What’s feline leukemia?

Feline leukemia, also known as FeLV, is one of the most common infectious diseases in cats and, sadly, it is ultimately fatal in most cases.

The virus gradually gets worse over time and can develop into a number of different disorders, including:

  • anaemia
  • cancer (particularly lymphoma and leukemia)
  • suppression of the immune system (increasing the risk of other infections)
  • immune-mediated disease (when the cat’s immune system causes damage to its own cells)
  • loss of pregnancy
  • intestinal inflammation
  • neurologic problems (including nerve dysfunction and blindness)
  • severe mouth inflammation

Is FeLV always fatal?

Usually, but not always. Around 30% of cats exposed to the virus are able to mount an effective immune response. This means they are able to eliminate the virus and won’t develop persistent infections. However, until the infection is cleared, these cats carry the virus and damage can be done during this time that may lead to disease later in life.

Causes and symptoms

How is the feline leukemia virus transmitted?

FeLV can be passed to other cats through infected blood and saliva and, in rare cases, urine and faeces. Grooming and fighting are the most common ways for the virus to spread. An infected mother can also pass on the virus to her kittens before they are born or through her milk.

Leukemia in cats signs

FeLV is often spread by cats that appear to be healthy, so even if a cat doesn’t appear to be unwell, it could be infected and able to transmit the virus.

If there are initial symptoms, they are typically mild. As the disease develops over time (weeks, months, or even years) an infected cat’s health may progressively deteriorate or they may experience repeating cycles of illness. Signs of cat leukemia vary due to the number of disorders which can result, but may include:

  • Loss of appetite
  • Progressive weight loss
  • Poor coat condition
  • Enlarged lymph nodes
  • Persistent fever
  • Pale gums and other mucus membranes
  • Inflammation of the gums and mouth
  • Skin, urinary bladder, and upper respiratory tract infections
  • Persistent diarrhoea
  • Seizures
  • Behavior changes, and other neurological disorders
  • Eye problems
  • Abortion of kittens or other reproductive failures

How easy is it for a cat to catch FeLV?

The virus can’t survive outside of the host cat’s body for longer than a few hours under normal household conditions. Cats typically need to be exposed to the virus for a prolonged and repeated period of time to become infected. For this reason, cats kept in groups are particularly at risk.

Image of a cat for Vets Now article on feline immunodeficiency virus
All your feline leukemia questions answered — click to open

Is feline leukemia contagious to dogs?

No, feline leukemia only affects cats and can’t be passed on dogs or any other animal.

Is feline leukemia contagious to humans?

No, humans aren’t at risk of contracting the virus.

Which cats are most at risk of contracting leukemia?

Although all cats are potentially at risk of catching the feline leukemia virus, some are most at risk than others. These include:

  • Outdoor cats
  • Unneutered males
  • Cats with other diseases, such as respiratory diseases, mouth diseases and abscesses
  • Cats exposed to infected cats for a prolonged period of time (for example if they live with an infected cat)
  • Cats bitten by an infected cat
  • Young kittens

Can kittens contract the feline leukemia virus?

Yes, kittens are particularly at risk of catching FeLV as older cats generally build up a degree of immunity over time. The virus also develops more quickly in young kittens compared to adult cats. Kittens contracting the virus from an infected mother before birth is one of the primary methods of infection. In many cases, kittens infected before birth do not survive as abortion is often a result of the infection.

You might also be interested in:


How can I find out if my cat has feline leukemia?

Your vet may be able to perform a blood test to check if your cat has the virus. However, the test isn’t completely reliable and false positives and negatives can result. Therefore, in some cases, your vet may recommend sending samples to a commercial laboratory who use a different test, in order to increase the reliability of the result. The test may need to be repeated in 30 days if the risk of infection is high. If your cat goes outside or lives with another cat that has the virus, your vet may recommend that the test be repeated more frequently. The best course of action will be decided based on your cat’s individual circumstances.

Treatment and prevention

Treatment for leukemia in cats

When treating a FeLV-positive cat showing signs of disease, your vet will typically treat the problems specific to the symptoms they are displaying (like prescribing antibiotics for bacterial infections, or performing blood transfusions for severe anaemia).

How do I care for a cat with feline leukemia?

Cats with FeLV should be kept away from other cats, including cats that live in the same house.

The best way to keep a cat with feline leukemia safe is to minimise the risk of infection. Do this by keeping them indoors at all times and avoiding foods that can contain bacteria, such as raw meat and eggs. Keeping them indoors also avoids the spread of infection to other cats.

You should take your cat to the vet for regular check ups and act quickly if you suspect they are unwell as they will need treatment as quickly as possible. Your vet may also discuss vaccinating against other viruses (keeping in mind that the FeLV vaccine won’t work after your cat has contracted the virus).

Is there a cure for cat leukemia?

Sadly, there is no cure for cat leukemia. The lifespan of a cat with feline leukemia will be typically be shortened, but some cats may live for years without any major complications as a result of the disease. However, it’s impossible to predict how long individual cats will live.

How do I prevent my cat from catching the feline leukemia virus?

Keeping health cats away from infected cats is essential. There is also a feline leukemia vaccination which can help protect cats against the disease, although it is not 100% effective in all cases.

It’s best to discuss with your vet whether the vaccine is suitable based on the risk to your cat and your individual circumstances.

One of my cats has leukemia, how do I protect my other cats?

The only way to protect healthy cats is to isolate the infected cat, making sure they don’t come into close contact in your house. Getting the healthy cats vaccinated against the disease may also offer some protection, although this is not guaranteed as the vaccination is not completely effective in all cases.

If you have multiple cats in a household where one has leukemia, there is a risk that the others could already be infected, so it’s important to get them tested for the disease.

It’s also vital that any cat that contracts the virus is neutered to avoid passing on the infection to their kittens.