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FIV, also known as “feline AIDS”, is a worldwide viral infection caused by the feline immunodeficiency virus. It is only infectious to felines, so neither humans nor other animals except cats can become infected. It is very similar to human AIDS infection in many ways.


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Although other bodily fluids are also potentially infectious, so that transmission is also possible during mating, blood transfusions, or from the queen to her puppies, males are primarily infected during fights through bites. This also means that tomcats, especially unneutered animals, are much more likely to be infected than neutered male or female cats.

In the outside world, the FIV virus can only survive for a few seconds, so that transmission through sharing food/water and lying areas or mutual cleaning does not usually lead to infections.

Course of infection

After the bite of an infected animal, fever and lymph node swelling occur, if at all, which is usually attributed to the actual bite and not to a possible FIV infection.

The virus penetrates certain immune cells and is integrated into the cell’s own DNA in such a way that these cells then produce FIV viruses, which in turn infect new immune cells.

The initial infection is followed by an asymptomatic phase, usually lasting years, without any signs of illness.

At some point, most cats will show unspecific symptoms and be susceptible to infections for a few months or years, as the affected immune cells are no longer able to protect against normally harmless bacteria, viruses, fungi and parasites.

Finally, an AIDS-like phase follows, during which infected animals contract infectious diseases more frequently and more severely, develop tumors, or even neurological symptoms, or show altered behavior before they ultimately die because the immune system breaks down completely.

Once a cat has been infected, it is always a persistent (lifelong) infection. There is no cure and the cat sheds the virus for life, making it a potential vector for other cats as well.

In very young cats, the infection is more progressive than in older animals.


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Among other things, there are swelling of the lymph nodes, fever, loss of appetite, weight loss, chronic inflammation of the mucous membrane of the mouth, anemia, tumors, changes in the eyes, neurological symptoms and infectious diseases.

The affected animals look unkempt and sick.


FIV can be detected by a blood test, detecting either the virus itself (direct detection) or, more commonly, the antibodies the body produces against the virus (indirect detection).

At the earliest 14 days, but more likely 4-6 weeks after infection, so-called “antibodies” can be detected.

These can also be passed on from infected mothers to the kittens with the milk, but without passing the infection on themselves, and can be detected there up to a maximum of 6 months of age.

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So positive antibody detection can come from animals that are actually infected, or from healthy animals under 6 months old.

Rapid tests are usually used for detection in practices or clinics. These detect antibodies and are about 95% reliable in the negative case. A positive test should always be checked again using another test method or a second antibody test.

The virus itself, on the other hand, can only be detected in special laboratories, which can usually be done from the blood, but also from infected tissue. This detection is also successful a few days after infection at the earliest and is very time-consuming. The certainty of virus detection varies depending on the test method.

In most cases, direct virus detection is used to confirm a positive antibody test.


The therapy of the FIV infection usually focuses on the treatment of secondary infections and their possible avoidance. The infected cat should be kept indoors for its own protection against infection, but also to protect other cats from contamination.

Various antiviral chemotherapeutic agents can be used to treat the FIV virus itself, which are intended to stop the progression of the infection but do not bring about a cure. The most important thing is an environment and attitude that is as low in pathogens and stress as possible.

Whether immunostimulating drugs are beneficial has not yet been clearly established. Although the immune system is stimulated, which leads to better protection against infections, but since the FIV virus mainly affects immune cells, their activation and multiplication could also lead to a progression of the virus itself.

Whether an infected cat should be vaccinated against other diseases must be decided on an individual basis. On the one hand, the vaccination protects against certain diseases to which an FIV-infected cat can be more susceptible, but on the other hand it activates the immune system with the same consequences as immunostimulating drugs.

There is no vaccination against FIV itself in Europe.

Whether one should separate infected and non-infected cats in a multi-cat household must also be decided individually. There are many examples where uninfected cats have lived with FIV positive animals for years without becoming infected because the social fabric was stable and no bites occurred.


FIV infection increases the risk of developing tumors and concomitant diseases. In some animals, this can lead to a reduced life expectancy.

On average, however, FIV-infected cats do not have a shorter lifespan. With good husbandry and care, they can live to a ripe old age. Thus, a positive FIV test alone is never a reason for euthanasia!

When should you take your cat to the vet?

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It is important to know your cat’s FIV status as positive animals require much more aggressive and prolonged anti-infection control.

The use of corticosteroids, vaccinations or immunostimulants should also be avoided in FIV-positive animals.

For this reason, a test is recommended with every new purchase (in multi-cat households BEFORE contact with your own animals). Also make sure that such a test has been carried out in animal shelters and animal welfare associations, as these tests are often not carried out as standard for cost reasons.

Outdoor cats should be tested at regular intervals (preferably annually). An FIV test is also advisable for ailing cats with stubborn infections and poorly healing wounds.