Feline Leukemia Virus
Feline Leukemia (FeLV) was first identified in 1964. The virus is known to cause both suppression of the immune system and the development of neoplastic (cancer) diseases. Immune suppression results in a cat susceptible to secondary diseases such as respiratory infections, anemia, mouth infections, skin disease and reduced wound healing. Neoplastic diseases may include tumor formation such as lymphoma or leukemia.
It is important to understand that cats may respond in a variety of ways following exposure to FeLV. About 30% of exposed cats have a persistent infection which develops into FeLV-related diseases. Most of these cats die within 3 years of infection. It is known though some cats may resist the infection and develop no disease. Some cats may be carriers with the virus lying hidden and showing no clinical signs. These cats may potentially expose and infect other cats.
Transmission is by direct contact. The virus is shed from cat to cat in tears, nasal secretion, and saliva. Sharing a common food and water source is a common route of transmission. Neonatal infections may occur by transmission between the female and kittens by crossing the placenta or mammary glands during nursing. The virus is not stable in the environment and becomes inactive in less than 2 hours in a dry environment.
ELISA (enzyme-linked immunosorbent assay) is the preferred initial screening test for FeLV using either blood, tears, or saliva. Previous feline leukemia vaccination does not interfere with FeLV testing. Maternal immunity does not interfere with testing as the ELISA detects antigen and not antibody. Since no test is 100% accurate a critical decision should not be based on a single test result. All ELISA (+) cats should be confirmed with an IFA test. The IFA correlates highly with FeLV infection in bone marrow cells and most (97%) IFA positive cats remain persistently infected.
Immunomodulating drugs may be used to improve the cat's own immune system and reduce clinical signs of infection. Treatment of secondary and opportunistic infections should be managed by symptomatic and supportive therapy. FeLV (+) cats can live for months to years. Appropriate management of FeLV (+) cats involves therapy for secondary infections and other FeLV-related diseases, reducing spread of the disease, and client education.
FeLV is controlled primarily by preventing exposure, appropriate husbandry practices, and vaccinations. It is recommended that new cats should be tested before being introduced to the household to prevent exposure of other cats. Cats housed alone indoors are considered a low risk for FeLV infection while outdoor cats and carriers are considered high risk. Vaccination of all cats is recommended.