Dogs are like children - they can get sick anywhere - and in order to keep them as long as possible, it is important to know what diseases are prevalent in dogs, what symptoms to look out for, and how to prevent the dog from infecting them. Eight canine diseases affect puppies of all ages and breeds in all states. Since dogs can get these diseases in a dog park, groom or shelter, it is important to always keep an eye on the puppy and call a veterinarian if his behavior seems suspicious or if he starts to show unusual symptoms.