five recognized subtypes; the most common infectious disease in domestic Felidae; another common slow virus disease of cats also in the Retroviridae family is feline immunodeficiency virus (FIV). Symptoms of FeLV may overlap with FIV, depending on potential complicating secondary processes (e.g., secondary bacterial invaders, neoplasia) or physiologic response to chronic slow virus infection (e.g., anemia). Virus shedding occurs in saliva, tears, and excrement. Viruses have poor environmental survival, so close cat contact is needed for agent transfer. Cogrooming and cat bites are common transmission routes. Clinical picture varies from progressive debilitation leading to death, to asymptomatic carriers (bone marrow sequestration). Affected cats may be anemic, icteric, have fading kittens, abortion, infertility, lymphadenopathy, polyuria and polydipsia, diarrhea, lethargy, and death. Vaccine licensed for use.