FIV: Understanding Cat AIDS

FIV stands for feline immunodeficiency virus,but is more commonly understood as cat aids or feline HIV. It is a virus thatcauses immunosuppression, or a weakened immune system, in positive cats. Cat AIDS patients eventually become much more susceptible to infections because ofthis suppressed immune system, even getting very ill from organisms that arenaturally in the environment and that do not cause disease in negative cats,just as their human counterparts. However, while the virus behaves similarly toimmunodeficiency virus in humans, they are not the same disease and cannot betransmitted from cat to human or vice versa.

There are many misconceptions about cat-to-cattransmission, contagiousness, and even the time it takes for a cat to fall illfrom FIV, too. Just as an example, I lost a cat at 14 years old to the diseasewhen she had spent the last 14 years indoors and had never spent a day ill inher life. She also lived with 13 other cats during that time, including 3 ofher own kittens (whom she nursed), and none of them ever tested positive forfeline HIV.

What is FIV or cat AIDS?

Feline immunodeficiency virus is a retrovirus similar tofeline leukemia, but the two differ in behavior and means of transmission. Thevirus invades the white blood cells, specifically lymphocytes, and severelydamages or kills them over time. However, cats often remain symptom free for anaverage of 2-5 years after they become infected. In some cats, such as my own,it can be even longer.

Feline immunodeficiency virus goes through 3 stages: thefirst acute stage for 3-6 months following infection where the cat may havemild symptoms, the second subclinical stage where the cat is symptom-free andseemingly healthy for months to years, and the chronic stage, the cat AIDSstage, where the cat is chronically ill for months or years. Most feline HIVpatients appear completely normal and healthy for many years, as I experiencedwith my own cat.

Infected cats can live normal or near-normal life spans,depending on what viruses, bacteria, and fungi their bodies may need to fightoff throughout their lives. Eventually, though, FIV becomes more like cat AIDS,where the immune system is so severely weakened that the cat has no protectionagainst other infections, and these infections take their lives.

Prevalence and Transmission

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It is estimated that 15-20% of the cat population in the United Statesis infected with feline immunodeficiency virus, including as much as 3% of the“healthy cat” population. While a cat of any age can be diagnosed with catAIDS, it is most commonly diagnosed in cats 5-10 years old.

Because the feline version of HIV is transmitted through thebloodstream, just as human HIV is, the primary means of cat-to-cat transmissionis through bite wounds. This also explains why indoor-outdoor or free-roamingmale cats are twice as likely to have feline immunodeficiency virus as outdoorfemales, since they tend to be more territorial and to roam more often. Inrarer cases, FIV is transmitted through mating or from a nursing mother to herkittens.

Symptoms of FIV and Cat AIDS

It comes as no surprise that cat AIDS patients are often sufferingfrom recurrent infections of any kind, particularly skin, urinary, and upperrespiratory or eye infections. They are also prone to severe gingivitis, oftenextending throughout the mouth and throat. Similarly, they may have otherinfection related symptoms, such as:

  • A fever that does not go away or recurs frequently
  • Weight Loss
  • Poor Appetite
  • Lethargy

Cat AIDS patients may also have diarrhea, neurologicalconditions such as seizures or changes in behavior, blood diseases, and a poorhair coat. In reproductive females, a cat with feline immunodeficiency virusmay be more likely to miscarry her kittens or even be unable to conceive.

Diagnosing Cat AIDS

Feline immunodeficiency virus may be diagnosed throughroutine testing when a new cat is acquired or when a cat is ill and laboratorytesting is being performed. There may be a suspicion of infection first or the catmay be absolutely healthy in appearance. Also, it is important to remember thatmany of the symptoms of FIV are shared by many other diseases. In myexperience, the most consistent sign of infection once the cat is ill with thevirus is the severe gingivitis/stomatitis.

Most often, a test is performed on the blood either in theveterinarian’s office or at an outside lab. The test is for the detection ofantibodies to the virus.

cat with fiv
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If the initial test is positive, it MUST be repeated and/or furtherconfirmatory testing completed. It must also be remembered that kittens canhave a false positive test result due to antibodies passed from an infected momto the kittens. However, they can have these antibodies, which will subsideover time, and not be truly infected with the virus. Repeat testing isessential. Positive kittens should be retested every 2 months until they are 6months old. Most will revert to a negative status.

Unfortunately, there is an incubation period with cat AIDSwhich can result in a negative test result in a cat even though the cat hasbeen infected with the virus. For this reason, a negative cat with an unknownbackground or one known to have been exposed to a bite wound from another catshould be retested 2 to 3 months after the initial test.

Feline Immunodeficiency Virus Treatment Options

Unfortunately, there is no cure for feline immunodeficiencyvirus and the treatment options for the viral infection are very limited. Somecats with FIV are treated with therapeutic drugs similar to those used to treatHIV in humans, such as AZT (azothiouridine). This needs to be done carefullyunder a vet’s supervision, and the success rate is usually about the same asthose who are given supportive care only. Recombinant feline interferon mayalternatively be tried to help provide some anti-viral effects and helpregulate the immune system, but is often found to be limited in itshelpfulness.


The reason these drugs aren’t found to be extremely helpfulis that unfortunately, most cats are not started on a treatment regimen duringthe initial acute stage of the disease. These drugs are often found to be veryeffective in cats with early stage FIV, but in those with advanced chronicdisease, the treatment options do little except perhaps reduce the severity ofsymptoms.

Because there is no cure and treatment options are solimited, the biggest goal of FIV treatment is to provide supportive care. Thebiggest concerns for a positive cat are infections and inflammatory conditionsthat result from their weakened immune systems. Appropriate antibiotics andanti-inflammatory medications will be needed to keep these problems undercontrol and prevent them from becoming life-threatening. Aggressive management,including longer courses of antibiotics and quicker trips to the vet whensomething seems “off”, are an FIV-positive cat’s best chance at a good life.


cats with aids
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In theory, prevention of feline immunodeficiency virus issimple. Keep your cat indoors, away from other cats who have not been tested orare positive.

However, I know that some of you reading this and many catowners throughout the world do not believe in keeping your cats indoors. Whilethat is a personal decision, there are dangers, and it’s important tounderstand these dangers to make an educated decision. If you are going toallow your cat to go outdoors, make sure you spay or neuter your cat to helpdecrease the likelihood that he will roam or fight. Furthermore, educateyourself about vaccination. Too often, when I discuss the outdoor dangers forcats with a client, they say to me “But he has all his vaccines”. Pleaseunderstand that NO vaccine is perfect. NO vaccine protects everyone completely.

The FIV vaccine, unfortunately, is only found to beeffective protection in approximately 55-60% of vaccinated cats and also has seriousrisks associated with it. The biggest problem is that cats who are vaccinatedare going to test positive for feline immunodeficiency virus after having been vaccinated. That makes itimpossible for us to know the difference between a truly positive cat (one whois infected with the virus) and one who has been vaccinated and just hasantibodies to the virus. This makes management of all cats more difficult.

If you do decide on vaccination against the felineimmunodeficiency virus, make sure your cat is tested first to determine that heis truly negative. Furthermore, microchipping your cat would be critical. Ifyour vaccinated cat were to get lost, be picked up by animal control, or bebrought to a shelter and tested positive for FIV because she has antibodiesfrom the vaccine, she is very likely going to be euthanized. Microchips helpensure that you will be reunited.


Can I become infected with FIV?

There is no evidence that a person can become infected with the feline strand of immunodeficiency virus.


Can my FIV-positive cat live with other cats?

The virus is primarily passed from cat to cat through bite wounds.Cats with FIV are often found to be positive after years of living with othercats. In my case, my own cat lived with 13 others, and no one else in my cathousehold caught it because they never bit each other. Cats that live togetherdon't generally bite each other hard enough to break the skin even when inrough play.

It is recommended that you test all other cats in yourhousehold for FIV, separate those who fight often, and avoid introducing newcats to the family if you have a positive cat.


Isn’t cat AIDS the same thing as Feline Leukemia?

I have discovered over the years that there is sometimes themisconception that these two viruses or diseases are one and the same. This isnot true. The feline leukemia virus and the feline immunodeficiency virus aretwo separate viruses causing two different diseases. Many of the symptoms ofthe two diseases are alike, but neither the viruses nor the diseases are thesame.


When is it time to euthanize a cat with felineimmunodeficiency virus?

Many shelters and animal control facilities will euthanize acat with AIDS upon receiving that positive test result. Deciding when toeuthanize your own cat, however, who has lived for months or years with thedisease, is a very personal decision. The question and answer found hereillustrates some of the problems a cat parent may face when trying to make thisdecision.

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