Enterobius vermicularis, commonly known as the pinworm, is a parasitic nematode that infects the large intestine of humans. The document describes the diagnostic structures of E. vermicularis by presenting an image of one of its fertilized eggs found in a fecal sample. The egg is oval shaped, measuring 50-60 μm by 20-40 μm, with a thin colorless shell. Diagnosis is usually made by detecting the eggs on cellophane tape pressed against the anal skin, as the female pinworms lay their eggs perianally. This causes itching and rash around the anus. The image was captured using light microscopy at 1000x magnification after preparing the fecal

1. Diagnostic Structures of
Intestinal Helminths:
Enterobius vermicularis
Authors: Javier Gutierrez Jimenez, J.A. Hernandez-Shilon, P. Ramirez-
Cobaxin
Citation: Javier Gutierrez Jimenez, J.A. Hernandez-Shilon, P. Ramirez-
Cobaxin. 2011. Diagnostic structures of intestinal helminths: enterobius
vermicularis.
Publication Date : June 2011

2. Introduction
The figure shows an Enterobius vermicularis (pinworm) egg found in a feces sample. G enerally the ovum measures 50 to 60 μm long
by 20 to 40 μm wide. The figure is of an embryonated ovum, flattened on one side, with a thin colorless shell.
Methods
Diagnosis of pinworm infection is usually based on the recovery of typical eggs by means of the transparent cellophane ("Scotch") tape
preparation. With tape held between the thumb and forefingers of both hands, the outward -facing adhesive surface is pressed against
the skin across the anal opening with even thorough pressure. The tape is then transferred to a glass microscope slide with the
adhesive surface downward in such a way as to firmly adhere to the slide. Because adult female pinworms live in the lower portion of
the intestinal tract, females often lay their eggs on the surface of the fecal mass or on the anal skin folds. As a result, the eggs are
not well mixed within the feces and usually will not be detected in routine stool examinations. We visualized the E. vermicularis ovum
shown here, however, in a fecal sample prepared using the iodine-stained direct smear method. After the preparation was analyzed
under light microscopy, the egg was photographed with a digital camera (Leica Microsystems) using an oil immersion objective (1,000x
magnification).
Discussion
E. vermicularis is a parasite of the large intestine of humans and is found primarily in young children. The ability of the organism to
persist for extended periods on fomites and in the external environment leads to rapid dissemination of the infection from child to
child and to adults. Infections are especially common in institutional settings. A gravid worm of this nematode migrates to the anus at
night and dies after laying eggs. This deposition of eggs is irritating and causes itching around the anal area, known as pruritus ani.
Adult females migrating out of the anus may enter the vagina and the uterus or fallopian tubes, where they die. Disintegration of the
dead worms and liberation of the eggs contained in the uterus result in an inflammatory response and granuloma formation about the
eggs in these sites.
References
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3. Fertilized Enterobius vermicularis egg found in feces
A fertilized Enterobius vermicularis egg found in
feces. The fecal sample was prepared using the iodine-stained direct
smear method.
American Society For Microbiology ©

4. Fertilized Enterobius vermicularis egg found in feces (Labeled view)
(Labeled view)
American Society For Microbiology ©