Whipworms – Tiny threadlike worms found in the large intestine of dogs. They can cause bloody diarrhea and colitis if left untreated. Microscopic eggs are passed in the stool of infected dogs. Your dog may ingest them by licking his feet after walking through the soil where the eggs have been deposited.

Roundworms – Large, long worms found in the stomach and small intestines of infected animals. They cam cause a "pot belly", especially in young animals, loose stool, and weight loss. Animals can contract these worms through the mother's placenta before being born. Adult pets become infected by ingesting eggs or by ingesting rodents infected with dormant larvae. If people accidentally ingest the microscopic eggs through contact with infected soil or pet's feces, the worms can migrate through the human body. One serious result is blindness if the larva settles in the eye.

Hookworms – These tiny parasites suck the blood of their host by attaching to the small intestinal lining. This parasite is transmitted through the colostrums or first milk to newborn pets or through skin penetration. Untreated, this parasite can cause a severe anemia, poor appetite, coughing and a generalized loss of condition. If a person happened to have contact with soil where the larvae are developing, the microscopic larva could potentially penetrate through the skin. There can be migration of the larva causing an eruption in the human skin.

Tapeworms – A long flat segmented worm transmitted by ingesting rabbits or rodents or, more commonly, by ingesting fleas. There can be mild weight loss. The appearance of worm segments around the rectum of infected pets or on furniture is how they are usually diagnosed. The segments can look like small pieces of rice or sesame seeds. Flea control must be a part of the treatment program to prevent re-infestation. The segments passed from dogs and cats are not infective to humans. Humans get tapeworms from other sources.