Feline Leukaemia Virus (FeLV)

isolated cat


  • Feline Leukaemia Virus (FeLV) is a serious disease that attacks the immune system and causes cancers such as lymphoma and leukaemia.
  • Because FeLV damages the immune system, it increases the risk of other infections and diseases.
  • FeLV spreads in bodily fluids such as saliva, snot, urine and faeces.
  • Young, unvaccinated, un-neutered, outdoor cats living around lots of other cats are most at risk of catching FeLV.
  • Sadly, most cats die within a few years of catching FeLV.
  • Protect your cat with regular FeLV vaccinations.

What is Feline Leukaemia Virus?

Feline Leukaemia Virus (FeLV) is a virus that attacks the immune system and causes cancers such as lymphoma and leukaemia. Cats with FeLV have an increased risk of developing other infections and diseases.

FeLV is most common among young, unvaccinated, un-neutered, outdoor cats.

FeLV spreads in the bodily fluids of infected cats, i.e. their saliva (dribble), snot, urine and poo. It can be spread via sneezing, licking and biting, and by sharing food bowls or litter trays with an infected cat. Kittens can catch FeLV inside the womb, and from their mother’s milk.

A small proportion of cats manage to fight FeLV and recover (usually vaccinated cats) but sadly, most cats can’t fight it, and become very poorly. In some rare cases, cats with FeLV carry the virus but appear healthy; these cats are at risk of becoming poorly at any time and can spread FeLV to others.


The first symptoms of FeLV often go unnoticed because they tend to be mild and vague i.e. low energy/being out of sorts. Severe symptoms start to appear when FeLV becomes more advanced, i.e. a cancer or infection develops.

Symptoms often include:

Please note many of the symptoms listed above are common and can indicate many conditions other than FeLV.

When to contact your vet

Visit your vet if you are concerned about FeLV. If your cat has been previously diagnosed with FeLV and seems ‘out-of-sorts’ have them, checked ASAP.

You know your cat best. If they don’t have the symptoms listed above, but you are still concerned it’s always best to contact your vet.


Your vet can diagnose FeLV with blood tests.


There is no cure for FeLV. If your cat has it, you will need to work closely with your vet to keep them well for as long as possible. FeLV weakens the immune system, making other infection and disease more likely. Your cat will need regular vet checks and special care at home. Sadly, many cats with FeLV become so poorly that they need to be put to sleep to prevent suffering. If your cat has FeLV and seems unwell, take them to the vet straight away to prevent life-threatening problems developing.

Home care

Cats with FeLV must be kept indoors. This is to protect them from other infections and prevent the spread of FeLV to other cats.

Live as a single cat. Cats with FeLV shouldn’t live with other cats. If you own more than one cat, and one of them has FeLV, you should keep them separate. Fortunately, many cats prefer living without other cats, so this is isn’t often a problem.

Neutering. All cats with FeLV should be neutered (castrated or speyed) to reduce roaming, fighting and the spread of FeLV.

Regular vet checks. Have your cat vet-checked every 6-12 months (more often if necessary).

Flea and Worm. It’s important to regularly treat for fleas and worms if your cat has FeLV.

Always feed cooked food. Cats with FeLV have a weak immune system and may not be able to fight off any germs in raw food.


Sadly, most cats with Feline Leukaemia Virus die or need to be put-to-sleep within three years of diagnosis.


Vaccination and testing. The best way to prevent FeLV is to vaccinate annually. Before introducing a new cat to your home, it’s a good idea to have them vet checked and vaccinated for FeLV. In some scenarios, your vet may recommend testing for FeLV before vaccinating.


Can people or dogs get FeLV?

No, only cats suffer from FeLV.

Are FIV and FeLV the same thing?

No, FeLV is ‘Feline Leukaemia Virus’ and FIV is ‘Feline Immunodeficiency Virus’. They are different diseases caused by different viruses. Both diseases cause similar symptoms and weaken the immune system. There is a separate blood test for FIV.


Treatment for a poorly cat with FeLV can become very expensive. Consider insuring your cat as soon as you get them, before any signs of illness start. This will ensure you have all the support you need to care for them.

It’s also very important to speak openly to your vet about your finances, the cost of treatment, as well as what you think is right for your cat. There are often several treatment options so if one doesn’t work for you and your pet then your vet may be able to offer another.

Published: July 2019

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Written by vets and vet nurses. This advice is for UK pets only.

Illustrations by Samantha Elmhurst