Microscopy

The eggs of Enterobius vermicularis measure 50-60 µm by 20-30 µm , are elongate-oval and slightly flattened on one side.  They are usually partially-embryonated when shed.  Enterobiasis can be diagnosed by applying cellulose tape to the anus of a suspect patient, especially in the morning before the patient's first bowel movement.  Eggs will adhere to the tape and can be seen microscopically.

A	B

A:  Eggs of E. vermicularis in a cellulose-tape preparation.
B:  Eggs of E. vermicularis in a wet mount.

C	D

C:  Egg of E. vermicularis in an iodine-stained wet mount from a formalin concentrate.  Image contributed by the Kansas State Public Health Laboratory.
D:  Eggs of E. vermicularis viewed under UV microscopy.

Adult males of E. vermicularis measure up to 2.5 mm long by 0.1-0.2 mm wide; adult females measure 8-13 mm long by 0.3-0.5 mm wide.  Adult males have a blunt posterior end with a single spicule; females possess a long pointed tail.  In both sexes, there are cephalic expansions.

E

F:  Adult male of E. vermicularis from a formalin-ethyl acetate (FEA) concentrated stool smear.  The worm measured 1.4 mm in length.  Note the cephalic expansions on the anterior end (to the right) and the blunt posterior end.  The spicule was withdrawn into the worm in this specimen and not visible.  Image contributed by the Centre for Tropical Medicine and Imported Infectious Diseases, Bergen, Norway.

F	G

F:  Anterior end of an adult female of E. vermicularis, recovered from a colonoscopy.  Image contributed by the South Carolina Department of Health and Environmental Control, Bureau of Laboratories.
G:  Posterior end of the worm in Figure F. Note the long, slender pointed tail.

Adults of E. vermicularis in tissue sections stained with hematoxylin and eosin (H&E).

H	I

H:  Cross-section of a male E. vermicularis from tissue, stained with H&E.  Notice the presence of the alae (blue arrow), intestine (red arrow) and testis (black arrow).
I:  Cross-section of an adult female E. vermicularis from the same specimen shown in Figure H.  Note the presence of the alae (blue arrow), intestine (green arrow) and ovaries (black arrows).

J	K

J:  Cross section of an adult female E. vermicularis stained with H&E, recovered during a colonoscopy.  Note the prominent alae (blue arrow) and the presence of eggs (yellow arrow). Image contributed by Sheboygan Memorial Hospital, Wisconsin.
K:  Longitudinal section of an adult female E. vermicularis from the same specimen as Figure J.  Note the presence of many eggs.