A roundworm is any of a large group of parasitic worms with cylindrical, unsegmented bodies, distinct from the flatworms. Species that trouble humans include the giant intestinal roundworm Ascaris lumbricoides, hookworms that attach to the gut wall and feed on blood, and threadworms common in children. Infection spreads through contaminated soil, food, or water carrying eggs or larvae, and heavy infestations cause malnutrition, anaemia, and stunted growth in children. Food safety connects directly: unwashed vegetables grown in contaminated soil, undercooked pork carrying Trichinella larvae, and raw freshwater fish with anisakis worms all transmit roundworm infections. Thorough washing, proper cooking, and sanitation break the cycle.