Threadworm in the cervix. Light micrograph of a cervical smear showing a threadworm emerging from its egg (at centre). In the background are normal cells of the cervix. Threadworm, sometimes called pinworm, is the small parasitic worm Enterobius vermicularis. It primarily affects children living in temperate regions. The female adult threadworm is about 1 centimetre long, occurring in the intestines and eggs are laid around the anus causing itching. Scratching may transfer eggs from fingers to mouth, or into the vagina as here. Treatment involves good hygiene and the use of anthelmintic drugs. Stained with Papanicolaou. Magnification: x16 at 35mm size.