Some other problems related to their health are hairballs, worms (such as tapeworms, roundworms, and hookworms), vomiting, flea, conjunctivitis, cat flu, ear mites, feline stress, feline infectious peritonitis, feline immunodeficiency virus, feline leukemia virus, Lyme disease, abscess, and toothache. You may notice some general indications that your cat is not feeling well such as changes in its behavior, appetite or elimination, as well as changes in its appearance.