Feline leukemia virus is one of the most dangerous infectious
diseases affecting cats today. It's spread from cat to cat
through tears, saliva, urine, or droppings. Even if your cat
becomes infected, there's a slight chance that its immune system
will take care of the disease. There's no medical cure. An
infected cat could exhibit any of a dozen or more symptoms,
including depression, weight loss, diarrhea, or constipation.
Feline leukemia virus also lowers the cat's resistance to other
diseases, any of which could prove fatal in its weakened state.
Prevention is the best course of action. Kittens should be
vaccinated when they're nine or ten weeks old, with a booster a
month later. The vaccines are not 100 percent effective, so even
cats who've had their shots should be kept away from infected
animals.