Feline leukemia virus (FeLV) is one of the most serious diseases to which your cat can be exposed. Due to strong efforts by the veterinary community through vaccinating and testing, the prevalence of this disease has declined significantly since its discovery 50 years ago. However, we still see it enough that you should be concerned about your cat’s risk.
Feline leukemia has been called the “Friendly Cat Disease” (versus FIV (make this a hyperlink to the FIV page) which is called the “Aggressive Cat Disease”) because for cats to contract this virus they must have prolonged close contact with each other. The virus is spread through the saliva (and less commonly through urine and feces), so grooming, sharing water and food bowls, sharing litter boxes, and occasionally fighting put your cat at risk. Mothers can even pass this virus to their kittens through the placenta or through their milk.
Feline leukemia is a cat-only virus. Once this virus is picked up by the cat, there are several paths it may take. Some cats clear the virus and never have a problem. Other cats may not show any signs of illness, but are able to spread the virus to other cats. Cats that can’t clear the virus experience the worst symptoms. These cats may develop cancer, such as leukemia and lymphoma, develop anemia and/or become prone to secondary infections from weakened immune systems. Sadly, cats with FeLV that take this path only live to be about 2-3 years of age.
We recommend testing all kittens by 12 weeks of age to know their FeLV/FIV status. Since the virus can take a different path in each individual cat, we want to test each kitten in the litter. It is not safe to assume if one is negative that the rest of the litter will be negative.
Cats that go outside, or cats that live with cats that go outside, are at highest risk for contracting this virus. We recommend testing them for FeLV annually to make sure they have not become infected. For cats that are indoor only and aren’t exposed to cats that go outdoors, we recommend testing every other year. We also recommend retesting any cats who are sick to make sure FeLV is not the cause of the illness.
Unfortunately there is no treatment for the feline leukemia virus. Your cat’s best mode of protection is prevention by vaccination. All kittens should receive the FeLV vaccine series to help support their immature immune systems. If they remain at high risk (i.e. go outside, live with cats that go outside, live with a person who fosters cats, live at a house with a lot of stray cats outside), they should continue to receive the vaccine annually.