Feline Leukemia and Feline Immunodeficiency Virus                    

Feline leukemia (FeLV) and feline immunodeficiency (FIV) infections are major causes of illness, cancer and death in cats. They affect cats by lowering their immune defenses, leaving them vulnerable to other infections. They are incurable, contagious from one cat to another, and can be fatal. Up to 15% of sick cats are infected with one or both of the viruses. But even seemingly healthy cats may harbor infection and spread viruses to other cats. In some cats, signs of disease may not become apparent until weeks, months or even years after they first become infected with FeLV or FIV. Kittens and juvenile cats are most susceptible to infection.

Transmission of FeLV and FIV is only from cat to cat, with no evidence of spreading to humans. FeLV is present in the saliva, urine and blood of infected cats. It is spread by direct and usually prolonged contact with other infected cats from behaviors like grooming and sharing food and water bowls as well as litter boxes. It can also be spread from an infected mother cat to her kitten through the milk or grooming. FIV is transmitted most commonly from breeding and fighting, not from casual contact with other cats. Rarely will FIV be spread from an infected mother cat to her kitten.

Clinical signs of both Felv and FIV infection can include weight loss, weakness, loss of appetite, swollen lymph nodes, discharge from the eyes and nose, diarrhea, fever, sore gums and mouth, or ataxia.

Diseases caused by both FeLV and FIV include anemia, upper respiratory tract infections, eye disorders, gum and mouth infections, chronic abscesses, chronic skin infections, fungal infections, toxoplasmosis and lymphoma. FeLV can also cause leukemia and fibrosarcomas.

Detection. A blood test that can be run in the hospital is used to detect FeLV and FIV infection in cats. A positive test means the cat may have FeLV or FIV. Since no test is 100% accurate, a confirmatory test is recommended. If a cat tests positive for both tests, it should be retested in two months. 

Guidelines for testing are:

·                     Whenever cats are sick, regardless of age, negative results of previous tests, and FeLV vaccination status.

·                     When they are about to be adopted, regardless of age. Cats should be tested before being introduced into a multiple-cat household to prevent exposing other cats in the household. If there are no other cats, FeLV/FIV status of the new cat should be known if the owner should adopt another cat or should the cat escape outdoors and expose other cats.

·                     If the cat had possible exposure to FeLV/FIV recently (e.g. bite wound) and the test is negative, it should be retested in 60 days because the virus may not be present in the blood stream early in the infection.

·                     If the FeLV/FIV status is unknown. Infected cats may show no signs of disease and may infect other cats.

·                     When they are exposed, or potentially exposed, to cats of unknown FeLV/FIV status (e.g. cats that go outdoors unsupervised) regardless of whether they have been vaccinated against FeLV.

·                     When they are about to be vaccinated for FeLV. FeLV vaccines should not be given to positive cats.

Treatment. Unfortunately there is no successful cure available for FeLV or FIV. Depending on the disease the cat has, with proper supportive care FeLV and FIV infected cats can be treated and live a long life.

Prevention. Preventing exposure to infected cats remains the single best way to prevent FeLV/FIV infection. FeLV vaccine is recommended for cats that are not restricted to a closed, indoor environment; it is most important for kittens less than 1 year of age. FeLV vaccine is not recommended for cats older than 1 year of age if they are kept strictly indoors. At risk, feline leukemia negative cats should initially be vaccinated twice at a 3-4 week interval and then tested and vaccinated annually. The present FIV vaccine is not recommended. The efficacy of the vaccine to all strains of FIV is unknown and FIV vaccinated cats test positive on present screening tests, making it difficult to determine if the cat is truly FIV positive or is a vaccinated cat.