Veterinarians identify worms by inspecting a stool sample under a microscope, as PetMD explains. Once identified, the veterinarian prescribes the proper deworming medication to treat the worms.
There are several types of intestinal worms, including roundworms, hookworms, whipworms and tapeworms, as reported by PetMD. They all typically cause signs such as diarrhea, poor hair coat, weight loss and vomiting.
Roundworms can pass through the uterus or the milk from mother to puppies, which means that a large majority of puppies are born infected, states PetMD. The larvae are able to encyst in the tissues of an animal, and they become resistant to deworming medications. Active worms in the intestinal tract pass eggs into the dog's stool, which then leads to other dogs becoming infected by coming into contact with the contaminated stool.
Tapeworms are transmitted through the ingestion of fleas, as PetMD explains. Dogs pass small tapeworm segments in their stools that resemble grains of rice. This makes them easily identifiable without the assistance of a microscope.
Whipworms are not frequently seen in the stool, as PetMD details. They reside in the large intestines and produce very few eggs, making them difficult to identify. Often, multiple stool samples are required before veterinarians can make a positive whipworm diagnosis.
Hookworms are also transferred from mother to puppies, notes PetMD. These worms feed off the blood in the small intestinal walls. Since they draw blood from an animal, they carry the risk of causing anemia and even death in small puppies.