A type of cancer caused by the feline leukemia virus, a retrovirus which affects only a small percentage of freely roaming or domestic cats. The feline leukemia virus is genetically and morphologically similar to murine leukemia virus, from which it presumably evolved several million years ago.
About 1–5% of healthy-appearing wild or freely roaming domestic cats have lifelong (persistent) infections. These carrier cats shed the virus in urine, feces, and saliva. The principal route of infection is oral. Infections occurring in nature are usually inapparent or mild, and 95% of such cats recover without any signs of illness. Mortality due to a feline leukemia virus infection occurs mainly among persistently infected cats and at a rate of around 50% per year.
There is no treatment that eliminates the virus. Supportive or symptomatic treatment may prolong life for weeks or months, depending on the particular disease manifestation. All cats should be tested for the presence of the virus prior to putting them in contact with feline leukemia virus-free animals. Healthy-appearing or ill infected cats should not be in intimate contact with noninfected cats, even if the latter have been vaccinated. Feline leukemia virus vaccines are available and should be administered annually, although they should not be considered a substitute for testing, elimination, and quarantine procedures. See also Leukemia; Retrovirus.
