Overview of FeLV
Feline leukemia virus (FeLV) infection is responsible for more deaths among cats than any other infectious disease. The virus affects domestic cats and occurs in some wild felines as well.
There are three main types of feline leukemia virus: FeLV-A, FeLV-B, and FeLV-C. FeLV-positive cats can be infected with one, two, or all three types:
- FeLV-A occurs in all FeLV-infected cats and causes severe immunosuppression (weakened immune system).
- FeLV-B occurs in about 50% of all FeLV-infected cats and causes more neoplastic disease (i.e., tumors and other abnormal tissue growths) than cats infected only with FeLV-A.
- FeLV-C occurs in about 1% of FeLV-infected cats and causes severe anemia.
After the initial infection, the virus replicates in the tonsils and pharyngeal lymph nodes (the pharynx is the muscular tube in the neck). Then it spreads via the bloodstream to other parts of the body, especially the lymph nodes, bone marrow, and intestinal tissue, where it continues to replicate. Viremia, the presence of virus in the blood, usually shows up 2 to 4 weeks after the initial infection.
FeLV is one of the most devastating feline diseases worldwide. In the United States, FeLV infects about 2% to 3% of all cats.