Feline Immunodeficiency Virus (Cat Aids)

What is FIV?   What are the symptoms of FIV in cats?   How is FIV transmitted?   Diagnosing FIV   Should I have my FIV positive cat euthanised?   Preventing FIV in cats   Which cats are most at risk of catching FIV   Can I catch FIV from my cat?

FIV in catsWhat is FIV?

Also known as FIV or cat AIDS, feline immunodeficiency virus is an infectious disease caused by an  RNA lentivirus (slow-acting viruses) of the retrovirus family. It is in the same family as the feline leukemia virus (FeLV) and is similar to the HIV virus in humans. FIV infects both domesticated cats, lions, tigers, pumas and cheetahs.

FIV attacks the cells of the immune system, leading to FAIDS (feline acquired immune deficiency syndrome). This compromises the cat’s ability to fight off infections.

There are five known subtypes of FIV (known as clades) [1]. Each clade contains substrains.

These are:

  • A – USA (most common on the west coast), Australia (predominant) and the United Kingdom
  • B – USA (most common on the east coast), Australia (rare) and Europe
  • C – California, Canada and Taiwan
  • D – Japan
  • E – Argentina

It was first discovered in 1986 in a colony of cats in California and is found worldwide. Between 2 – 4% of cats are infected with FIV globally.

AnchorHow is FIV transmitted?

The virus is present in large quantities in the cat’s saliva, and the most common mode of transmission is via deep bite wounds which occur during fighting. Free roaming, entire male cats are at greater risk as they are more likely to become involved in territorial fighting.

Occasionally FIV is passed onto kittens whose mother is FIV positive. This may happen either in utero or via infected milk, this most often happens if the mother is shedding a high viral load during pregnancy or lactation.

Cats don’t become infected via mutual grooming, and while the virus has been transmitted experimentally during sexual intercourse, it is not believed to be a major mode of transmission, although FIV can be passed on to the female from the biting that goes along with mating.

Unlike other pathogens, the FIV does not last long in the environment and fomites (objects such as food bowls, blankets or toys which carry infection) are not a risk.

Should all cats be tested for FIV?

Yes, it is a good idea to have any new cat or kitten who enters the household to be tested for FIV. Even if he is going to be the only cat in the household, it is important to know his HIV status for the following reasons.

  • So that he can be kept indoors, which reduces his exposure to pathogens.
  • He will need to have more frequent veterinary visits than an FIV negative cat.
  • You can be on high alert for any minor changes to his health so that you can keep him healthy.

What does FIV do?

FIV attacks the cat’s immune system which makes it vulnerable to secondary bacterial, viral, fungal and protozoal infections.

Stage 1 – Acute stage: Once inside the body, FIV is carried to the regional lymph nodes where it replicates in the white blood cells known as T lymphocytes (CD4+ lymphocyte). It then spreads to other lymph nodes throughout the body. At this time there may be an acute illness which is characterised by fever, leukopenia, anemia, malaise and swollen lymph nodes, lasting a few weeks. During this initial stage, it may go unnoticed that the cat is unwell.

Stage 2 – Latent stage: This is the asymptomatic phase which can last for many years. During this stage, the cat appears healthy and is able to lead a normal life.

Stage 3 – Final stage: As we’ve already discussed, FIV destroys the T lymphocytes, these cells are required for the proper functioning of the immune system. Every day cats are exposed to a host of infectious pathogens (disease-causing organisms), however, the immune system protects the cat from developing an infection.  Eventually, when enough T lymphocytes have been destroyed, the immune system loses its ability to fight off opportunistic infections.

What are the symptoms of FIV?

Cats show a range of symptoms in this stage, these symptoms may vary from cat to cat.

Early symptoms:

  • Fever
  • Swollen lymph nodes
  • Lethargy

Later symptoms:

  • Weight loss
  • Poor coat condition
  • Vomiting
  • Diarrhea
  • Pale gums and lethargy due to anemia
  • Conjunctivitis – Inflammation of the conjunctiva in the eye
  • Bad breath
  • Gingivitis – Red and inflamed gums
  • Stomatitis – Inflammation of the mucus membranes which may progress to mouth ulcers
  • Chronic or recurrent infections of the skin, eyes, urinary tract, respiratory tract etc.
  • Cats with FIV are at greater risk of developing cancer, look out for lumps and bumps or sores which don’t heal

How is FIV diagnosed?

FIV is diagnosed based on history, clinical signs and a blood test known as ELISA (enzyme-linked immunosorbent assay), which detects antibodies to FIV. It is possible to get false positive or false negatives from these results for the following reasons:

False positive:

If a cat has received the FIV vaccine it will have a positive test result.

Kittens born to FIV-infected mothers or mothers who have had the FIV vaccination may have received antibodies from their mother’s milk. This doesn’t mean that the kitten has FIV, just that he’s received antibodies to FIV. Kittens who test positive should be re-tested at a later date.

False negative:

It usually takes several weeks for antibodies to FIV to appear in the blood, if the cat is tested prior to this it will show a negative result.

If the cat is in the later stages of infection it may not be producing antibodies.

FIV PCR (polymerase chain reaction) test: This test is available in some commercial laboratories. PCR detects the presence of the FIV virus in the blood.

Western blot test or IFA (Immuno-Fluorescent Antibody Test): If a cat has tested positive for FIV it is sometimes recommended to follow up with either a Western Blot Test or an IFA test.

If your cat has tested positive for FIV but you are not sure if it has had the vaccine or want to be sure it does/doesn’t have the virus then you may be able to request a PCR (polymerase chain reaction) test, which will be able to detect the presence of FIV DNA in the blood.

Additional tests may be performed to check your cat’s overall health. These can include complete blood count, biochemical profile and urinalysis.

How is FIV treated?

There is no cure for FIV, once a cat has it, it is for life. The goal is to provide supportive care to the infected cat.

The first step is to keep your cat indoors. There are many ways an outdoor cat can catch a bacterial, viral, parasitic or fungal infection outdoors including contaminated soil or water, hunting and exposure to other cats.

Ensuring that prompt veterinary attention is sought at the first sign of illness including:

  • Loss of appetite
  • Lethargy
  • Fever
  • Dehydration
  • Eye or nasal discharge
  • Lumps or bumps
  • Sores which don’t heal
  • Vomiting
  • Diarrhea
  • Cough

Some articles on this site advocate a wait and see approach in cats displaying mild symptoms, however, this does not apply to cats with FIV. At the first sight of illness, see your veterinarian as cats who are FIV positive don’t have the resources to recover from mild and self-limiting illness as a cat with a healthy immune system has. It is always better to err on the side of safety and have your cat checked.

Stages one and two:

  • Regular veterinary check ups. FIV-positive cats should see a veterinarian at least twice a year for check-ups.
  • Maintaining proper flea and worm control.
  • Feed a high-quality commercial diet is the best option for an FIV cat. If you do feed your cat a homemade diet, make sure the meat is cooked. Human grade raw meat is generally safe for healthy cats to eat, but cats with FIV are at greater risk due to their immunocompromised state.
  • Maintain a proper vaccination regimen to protect your cat from other infectious diseases.
  • Your cat should be kept as stress-free as possible as stress is known to have an impact on the immune system. Avoid changes in the household, if you do have other pets, make sure resources such as litter trays, food and toys are plentiful.

Stage three:

  • Blood transfusions if your cat has become anemia.
  • High-calorie supplements.
  • There are other drugs available such as interferon and AZT which have been used in some cats, but it is best to speak to your veterinarian about these.
  • Fluids to treat dehydration, where necessary.
  • Your cat may be prescribed antibiotics to prevent or treat bacterial infections.

If your FIV positive cat is in a multi-cat household (FIV positive or negative), he should be isolated if there is an outbreak of disease among cats. Even minor sniffles which an immunocompetent cat may shrug off can become life threatening to a cat with FIV.

Should cats with FIV be euthanised?

No, this isn’t necessary. FIV positive cats can live for many years, especially if they are given prompt medical attention when necessary and supportive care. In fact, over the last ten years, many infected cats die live long enough to die of age-related disease and don’t ever show signs of illness related to FIV.

What is the life expectancy of a cat with FIV?

The median survival time of a cat infected with FIV is five years, although many can live for longer than that. Considering the average lifespan of a cat is 12-15 years, five years is quite a long time in cat terms. Kittens who become infected via their mother tend to have a shorter lifespan, no doubt due to their immature immune systems which are less able to keep the virus in check during the acute/first stage.

The only reason a FIV positive cat should be euthanised is if he is suffering from an illness which can not be cured and is affecting his quality of life.

Preventing FIV in cats

Desexing of all pets, not allowing them to roam free and testing all cats used for breeding.

There is now an FIV vaccine which is available, it is said to be 82% effective. The vaccine is made with A and D subtypes although does offer protection against the common B clade with one study finding the vaccine 71% effective against this subtype.

Cats given the vaccine will test positive for FIV which may result in confusion, especially in the case of a cat being picked up by a shelter or council.

Another reason for caution is the vaccine contains an adjuvant, which is a chemical added to the vaccine to stimulate an immune response. However, this has the potential to cause an injection site sarcoma.

The American Association of Feline Practitioners recommends the vaccine be given to cats who are at high-risk, such as those allowed to roam outside and cats who live in a household with a FIV positive cat. Due to the fact that it is not possible to differentiate a vaccinated cat from an FIV positive cat (who will both have antibodies to the virus), it is important to make sure your cat is properly identified with a microchip and your details are kept up to date on the database.

Which cats are at greatest risk of catching FIV?

Un-neutered, free-roaming males are at the greatest risk of FIV, although any cat allowed to free roam is at risk of catching FIV.

Can FIV positive and FIV negative cats live in the same household?

The general opinion is yes, this is okay as long as there isn’t any fighting between the cats. As FIV positive cats are more susceptible to opportunistic infections it is important to ensure the health and vaccination status of ALL cats in the household.

Others suggest either keeping FIV positive cats isolated from FIV negative cats or rehoming the FIV positive cat in a single cat household. Your veterinarian is the best person to speak to in this regard.

Can I catch FIV from my cat?

No, it is not possible to catch FIV from your cat, nor is it possible for your cat to catch HIV from a human. While both viruses come from the same family, they are species specific. Dogs can also not catch FIV from cats.

Can other cats in my home catch FIV?

Yes, this is possible although infection is not easily spread. The greatest risk is if you have cats who don’t get along. In this situation, it is recommended that cats who don’t get along (where one is positive) should be kept apart or rehomed where possible. Usually, the FIV negative cat would be rehomed as FIV positive cats can be harder to adopt.

For more information on FIV in cats, this is a comprehensive site.


[1] BioMed Central

Related articles:

Feline Leukemia   Cat symptoms

Last updated 22nd February 2017.

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