Feline Leukemia (FeLV) FAQs

What is feline leukemia?

The feline leukemia virus — or FeLV — is a virus that affects cats all over the world. It can weaken a cat’s immune system and can predispose him or her to developing other conditions such as cancer.

How is feline leukemia transmitted?

There are a number of ways that cats can get FeLV, including from an infected mother at birth, by nursing from an infected mother, or from other cats through a bite or mutual grooming. Rarely is FeLV acquired through the shared use of litter boxes and feeding dishes, given that the virus does not last long outside of a cat’s body. So, take comfort in knowing that spread of the virus via the environment is rare.

The cats at greatest risk of infection are those who:

  • Live with infected cats or with cats of unknown infection status
  • Are allowed outdoors unsupervised, where they may be bitten by an infected cat
  • Are kittens born to an infected mother

What is the life expectancy of a cat who is FeLV positive?

While a cat with FeLV might be prone to getting infections and may have a shorter life expectancy than one without the virus, a FeLV-positive cat can still lead a very happy life.

What are the symptoms of FeLV?

During the early stages of infection, it is common for cats to exhibit no signs of disease at all. However, over time — anywhere from weeks to years — the cat's health may progressively deteriorate, or be characterized by recurrent illness interspersed with periods of relative health. Signs of such deterioration can include:

  • Persistent fever
  • Loss of appetite
  • Progressive, often slow weight loss
  • Persistent diarrhea
  • Poor coat condition
  • Enlarged lymph nodes
  • Inflammation of the gums (gingivitis) and mouth (stomatitis)
  • Infections of the skin, urinary bladder and upper respiratory tract
  • Pale gums and other mucous membranes
  • Eye conditions
  • Neurologic abnormalities

Being FeLV-positive most often leads to a state of immunodeficiency in which the cat cannot fight off diseases or infections, as an uninfected cat would. In addition to the signs of deterioration listed above, some cats may have significant blood abnormalities, such as anemia or cancerous cells in the blood. In fact, FeLV is the most common cause of cancer in cats.

How is FeLV diagnosed?

There are two types of blood tests that are commonly used when testing cats for the virus. Both detect a protein component of the virus as it circulates in the cat’s bloodstream.

Most shelters and vets start with an ELISA (enzyme-linked immunosorbent assay) test, which can be performed in a vet’s office. Cats can test positive within a few weeks after exposure, although the exact time that the virus can be detected in the blood can be variable. Negative screening test results are highly reliable. However, if the results are negative but recent infection cannot be ruled out (e.g., contact with other cats), testing should be repeated a minimum of 30 days after the last potential exposure.

Testing positive on the ELISA means that the virus is circulating in the cat's blood; it does not mean that the cat will be permanently infected. It is possible for some cats to fight off the infection.

To find out if it is a persistent infection, a test called IFA (indirect immunofluorescent antibody assay) can be sent to a lab. If this test is positive, the cat is considered positive for FeLV and always will be. If it is negative, there is a chance the cat can fight off the infection (although recent research shows that the virus may just be dormant until a physiologic stressor allows it to circulate again). If the ELISA test is positive and the IFA is negative, the cat is deemed “FeLV discordant” and both the ELISA and the IFA should be repeated in six weeks.

If you adopt a cat with FeLV, check with your veterinarian — or inquire at the shelter where you adopted your cat — to make certain the FeLV diagnosis was made based on appropriate testing. Positive test results should be confirmed, especially in asymptomatic and low-risk cats.

Untested cats, or confirmed infected cats, should be kept strictly indoors to reduce the risk of exposure to illness or infectious disease and to prevent transmission of the virus to other cats. Also, if you have cats who do not have the virus, you should keep them separate from your cat who is confirmed FeLV-positive in order to keep the disease from spreading within your home.

Is there a cure for FeLV?

To date, no curative treatment exists for feline leukemia. However, some FeLV-positive cats can live without major disease complications for many years with routine preventive care, minimal stress and avoidance of secondary infections. Although FeLV-positive cats often respond well to treatment, therapy for infections or other illnesses should be conducted early and aggressively because of the cat’s compromised immune system.

If you have adopted one of these special little friends, you’ll want to be sure to keep an eye out for the signs mentioned above. Mostly, however, simply enjoy your new companion.