Pinworms. Caused by common GI parasitic worm, with itching of anus. Also see Enterobius Vermicularis and Parasites Enterobiasis programs.AnusEncyclopedia Entry for Enterobiasis :Enterobiasis - Pinworm infection - Enterobius vermicularis (intestinal nematode)Encyclopedia Entry for Enterobiasis :Enterobiasis (Pinworm infection). Source of disease: Enterobius vermicularis