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Feline leukemia virus (FeLV)


Feline leukemia (FeLV), a widespread, incurable virus that typically suppresses a cat’s immune system, is the most common cause of cancer in cats. FeLV is species-specific, so humans and dogs are not at risk.


Research indicates that feline leukemia virus is highly contagious among cats of all ages. Among cats, it is spread by saliva, urine, and blood. The disease is spread from cat to cat through bites, mutual grooming, and sharing food or water dishes and litter boxes. A cat can also pass the virus along to its kittens in a number of ways before they are born. Current research indicates that it does not affect humans or other species. 

  • Anemia, lack of pink or red color in the gums
  • Weight loss
  • Recurring or chronic illness
  • A progressive weakness
  • Lethargy, fever, diarrhea
  • Breathing difficulty
  • Yellow color in the mouth and/or the white of the eyes
Diagnosis and treatment

Avoiding exposure with infected cats and updating vaccinations are the best tools of preventive medicine. FeLV is highly contagious, so it is important to have your cat vaccinated if it could be exposed to other cats. The American Association of Feline Practitioners recommends all kittens receive the vaccine.

Infected cats may harbor the illness for several years with no signs of illness. Over time, they may lose weight, become depressed, or develop a fever. Their coats often deteriorate, and they may develop skin, bladder, or upper respiratory infections.

An accredited veterinarian can diagnose the disease by conducting a simple blood test called an ELISA.

Your veterinarian will talk to you about the importance of maintaining a balanced diet. Also, he or she will ask you about your cat’s lifestyle and look for ways to reduce stress, both of which are key to managing your cat's disease.

Infected cats should be kept indoors so they won’t spread the virus. If you have multiple cats, have all of them tested, vaccinate any that are not infected, and consider housing infected cats separately.

Your veterinarian can determine the best program for your cat. Although some cats are able to eliminate the virus on their own and develop immunity, many others die as a result of cancer or opportunistic infections. Cats infected with the virus live an average of three years.

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