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Feline immunodeficiency virus at a
Feline immunodeficiency virus (FIV or cat AIDS) 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 (clades) . 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 2-4% of cats globally.
The virus is present in large quantities in the cat’s saliva, and FIV is spread primarily via deep bite wounds. Free roaming, entire male cats are at greater risk as they are more likely to become involved in territorial fighting.
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.
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 happens 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.
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.
- To keep him inside, reducing 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.
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, 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 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 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.
- Swollen lymph nodes
- Weight loss
- Poor coat condition
- 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
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 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.
The American Association of Feline Practitioners recommend all cats who have tested positive to FIV on the ELIZA test should be confirmed with 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.
Your veterinarian may perform additional checks to evaluate your cat’s general health status. These can include complete blood count, biochemical profile 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 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.
Seek immediate medical care if any of the following symptoms occur:
- Loss of appetite
- Eye or nasal discharge
- Lumps or bumps
- Sores which don’t heal
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.
- 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.
- Blood transfusions if your cat has become anemia.
- High-calorie supplements.
- Fluids to treat dehydration, where necessary.
- Antibiotics to prevent or treat bacterial infections.
- 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 own immune response.
- Zidovudine (azidothymidine, AZT) is a drug used to prevent viral replication within the cells. Regular monitoring with complete blood counts are 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:
FIV cats should be fed a high-quality commercial diet, and while I advocate raw food for cats, this does not include those with FIV.
Bi-annual veterinary visits are important to evaluate your 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.
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 die live long enough to die of age-related disease and don’t ever show signs of illness related to 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.
Keep your cat inside:
As FIV is spread via bites, keeping your cat inside, and away from roaming cats. An outdoor enclosure is a good compromise.
Desex all pet cats to reduce the desire to roam and fight.
Test all breeding cats prior to mating.
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 it is important that your cat has a microchip as a permanent form of identification.
The FIV vaccine is 82% effective. It 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 who receive the vaccine will test positive for 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.
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.
Yes, however, infection is not easy to spread, the greatest risk is if you have cats who don’t get along.