Feline Leukemia Virus (FeLV)

Last updated: 2020-12-21
Document type: Information Sheet
Species: Feline

Feline leukemia virus (FeLV) is an incurable infectious disease. Testing for and management of FeLV in a shelter setting can be complicated; therefore, it is important for shelters and rescue organizations to understand this disease and to develop a policy to address it based on their mission, their available resources, and their housing and re-homing strategies.

What is FeLV?

FeLV, or Feline leukemia virus, is a contagious, viral disease of cats. In addition to causing leukemia, it has been associated with various other types of cancer, anemia, and immune suppression leading to increased susceptibility to various infectious diseases. Although cats may clear initial infection, there is no cure for persistent infection and it is ultimately fatal.

Who gets FeLV?

It appears that cats are the only species susceptible to infection with FeLV. Kittens are at significantly higher risk for contracting the disease than adult cats.

How is FeLV spread?

FeLV is most commonly spread from mother to offspring, transplacentally or more likely via nursing or grooming. Transmission is possible via the saliva of infected cats, either directly or by contaminated articles such as food and water dishes. FeLV can also be present in other secretions such as urine or feces, but this is less common.  Airborne spread is not a concern. FeLV is not very durable in the environment. It is inactivated by most commonly used disinfectants.

How is FeLV Diagnosed?

Blood tests are available for screening for FeLV. The most commonly used test is the ELISA test, which looks for viral antigen (protein) in the blood. This is available as an in-house kit. It is imperative to follow the instructions for whatever test is used exactly, as the consequences of both a false positive and a false negative test are potentially severe. Staff members performing the test should be trained and periodically evaluated.

Strategies for FeLV testing

see our FAQ: "Why are some shelters no longer testing all cats for FeLV and FIV?"

What is the prognosis for cats with FeLV?

FeLV infection can cause various types of cancer, especially lymphoma and, as the name implies, leukemia. It can also cause anemia and deficiencies of other blood cell lines, as well as causing general immunosuppression that makes the cat vulnerable to numerous infectious diseases. Acutely infected kittens may have several years with a good quality of life before developing signs of disease, and some individual cats may live much longer. However, 50% of infected cats living in multiple cat households will die within two years of contracting the disease, and that number increases to 80% after three years.

Treatment consists of good nourishment, protection from stress, and management of secondary conditions. There is no treatment that has been shown to be effective in curing FeLV infection.

Should cats be vaccinated for FeLV?

A vaccine is available for FeLV. It is not 100% effective, so there is still some risk of introducing an FeLV positive cat into an environment with vaccinated cats. The vaccine is not recommended for cats that are at very low risk for contracting the disease, such as strictly indoor cats. This vaccine is generally not recommended in a shelter except under unusual circumstances. Rather, the new owner and their veterinarian should decide whether the vaccine is appropriate for the individual circumstance.

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