Feline leukemia is a virus that damages a cat's immune system, making it unable to fight off infections and disease

Feline leukemia virus (FeLV) is a contagious disease that weakens a cat's ability to stay healthy. The virus attacks white blood cells — the cells that normally protect against infection — and can lead to anemia (low red blood cell count), cancer, and other serious illnesses. A cat with feline leukemia may seem fine at first, but over time the virus makes the immune system fail, allowing other infections to take hold.

Unlike human leukemia, which is a cancer of blood cells, feline leukemia is caused by a virus. It spreads between cats through saliva, urine, feces, and blood. A mother cat can pass it to her kittens before birth or through nursing. Once a cat is infected, the virus stays in the body for life, though some cats can clear the infection in the early stages if their immune system is strong enough.

Key Takeaways

  • Feline leukemia is spread through saliva, urine, feces, and blood, so indoor cats are at lower risk than outdoor cats.
  • A blood test called an ELISA or FeLV antigen test can detect the virus, and results usually come back within days.
  • There is no cure for feline leukemia, but treatment focuses on managing symptoms and keeping your cat comfortable for as long as possible.
  • Vaccination before exposure can prevent infection, and keeping a cat indoors reduces the chance of catching the virus.
  • A cat with feline leukemia can live months to years depending on how quickly other infections develop and how well symptoms are managed.

How cats catch feline leukemia

Feline leukemia spreads when an infected cat's saliva, urine, or feces comes into contact with another cat's mouth, nose, or a wound. Sharing food bowls, litter boxes, or grooming each other can transmit the virus. Bites during fights are a common route of infection, which is why outdoor cats and cats in multi-cat households face higher risk.

Indoor cats that live alone or only with other indoor cats have very low risk of exposure. Kittens born to infected mothers can be infected before birth or through nursing. A cat cannot catch feline leukemia from humans, dogs, or other species — only from other cats.

Signs your cat may have feline leukemia

Early signs are often vague and easy to miss. Your cat may seem tired, lose interest in food, or have a dull coat. Some cats develop a fever or swollen lymph nodes (small lumps under the neck, armpits, or back legs). Over time, as the immune system weakens, other infections take hold.

Later signs depend on what secondary infections develop. Your cat might have chronic diarrhea, vomiting, mouth sores, respiratory infections, or skin problems. Some cats develop cancer, particularly lymphoma (a cancer of immune cells). Weight loss, pale gums, and difficulty breathing can also occur. Because these signs are not specific to feline leukemia — they can mean many different things — a blood test is the only way to know for certain.

How doctors test for feline leukemia

Your veterinarian will draw a small blood sample and send it to a lab for testing. The most common test is called an ELISA (enzyme-linked immunosorbent assay), which detects proteins from the feline leukemia virus in the blood. Results usually come back within a few days. Some veterinary clinics have in-house tests that give results in minutes, though these are less sensitive than lab tests.

If the first test is positive, your vet may recommend a second test called a Western blot to confirm the result, especially if your cat has no symptoms. This is because some cats can clear the virus on their own in the first few weeks of infection, and a second test helps distinguish between cats that are truly infected and those that have already fought off the virus.

Treatment and managing feline leukemia

There is no cure for feline leukemia. Treatment focuses on managing symptoms, fighting secondary infections, and keeping your cat comfortable. Your veterinarian may prescribe antibiotics for bacterial infections, antiviral medications to slow the virus, or medications to manage pain and nausea. Regular blood work helps monitor your cat's condition and catch new problems early.

Good nutrition, a stress-free environment, and regular veterinary care extend your cat's quality of life. Some cats live months after diagnosis; others live several years. The outcome depends on how quickly secondary infections develop, how well your cat's body responds to treatment, and your ability to manage symptoms at home. Your vet can discuss what to expect based on your cat's age, overall health, and test results.

Preventing feline leukemia in other cats

If you have a cat with feline leukemia, keep it indoors and separate from other cats if possible. The virus spreads through close contact, so a cat living alone poses no risk to other households. If you have multiple cats, discuss with your vet whether the infected cat can safely live with the others or whether separation is necessary.

A feline leukemia vaccine can prevent infection in cats that have not been exposed. Kittens typically receive the vaccine at 8 and 12 weeks of age, with a booster at one year. Outdoor cats or cats in multi-cat households benefit most from vaccination. Cats that are already infected cannot be vaccinated, as the vaccine will not help them. Your vet can test your cat before vaccination to make sure it is not already infected.

When to call your veterinarian

Contact your vet if your cat shows signs of illness: loss of appetite, lethargy, vomiting, diarrhea, difficulty breathing, or mouth sores. If you know your cat has been exposed to a cat with feline leukemia, call your vet to discuss testing and next steps. If your cat has already been diagnosed with feline leukemia and develops new symptoms or seems to be declining, let your vet know so they can adjust treatment or discuss comfort care options.

If you are considering adopting a cat, ask the shelter or rescue whether the cat has been tested for feline leukemia. Many shelters test all cats before adoption. If you are introducing a new cat to a household with an infected cat, your vet can advise on safe ways to do this or whether it is better to keep them separate.

Frequently Asked Questions

Can a cat with feline leukemia live with other cats?

It depends on the situation. If the other cats are vaccinated and the infected cat is kept indoors with minimal contact, some cats can coexist. However, the safest approach is separation to prevent transmission. Your vet can assess your specific household and recommend the best option.

How long does a cat with feline leukemia usually live?

There is no set timeline. Some cats live months after diagnosis; others live several years. Lifespan depends on the cat's age, overall health, how quickly secondary infections develop, and how well symptoms respond to treatment. Your vet can give you a better sense of what to expect based on your cat's test results and condition.

Is feline leukemia painful?

The virus itself is not painful, but secondary infections and complications can cause discomfort. Mouth sores, for example, can make eating painful. Your vet can prescribe pain relief and other medications to keep your cat comfortable. Discuss quality of life with your vet if your cat's condition declines.

Can I catch feline leukemia from my cat?

No. Feline leukemia only infects cats. You cannot catch it from your cat, and you cannot spread it to other people. You can, however, carry the virus on your hands or clothes to other cats, so wash your hands after handling an infected cat before touching other cats.

Should I test my cat for feline leukemia?

Testing is recommended for kittens before vaccination, for any cat showing signs of illness, and for cats that may have been exposed to infected cats. Indoor cats with no exposure risk may not need routine testing, but discuss this with your vet based on your cat's lifestyle and risk factors.