FIV and FeLV in Cats
What are FeLV and FIV?

Feline leukaemia virus (FeLV) and feline immunodeficiency virus (FIV) both belong to the same group of viruses, the retrovirus group. This means they are somewhat related to one another and act in a similar way.

Retroviruses such as FeLV and FIV are particularly successful because the immune system usually fails to remove them completely (unlike many other viruses), so affected cats become infected for life. Feline immunodeficiency virus (FIV) is related to the human immunodeficiency virus (HIV), however humans and cats cannot infect each other with their respective viruses.

How do cats catch FeLV or FIV?
Cats can get FeLV and FIV through contact with other cats.

Feline leukaemia virus is usually transmitted through saliva, most commonly by friendly, social cats who like mutual grooming and do not mind sharing food bowls. However, FeLV can also be transmitted through bites.

Feline immunodeficiency virus is usually transmitted through biting by an infected cat, so individuals with FIV are typically entire tom cats or any other cats that like fighting.
What are the clinical signs of FeLV or FIV?
Both FeLV and FIV cause similar problems by gradually weakening the immune system. Infected cats become prone to infections that a healthy immune system would often just fight off. Infected cats in advanced stages of the disease have a much higher chance of developing a cancerous disease. Anaemia is another common problem, particularly in cats with FeLV. Despite its name, feline leukaemia virus does not necessarily cause leukaemia – it can do so, but it also causes a multitude of other diseases.

There are no typical clinical signs for either disease. Vets usually become suspicious when cats are presented either with persisting infections which they should be able to fight off, or with ‘non-standard’ disease, or with several concurrent infectious problems.
How is the disease diagnosed?

There are two possible situations in which tests are carried out for either FeLV or FIV.

  • FeLV or FIV is suspected as an underlying disease
  • A healthy cat is tested for FeLV and FIV to ensure that he or she is not carrying the virus already.

Whatever the reason for testing a cat, it is usually possible to diagnose FeLV and FIV with a blood test that can be done at the practice. However, in some cases we may suggest sending a blood sample to a laboratory for more advanced testing methods to be used.

Can FeLV or FIV be treated?
Cats carrying FeLV and FIV virus cannot be cured. HIV. In human medicine, advanced anti-viral drugs are now available – these can effectively suppress the activity of the virus for long periods of time. Few of these (very costly) drugs have been used in cats and it is not known whether such drugs are effective for FeLV/FIV or safe for cats to take.

As the majority of clinical signs caused by both FeLV and FIV are due to a non-functioning immune system, it is often possible to treat any secondary infections or problems, thereby giving the patient a reasonable quality of life for a longer period of time.

It must be remembered that the infected individual is a danger to the rest of the cat population and will spread FeLV or FIV unless he or she is kept isolated from other cats.
How can FeLV or FIV be treated?
Whilst FeLV cannot be treated once a cat carries the disease, it is possible to prevent infection by vaccination. FeLV vaccination is advisable for all cats that can go out or have contact with cats that go outdoors.

Unfortunately, there is no FIV vaccine which is licensed for use in the UK, so prevention is much more difficult than it is for FeLV. Any cat that is not kept indoors at all times is at risk of infection with FIV.
What happens if your cat tests positive?
This can depend very much on why your cat has been tested. If he or she was tested because of severe or recurrent illness and is positive for one or both diseases, this means that the disease is already present, and the immune system is already compromised. Under these circumstances unfortunately the outlook may be poor. It may be possible to give your cat a reasonable quality of life for a period of time with medication and very good care. However, he or she will be shedding the virus and will therefore be a danger to other cats.

If your FeLV or FIV positive cat is otherwise healthy and was tested as a routine precaution, then the outlook depends very much on the particular, individual animal, it may take months or even many years before the disease breaks out and the cat will seem healthy in the meantime. However, he or she will be able to pass on the virus to other cats. This means that your cat should be kept indoors and away from other cats.