Threadworm eggs. Light micrograph of a cervical smear containing four threadworm eggs (oval with dark centres) surrounded by normal squamous cells from the cervix. Threadworm or pinworm (Enterobius vermicularis) primarily affects people living in temperate regions. The female adult threadworm lives in the intestines and lays eggs around the anus, which cause itching. Scratching may transfer eggs from fingers to mouth, or to the vagina as here. Treatment involves good hygiene and the use of anthelmintic drugs. Cervical smear tests are routinely carried out to look for abnormalities in cells of the cervix, which may indicate cancer. Magnification: x550 when printed 10cm wide.