Cat Leukemia (Feline Leukemia Virus)

PetMD Editorial
Written by:
PetMD Editorial
Published: August 1, 2008

Feline Leukemia Virus Infection (FeLV) in Cats

Feline leukemia virus (FeLV) is a disease that impairs the cat's immune system and can cause cancer. This viral infection is responsible for too many deaths in household cats, affecting all breeds. The good news is that it is completely preventable. The bad news is that most cats with FeLV live only a few years after their diagnosis.

Symptoms and Types

Cats with FeLV may not show any signs, even for years. Some of the more common symptoms of feline leukemia include:

  • Anemia
  • Lethargy
  • Progressive weight loss 
  • Susceptibility to infection
  • Persistent diarrhea
  • Infections of the external ear and skin and poor coat condition
  • Fever (seen in about 50 percent of cases)
  • Wobbly, uncoordinated or drunken-appearing gait or movement
  • Generalized weakness
  • Inflammation of the nose, the cornea, or the moist tissues of the eye
  • Inflammation of the gums and/or mouth tissues (gingivitis/stomatitis)
  • Lymphoma (the most common FeLV-associated cancer)
  • Fibrosarcomas (cancer that develops from fibrous tissue)


Cat leukemia is usually contracted from cat-to-cat transmission (e.g., bites, close contact, grooming and sharing dishes or litter pans). It can also be transmitted to a kitten at birth or through the mother's milk. Kittens are much more susceptible to the virus, as are males and cats that have outdoor access.


If your cat is ill, your veterinarian will first rule out other infections such as bacterial, parasitic, viral or fungal. In addition, nonviral cancers need to be ruled out.

A simple blood test is available to determine whether your cat has FeLV.  


Unfortunately, 85% of cats with FeLV die within three years of diagnosis.

There is no treatment or cure for feline leukemia. Treatment is directed at symptoms and often includes steroids, blood transfusion and supportive care when necessary. Some medications have shown promise in treating feline leukemia, including antivirals used in human AIDS treatment.

If your cat has no symptoms when she is diagnosed with FeLV, there is no treatment necessary apart from good at-home care.

If your cat is ill, feline leukemia makes it difficult for the cat’s body to respond to treatment. Your veterinarian will prescribe medication to treat the symptoms. Your cat may be hospitalized for severe secondary infections, low red-blood cell count, weight loss with muscle loss, or other symptoms as your veterinarian sees fit. In these cases, he will be kept under hospital care until his condition stabilizes. Emergency treatment, such as blood transfusions, is sometimes required.


Living and Management

You will need to monitor your cat for symptoms of infection and keep in touch with the veterinarian regarding follow-up treatment and testing. Treating minor signs of illness is especially important in a cat with known feline leukemia virus. Due to the virus, her body may be unable to appropriately respond to minor infections and other illnesses.

Cats with feline leukemia virus may have a normal lifespan if other illnesses can be prevented.

Keep FeLV-infected cats indoors and separated from healthy cats to prevent virus exposure and FeLV transmission. Good nutrition is important, as is controlling any secondary bacterial, viral or parasitic infections.



Keeping infected cats separated (and quarantining them) is the only way to 100 percent prevent cat leukemia in healthy cats. There is a vaccine against FeLV; however, it is important to test your cat before initial vaccination, as he  may already be infected. Even if you intend for your new kitten to be strictly indoors, most veterinarians will recommend including the FeLV vaccine in his kitten booster series. Cats can escape from the house and lifestyles change. It is important for your cat’s health that he be protected, and the vaccine poses very minimal risk.

A cat with feline leukemia should be kept strictly indoors and away from uninfected cats.  

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