Feline Leukemia Virus (FeLV)

Updated: 6/30/23
Outdoor cats playing or fighting.


Feline leukemia virus (FeLV) is a viral infection that attacks a cat’s immune system, weakening the ability to fight off other infections. The prevalence of FeLV in cats has decreased over the past 30 years thanks to widespread testing and increased awareness of the disease. The development of a vaccine against FeLV has played a more minor role in the decrease in infection rates.

Unfortunately, there is no cure for FeLV, but it can be managed so that the remainder of your cat’s life is normal.

Risk Factors

There is increased risk for the disease among outdoor cats, unneutered males, and cats with other diseases (especially respiratory disease, mouth diseases, and abscesses). Cats infected with FeLV may transmit the virus to other cats through social behavior such as mutual grooming as well as through a shared litter box or feeding dish. An infected mother cat may also transmit the disease to her kittens, either before they are born or while they are nursing.


During the early stages of infection, there may be no signs of illness. Over time, an infected cat’s health may deteriorate, or she may experience alternating periods of illness and relative health. Signs may include:

  • Loss of appetite
  • Weight loss
  • Enlarged lymph nodes
  • Fever
  • Inflammation of the gums (gingivitis) and mouth (stomatitis)
  • Bite wound abscesses
  • Infections of the skin, urinary bladder, and upper respiratory tract
  • Diarrhea
  • Seizures, behavior changes, and other neurological disorders
  • Cancer, especially lymphoma


Feline leukemia virus is diagnosed with a blood test. Your veterinarian likely will recommend the test when you adopt your cat and again if vaccination is recommended.


While there is no cure for FeLV, some infected cats can live without major illness for several years with proper nutrition and routine veterinary care, including vaccinations to prevent upper respiratory disease. Veterinarians may treat specific problems such as prescribing antibiotics for bacterial infections or frequent dental cleaning to control oral and gum inflammation. Infected cats should be kept indoors to reduce the risk of other infections and to prevent spreading the virus to other cats.


The only way to protect cats from FeLV is to prevent exposure to FeLV-infected cats, so keeping cats indoors is critical. Cats should be tested for FeLV before being introduced to a home with other cats, and only FeLV-negative cats should be added to the household to prevent the spread of the disease. A FeLV vaccine is available, but it is not considered a core vaccine. Your veterinarian can help you decide if it’s necessary for your cat.

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Internal Medicine

About Internal Medicine at AMC AMC’s specialists in Internal Medicine are certified by the American College of Veterinary Internal Medicine. Areas of this specialty service include: Endocrinology Gastroenterology Hematology Immune

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