Feline Immunodeficiency Virus

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  • Feline immunodeficiency virus at a glance

    • About: Feline immunodeficiency virus (FIV) is a viral infection that affects the immune
      system of cats. It is similar to the virus responsible for HIV in humans.
    • Transmission: The most common mode of infection is via deep bite wounds from infected cats. Entire
      males, in particular, have an increased risk due to territorial fighting.
    • Symptoms: Swollen lymph nodes, weight loss, poor coat condition, pale gums, chronic and recurrent infections.
    • Diagnosis: A blood test to look for antibodies to FIV can confirm the diagnosis.
    • Treatment: Supportive care will include veterinary monitoring, parasite control, keeping your cat indoors and a high-quality diet.
    • Can I catch FIV from my cat? Cats can not pass FIV on to humans.

    What is FIV?

    Feline immunodeficiency virus (FIV) 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 HIV in humans. FIV infects both domesticated cats, lions, tigers, pumas and cheetahs.

    FIV attacks the cells of the immune system, which leads to FAIDS (feline acquired immune deficiency syndrome), which is where the immune system has been compromised.

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

    • 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

    First isolated in a colony of cats in California in 1986, the virus is now worldwide. FIV affects 1.5-3% of cats in the United States.


    Direct contact

    The virus is present in large quantities in the cat’s saliva and blood.

    • Deep bite wounds. Free-roaming entire male cats are at higher risk as they are more likely to become involved in territorial fighting.
    • Blood transfusion from an infected cat.
    • Transmission has occurred during sexual intercourse, but it is not thought to be a major mode of infection. However, FIV can be passed on to the female from the biting that goes along with mating.

    Mutual grooming does not spread FIV.

    Vertical transmission

    Occasionally an FIV positive mother can pass the infection on to her kittens. This may happen either in utero or via infected milk; this most often occurs if the mother is shedding a high viral load during pregnancy or lactation.

    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?

    It is good practice to test any new cat or kitten who enters the home for FIV. Even if the cat is going to be the only cat in the household, it is important to know the HIV status for the following reasons:

    • To keep the cat inside, to reduce exposure to pathogens.
    • The cat will need to have more frequent veterinary visits than an FIV negative cat.
    • You can be on high alert for any minor changes to the cat’s health.

    What does FIV do?

    FIV affects 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+ lymphocytes). It then spreads to other lymph nodes throughout the body. At this time there may be an acute illness which is characterised by fever, low white blood cell count (leukopenia), low red blood cell count (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

    The asymptomatic phase can last for many years. During this stage, the cat appears healthy and can lead a normal life.

    Stage 3 – Final stage

    As we know, 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.


    The incubation period can range from months to years after exposure.

    Early symptoms

    Later symptoms

    • Weight loss
    • Poor coat condition
    • Vomiting
    • Diarrhea
    • Pale gums and lethargy due to anemia
    • Conjunctivitis
    • Red and inflamed gums due to gingivitis
    • Stomatitis – Inflammation of the mucous 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 higher risk of developing cancer and can develop lumps and bumps or sores which don’t heal


    Diagnosis is based on history, clinical signs and an ELISA blood test (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:


    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. The kitten doesn’t have FIV, just that he’s received antibodies to FIV. Re-test FIV positive kittens at a later date.


    It can take several weeks for antibodies to FIV to appear in the blood; if the cat is tested before this, it will show a negative result.

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

    The American Association of Feline Practitioners recommends all cats who have tested positive to FIV on the ELIZA test should be confirmed with a Western blot test or Immuno-Fluorescent antibody test. Further information on these tests can be found on this page.

    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 can be able to request a PCR (polymerase chain reaction) test, to detect the presence of FIV DNA in the blood.

    The veterinarian may perform additional checks to evaluate your cat’s general health status. These can include biochemical profile, complete blood count, and urinalysis


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

    Keep the cat indoors. There are many ways an outdoor cat can catch a bacterial, viral, parasitic or fungal infection outdoors, which include contaminated soil or water, hunting and exposure to other cats.

    Seek immediate medical care if any of the following symptoms occur:

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

    Some articles on Cat-World advocate a wait and see approach for cats who display mild symptoms; this does not apply to cats with FIV. At the first sign 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.

    Stage 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.
    • Maintain a proper vaccination regimen to protect your cat from other infectious diseases.
    • Keep your cat stress-free as stress impacts 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 for anemic cats.
    • High-calorie supplements.
    • Fluids to treat dehydration, where necessary.
    • Antibiotics to prevent or treat bacterial infections.

    Antiviral therapy

    • Interferons are proteins produced by the white blood cells in response to viruses, bacteria, parasites and tumour cells. A genetically engineered form of interferons is commercially available which can help by inhibiting viral replication as well as modulating the cat’s immune response.
    • Zidovudine (azidothymidine, AZT) is a drug used to prevent viral replication within the cells. Regular monitoring with complete blood counts is necessary for cats on this drug.

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


    The virus does not last outside the body for very long. The following disinfectants are effective against FIV.

    • Bleach (sodium hypochlorite, calcium hypochlorite or sodium dichloroisocyanurate)
    • Virox, Accel – Accelerated hydrogen peroxide
    • Trifectant or Virkon-Potassium peroxymonosulfate

    Living with an FIV positive cat

    Feed a high-quality commercial diet, and while I advocate raw food for cats, this does not include those with FIV.

    Bi-annual veterinary visits to monitor the progress of the disease, evaluate the cat’s health and pick up any problems early.

    Regardless of their indoor status, routinely treat your cat for parasites including worms and fleas. A stress-free environment is particularly important for cats with FIV.

    Should I have my FIV positive cat euthanised?

    No, this isn’t necessary, FIV positive cats can live for many years, especially if they receive prompt medical attention and supportive care. In fact, over the last ten years, many infected cats 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 acquire FIV via their mother tend to have a shorter lifespan. This is no doubt due to their immature immune systems, which are less able to keep the virus in check during the acute/first stage.


    Keep your cat inside: As FIV is spread via bites, keep the cat inside, and away from roaming cats. An outdoor enclosure is a good compromise.

    Desexing all cats: Desex all pet cats to reduce the desire to roam and fight.

    FIV test: Test all breeding cats before mating.

    FIV vaccine: 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 an FIV positive cat. It is not possible to differentiate a vaccinated cat from an FIV positive cat (who both have antibodies to the virus). Therefore your cat must have a microchip as a permanent form of identification.

    The FIV vaccine is 82% effective. It is made with A and D subtypes although it does offer protection against the common B clade. One study found the vaccine was 71% effective against this subtype. Cats who receive the vaccine will test positive for FIV.


    Un-neutered, free-roaming males are at the greatest risk of FIV; however, any outdoor cat is at risk.

    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 an infected 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 the home catch FIV?

    Yes, however, infection is not easy to spread, the greatest risk is if you have cats who don’t get along.

    Feline immunodeficiency virus (FIV) in cats infographic


    [1] BioMed Central


    • Julia Wilson, 'Cat World' Founder

      Julia Wilson is the founder of Cat-World, and has researched and written over 1,000 articles about cats. She is a cat expert with over 20 years of experience writing about a wide range of cat topics, with a special interest in cat health, welfare and preventative care. Julia lives in Sydney with her family, four cats and two dogs. Full author bio