How does FeLV infect a cat?
Feline leukemia goes through several stages after entering a cat's eye and nose membranes, says William D. Hardy Jr., V.M.D., of Cornell University. It first travels to lymph nodes in the throat, where it begins to reproduce, infecting the cat's white blood cells. At this stage, the cat could fight off the disease if its immune system is strong enough; about 40 percent of exposed cats are able to withstand the virus. Otherwise, the infected blood cells transport the virus to the spleen and intestinal tissue, as well as to other lymph nodes.
Eventually the virus enters the bone marrow and contaminates the cat's growing blood cells. Circulating blood then carries the virus to the salivary glands, respiratory cells and urinary tract. About 56 days after invading its host, the virus becomes present in the cat's saliva and urine, and can be passed to other cats.