Several internal parasites (frequently referred to as worms) make dogs their victims. The most common ones are the roundworms that infest puppies at some time in their young lives and tapeworms that can be a cause for worry when flea infestations get high. Evidence of roundworms and tapeworms can be easily seen without the aid of a microscope, but other worms are rather difficult to diagnose. Occasionally, adult whipworms are seen in the stool when the infestation has already caused some debilitation or weight loss in the dog. Early diagnosis of the presence of the species of intestinal parasite is extremely important, for not all worms respond to the same treatment. Therefore, stool samples should be immediately taken to the veterinarian for microscopic examination if worms are suspected. Most veterinarians include the stool check as part of the annual health examination.