Not all canine parasitic infections cause obvious worms crawling around in a dog's feces, but the gastrointestinal disturbances are fairly similar for all parasites. Parasite infections are diagnosed through a dog's stool samples, but most of the time parasites are too small to be seen in feces without a microscope. If you suspect your dog has a parasitic infection, consult with your dog's veterinarian so treatment can be started as soon as possible.
A whipworm infection results from a dog eating contaminated soil or feces. The owner does not notice worms in the feces, but the dog experiences symptoms of diarrhea, weight loss, declining health and possibly rectal bleeding. If whipworms are suspected, it can take several stool samples to make a diagnosis. Hookworms are also a parasitic dog infection that requires a microscope for diagnosis. The symptoms are the same as a whipworm infection. Ingestion is one way hookworms cause infection to a dog, but the larvae of these parasites can also penetrate the skin. Hookworms can be transmitted to humans.
Tapeworms are the most common parasites found in a dog's feces. The dog becomes infected by ingesting a flea carrying the infective stage of the tapeworm or by eating an infected rodent or rabbit. The tapeworm carried by fleas is Dipylidium caninum and the tapeworm carried by rabbits and rodents is called Taenia pisiformis. Owners may notice segments of the tapeworm that look like rice in the dog's feces or on hairs around the dog's anus. If the head of the tapeworm disconnects from the small intestines, the entire worm may appear in feces or vomit. These worms are around 8 inches long. Diphyllobothrium is a rare tapeworm dogs become infected with after eating certain types of raw fish. The Diphyllobothrium can grow to 20 meters.
If a dog has a roundworm infection that goes untreated, there is a risk of the parasite population growing large enough in the small intestines to cause fatal intestinal blockage. Symptoms of a roundworm infection include abdominal pain, bloating and diarrhea. An adult worm in the dog's feces is large enough for an owner to see, but the eggs in the feces are microscopic. These worms can migrate to the dog's lungs leading to pneumonia.
Treatment and Prevention
Approximately 85 percent of puppies are infected with roundworms, so puppies need an oral deworming medication at 4, 6 and 8 weeks and then a follow up visit around 12 weeks. Monthly heartworm prevention is available through your dog's veterinarian to prevent roundworm infections. Anytime you suspect a parasitic infection based off your dog's symptoms, bring a fresh sample of feces that's less than 24 hours old to your veterinarian. The sample can be refrigerated, but not frozen. Some parasites, such as one-celled protozoans, are treated with a antimicrobial that works like antibiotics, but most dogs with parasite infections will be dewormed through oral or injectable medications and then brought in for a follow-up visit. A dog with a tapeworm infection may require flea treatments, as well as flea prevention mechanisms like collars, powders or topical ointments.