Feline Leukemia Virus
Feline Leukemia (FeLV) is a viral disease transmitted either from mother to kittens via milk or the placenta or from cat to cat via saliva and urine. It is often referred to as a “disease of friendly cats” since close contact is required for transmission. This includes grooming, and sharing food or water bowels.
The outcome of exposure to the virus varies widely. This is dependent on both viral and host factors. The viral strain, dose and length of exposure affect the chances of infection as does the cats age, immune system and concurrent disease status. Young cats are most susceptible to infection. Once infected, cats either clear the infection completely or remain infected. For cats that do not clear the infection there are two courses the disease may take. One is for the virus to become latent in some cells during which time all routine FeLV tests will be negative. This infection can be reactivated in times of stress. The other course is for cats to become immediately and persistently viremic. Tests on these cats will come up positive and they are infectious to other cats.
Clinical signs of FeLV infection are extremely variable, usually nonspecific and depend on the type of disease process present. These processes can be either neoplastic (as the name implies) or non-neoplastic. The two most common forms of cancer caused by the virus are lymphoma (lymphosarcoma) and leukemia. Non-neoplastic disease is typically due to immunosuppression and includes gastrointestinal disease, upper respiratory disease, skin problems, and dental disease. Often cats initially present for not eating well, fever, weight loss, lethargy or depression.
Testing for Feline Leukemia virus is readily available and easily performed with a blood sample. Testing is recommended on any at risk cats (outdoors, new cats being introduced into environment), sick cats and kittens. A single positive response indicates exposure and retesting in 12 weeks is recommended to confirm persistent infection. There is a vaccine available and it does not interfere with testing.
There is no treatment for FeLV infection but good preventative health care can allow these cats to lead long healthy lives. They do best indoors in a closed environment to prevent infecting other cats and limit their exposure to other infectious agents. It is recommended that infected cats have exams every 6 months to monitor weight and catch any problems early. They typically take longer to clear infections so it is recommended to begin treatment sooner and continue longer than would be done with a non infected cat. They should have year round parasite prevention and deworming as well as good dental care. These cats should also be spayed or neutered.
There is a vaccine available to protect from Feline Leukemia virus. It is typically recommended for cats that are at risk - living in a house hold with a known infected cat or access to the outdoors. This vaccine has been implicated in association with vaccine associated fibrosarcomas (a very rare but potentially deadly tumor) so it is typically only used in cats that are at risk as stated above. Vaccine protocols should be discussed with your veterinarian and established on your cats particular needs.