Enterobius vermicularis ova in routine cervicovaginal smears. Light and scanning electron microscopic observations

From 1971 through 1980, four Papanicolaou smears containing pinworm (Enterobius vermicularis) eggs were found among approximately 220,000 routine smears examined at the University of Texas Medical Branch at Galveston. The highest number of ova counted on one slide was 420. Typical light microscopic features of the eggs included elongated oval shapes with flattening of the ventral sides and double-contoured shells folded at one end. The background in three smears showed massive acute inflammation. A scanning electron microscope study of one case revealed that the ova had a relatively smooth surface with an invaginated area at one end.