Feline leukemia virus (FeLV) is a retrovirus that infects cats and is one of the most common infectious diseases in cats, affecting between 2 and 3% of all cats in the United States. FeLV can be transmitted from infected cats when the transfer of saliva or nasal secretions is involved, and it can also be transmitted from an infected mother cat to her kittens, either before they are born or while they are nursing. The virus invades various cells of the cats immune system and blood-forming tissues, leading to a moderate to severe suppression of the immune system, which means that the infected cat is less able to defend itself against a wide range of infections that would not normally cause a problem in healthy cats. FeLV can also cause various blood disorders and may lead to a state of immune deficiency that hinders a cats ability to protect itself against other infections.
Cats infected with FeLV can serve as sources of infection of FeLV-A, which is responsible for the immunosuppression characteristic of the disease. FeLV can be categorized into four subgroups, with FeLV-A being the most common. FeLV-B causes an additional increase in the incidence of tumors and other abnormal tissue growths, while FeLV subgroups C and T are less common.
Symptoms of FeLV include pale gums (anemia), decreased appetite, weight loss, unthrifty coat (poorly groomed, dry, brittle), inflamed gums and mouth (gingivitis and stomatitis), fever, enlarged lymph nodes, chronic diarrhea, and chronic skin, eye, respiratory, or urinary tract infections. FeLV is diagnosed by conducting a simple blood test called an ELISA, which identifies FeLV proteins in the blood. Cats at greatest risk of FeLV infection are those that may be exposed to infected cats, either via prolonged close contact or through bite wounds. Cats living with infected cats or with cats of unknown infection status, cats allowed outdoors unsupervised where they may be bitten by an infected cat, and kittens born to infected mothers are at higher risk. Indoor-only cats have a very low risk of contracting FeLV.
