All About Feline Immunodeficiency Virus (FIV)

This disease weakens a cat's immune system and the symptoms aren't easy to spot. It's very common amongst stray cats, so it's important to try and prevent your cat from coming into contact with them.
All About Feline Immunodeficiency Virus (FIV)
Francisco María García

Written and verified by the lawyer Francisco María García.

Last update: 21 December, 2022

Experts also know Feline Immunodeficiency Virus (FIV) as feline AIDS and it’s a disease that weakens the immune system. A cat gets infected when the virus enters the bloodstream and this normally happens when they’re bitten by an infected cat.

It’s similar to feline leukemia, but leukemia is a retrovirus whilst FIV is a lentivirus, and, in medicine, there are big differences between the two.

Infection is common amongst male cats that go outside a lot, normally because they fight other male cats over females in heat. In fact, it’s almost impossible for house cats to get infected if they’ve been castrated. Females are also at risk of catching the virus, as well as their kittens when giving birth or breastfeeding.

Only between 1.5 and 3% of the cat population is infected, although the virus accounts for 15% of cat illnesses.

Because it’s a disease that attacks the immune system, it’s difficult to identify. It might be the case that the only symptom is that your cat is more susceptible to other illnesses.

A cat with green eyes staring straight ahead.

Symptoms of Feline Immunodeficiency Virus

As we’ve mentioned, the feline immunodeficiency virus makes a cat much more vulnerable to other illnesses that they wouldn’t suffer from if their immune system was healthy.

As a result, one symptom of this disease could be that your cat gets sick with an illness that they’ve already been treated for. Another symptom is if they frequently suffer from secondary infections, such as skin problems, gum problems, urinary infections, or respiratory infections. You might note that they’re losing a lot of fur, losing weight, or have a fever with no apparent justification.

What to do if your cat is infected

If you suspect that your cat has this infection, you should go straight to your vet for a proper diagnosis.

This illness causes a decrease in leukocytes and white blood cells, which are responsible for fighting infections. Anemia is also common.

This virus still has no vaccine. However, it’s also important to note that they can’t pass it on to humans.

A cat with blue eyes lying down.

There are two differing opinions among experts regarding how cats get infected. Some claim that it’s unusual and quite difficult to get infected, whilst others claim that cats can even catch it through saliva or other bodily fluids.

Avoiding infection

Although there’s currently no cure for this disease, it’s possible to keep the effects under control. So, the key is to try to keep your cat free from other illnesses, prevent them from infecting others, and otherwise try to maintain their quality of life. To do this, the following measures can be helpful:

  • Take extra care with their overall hygiene and their environment to protect them from opportunist illnesses. Make sure they’re up to date with their vaccinations and try to protect them from bacterial infections.
  • Make sure they’ve had their anti-parasite treatments. The treatment for this illness, although it’s incurable, involves antivirals and immunomodulators.
  • If your cat gets sick, make sure they’re treated and make a full recovery so as to avoid relapses.
  • Follow any treatment suggestions by your vet, such as transfusions, special diets, and intravenous hydration. They may also prescribe some anti-inflammatories and anabolic steroids.
  • Have your cat castrated to prevent them from fighting and infecting other cats.
  • If possible, try to prevent your cat from leaving the house. They’re likely to infect another cat if they bite them.
  • If they live with other cats, try to prevent them from fighting so as to avoid any open wounds.


As you can see, the Feline Immunodeficiency Virus doesn’t necessarily need to be a serious matter for your cat. They can still live a long life if you take care of them properly.

However, despite your best efforts, their health and well-being will still be significantly affected. If your cat is getting sick frequently, the kindest thing may well be to have them put to sleep peacefully.

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All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.

  • Viuche, W. C., Díaz, C. A. R., Cuellar, P. A. R., Julian, S. C., & Sánchez, D. C. (2017). Leucemia e inmunodeficiencia felina. Reporte de un caso. REDVET. Revista Electrónica de Veterinaria, 18(10), 1-9.
  • Ayala, I., Talone, T., Castillo, C., Gerardi, G., & Hernandez, J. (1998). El síndrome de inmunodeficiencia adquirida del gato causado por el FIV (Feline Immunodeficiency Virus). Archivos de medicina veterinaria, 30(1), 5-12.

The contents of My Animals are written for informational purposes. They can't replace the diagnosis, advice, or treatment from a professional. In the case of any doubt, it's best to consult a trusted specialist.