of age that test positive have not been exposed to the virus.  Instead, the test is detecting the antibodies that were passed from the mother to the kitten.  These antibodies may persist in the kitten until the kitten is 6 months old.  Therefore, if a kitten is positive, it should be retested after 6 months of age.  Again, kittens can become infected from their mother so a positive result cannot differentiate if the antibodies are from the mother or the actual kitten's immune system.  If the kitten tests negative after 6 months of age, then there is no worry.

Is Treatment Available?

Just as with HIV, there are no treatments to cure a cat with FIV.  Many cats will live years with no or minimal symptoms.  Just because a cat tests positive for FIV does not mean the cat has to be euthanized immediately.  If a cat is severely ill from FIV, then treatment to stabilize the cat is much harder.  Cats with FIV can get secondary bacterial diseases.  These diseases can be treated with antibiotics.  Some immune stimulant drugs (e.g. Interferon) are available to help boost the cat's immune system but it will not get rid of the virus.  Your cat could live many years with FIV or may only live a few months.  It is very case dependent and also depends on the signs seen in each case.

Prognosis

The long term prognosis is poor; meaning most cats won't live another 10 years.  Some cats will live a very “healthy” asymptomatic life for 2-5 years, or more, after diagnosis.