Threadworm disease is the condition caused by infestation of the rectum and large intestine with threadworms (Enterobius vermicularis), the common pinworm. The hallmark is itching around the anus, typically worse at night when the female worms emerge to lay eggs, leading to disturbed sleep, irritability, and in children sometimes secondary bacterial infection from scratching. The disease spreads with remarkable ease in families and schools because the microscopic eggs survive on bedding, clothing, and dust and are swallowed after hand contact. It is diagnosed by detecting eggs on perianal skin and treated with medicines such as mebendazole for the whole household. Strict hygiene for several weeks prevents the reinfection cycle.