Human: How can I tell if my cat has feline leukemia? Assistant: 
If your cat is showing signs of illness, such as weight loss, decreased appetite, difficulty breathing, or swelling around the face and neck, you should take them to a veterinarian for further evaluation. Feline leukemia virus (FeLV) is a common cause of these symptoms in cats. Your vet will be able to test your cat for FeLV and determine whether they have it.