Feline leukemia virus (FeLV) is a retroviral infection that is a common concern in our pet cats and in feral cat populations. It is a disease that results in an impaired immune system that can effect many body systems (for example causing anemia, mouth inflammation, development of lymphoma, reproductive problems). FeLV is transmitted from cat to cat most often through saliva (including bite wounds or shared grooming), but transmission also may occur through blood, nasal secretions, feces, and milk. The prognosis for infection and development of secondary complications is poor with patients generally becoming ill in months to several years.

All kittens are checked for FeLV status at one of their initial kitten exams. Older cats are checked if they have been exposed or if recently adopted and their history is not known. It is baseline health information for all feline patients. If the patient is negative, the recommendation from the American Association of Feline Practitioners is to recheck the patient in 2-3 months after no potential exposure to the virus. If negative on a second test, it is much more likely that the patient is truly negative. It is possible to get false negative results, so depending on the patient and history sometimes it is very important to check again.

Currently, there is not a specific treatment for FeLV infection. These patients should be housed indoors, have appropriate vaccines, have good nutrition and proper health checks at least every 6 months. Some of the secondary issues caused from the virus can be treated with medication, but the concern still exists for repeat problems since the virus can not be cleared.

Fortunately, there is a vaccine to help protect against infection, which all cats that are exposed to other cats should receive. Cats and kittens receive a series of two boosters 3-4 weeks apart to start and then receive a yearly booster. FeLV vaccines do not interfere with testing a cat for the virus in the future. Thankfully, the virus is unstable in dry conditions and is susceptible to common disinfectants. This means that it can be cleaned up easily in dry environments (as most home environments are), so for example, a new cat could safely be housed in an area formerly holding a FeLV positive cat after a few days and cleaning.

Leukemia virus infection is a very serious condition, which is why we, as veterinarians, want to make sure we know an individual cat's status in order to offer the best care and recommendations. It is a concern for a single cat and for cat populations worldwide, and as our knowledge base grows and better awareness develops, hopefully we can continue to provide better care for our feline friends.