I don't know what you mean by "diseases". They are often hard to separate from health problems that come from poor care and ignorance rather than occurring out of the blue. There are vitamin and mineral deficiencies that result in bone and metabolic disorders, many types of bacteria that cause infections, parasites that cause organ damage, dehydration that can result in kidney failure, stress that lowers the immune system response, all kinds of things. Whether or not you consider such things "diseases" or not isn't clear from your question. A contagious disease such as rabies, IBD (boids), viruses, etc. are sort of a different thing and we probably don't have a list of these for you.