Of course there are minor differences, but these are far outweighed by the remarkable similarities. The differences can give important clues about diseases and how they might be treated - for instance, if we knew why the mouse with muscular dystrophy suffers less muscle wasting than human patients, this might lead to a treatment for this debilitating and fatal disorder. Vitamins and hormones identified by animal experiments were found to have similar functions in people. Such similarities mean that studies in animals have led to the medicines which have transformed the treatment of many diseases during this century. Over one third of the veterinary medicines that are used to treat animals are the same as, or very similar to, those used to treat human patients.
Most human diseases exist in at least one other species.
Illnesses such as cancer, heart failure, asthma, rabies and malaria are suffered by many species and can be treated in much the same way.