Glossary

Roundworm

A common intestinal worm that often infects puppies, frequently from the mother, and can pass to people, especially children.

Also called: Toxocara canis, ascarid, ascarids, puppy worms, worms in puppies

Roundworms, mainly Toxocara canis, are pale, spaghetti-like worms that live in the intestines. Puppies often get them before birth or through the mother's milk, and dogs of any age can pick up eggs from soil or feces. Infected puppies may have a pot belly, a dull coat, poor growth, vomiting or diarrhea, and may pass worms in stool or vomit.

Roundworm eggs can infect people, particularly young children who play in dirt, and may cause illness, so hand-washing and prompt cleanup matter. Because eggs survive in the environment for a long time, prevention is routine.

Vets schedule deworming for puppies and test adult stool. A fecal test confirms which parasite is present, and common deworming products differ, so ask a veterinarian instead of buying a general one.

Last reviewed November 8, 2026

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Related terms

Fecal test A laboratory check of a dog's stool for parasite eggs and organisms such as roundworm, hookworm, whipworm and Giardia. Hookworm A small intestinal worm that attaches to the gut wall and feeds on blood, causing anemia in puppies, and can burrow into human skin. Whipworm A parasite of the large intestine whose eggs stay in soil for years and which can cause chronic, mucus-covered diarrhea in dogs. Tapeworm A flat intestinal worm, usually caught by swallowing an infected flea, that sheds rice-like segments seen near a dog's tail.