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.
Most worm infestations cause some or all of these symptoms: diarrhea, sometimes with blood in the stool, weight loss, dry hair, general poor appearance and vomiting, perhaps with worms in the vomitus. However, some infestations may cause few or no symptoms at all. In fact, some worm eggs or larvae remain dormant in the dog's body and activate only in times of stress. In the case of roundworms, it is only in the latter stages of pregnancy that the worm activates, infesting the soon to be born puppies. Several worms that infect dogs may also infect humans. Therefore, treatment and eradication of the worms in the environment is very important. Dog feces must be removed from the back yards if not daily, then at least weekly, appropriate vermicides are to be used under veterinary supervision, and the dog's feces should be checked frequently in persistent cases. One should not mix wormers and not use any wormer if the dog is currently taking any other medication, including heartworm preventative, without consulting the veterinarian.