What is FeLV (Feline Leukemia Virus)?

FeLV (Feline Leukemia Virus) is a retrovirus that infects the bone marrow and various tissues in cats, and can cause anemia, bone marrow suppression, immunodeficiency, and predisposition to lymphoma and other tumors. Unlike FIV, FeLV spreads more easily through close, prolonged contact between cats — sharing food and water bowls, mutual grooming, and from mother to kittens during pregnancy or nursing — without requiring a bite wound.

Infected cats may go through a regressive phase of infection (in which the body is able to contain the virus) or a progressive phase, in which the virus remains active and causes disease over time. Signs are nonspecific and varied: weight loss, lethargy, recurrent fever, pale mucous membranes (a sign of anemia), recurrent respiratory and skin infections, gingivitis, and, in advanced stages, tumors.

As with FIV, there is no cure for FeLV, but early diagnosis through a blood test allows owners to prevent transmission to other cats (by keeping the infected cat separated from healthy cats) and to manage the cat's quality of life with regular veterinary follow-up. A vaccine against FeLV is available and recommended for cats at risk of exposure, especially those with outdoor access or living with cats of unknown status. See a veterinarian to test any new cat before introducing it to other cats in the household, and whenever there are signs of anemia, recurrent infections, or weight loss.