The Feline Leukemia Virus (FeLV) is an illness that is passed between cats through direct contact by bodily fluids. Many times it is passed from cat to kitten during nursing. FeLV can be very deadly to kittens, and about a third of kittens who have FeLV die from it.
When adopting a new cat, you should have them tested for this disease right away and vaccinated against it, if they haven’t been already. A cat that has FeLV can exhibit a wide range of symptoms, including anemia, loss of appetite, weight loss, diarrhea, blood in the stool, and lethargy. If your cat exhibits any of these symptoms, see your veterinarian immediately.