If your cat gets all its shots regularly, feline leukemia should never be a problem. Along with rabies and distemper, it's part of the standard shots given during vaccination. The most serious thing about feline leukemia among unvaccinated cats is the fact that it's contagious. Transmission comes through an exchange of blood, urine, or saliva. Feline leukemia doesn't usually kill cats. It only makes them less resistant to infections and cancers that do. Symptoms will vary from cat to cat, but generally include lethargy and loss of appetite. If you have your kitten vaccinated when it's nine or ten weeks old and give it regular booster shots when the veterinarian recommends, feline leukemia should never be a problem.