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Enterobiasis, or pinworm infection as it is commonly called, is an intestinal infection caused by the parasitic roundworm called Enterobius vermicularis. The most common symptom of this irritating, but not particularly dangerous, disease is itching around the anal area.


Enterobiasis is also called seatworm infection or oxyuriasis. In the United States, enterobiasis is the most common worm infection, and some estimate that approximately 10% of the United States population is infected. Worldwide, approximately 200 million people are infected. Enterobiasis can affect people of any age, but is most common among children ages 5-14 and particularly affects those in the daycare setting.

Causes and symptoms

The disease is highly contagious and is caused by a parasitic worm called Enterobius vermicularis. The adult female worm is about the size of a staple (approximately 0.4 in [1 cm long] and 0.02 in [0.5 mm] wide) and has a pointed tip. The disease is transmitted by ingesting the eggs of the pinworm. These eggs travel to the small intestine where, after approximately one month, they hatch and mature into adult worms. During the night, the female adult worms travel to the area around the anus and deposit eggs in the folds of the anal area. A single female pinworm can lay 10,000 eggs and, after laying eggs, dies. The eggs are capable of causing infection after six hours at body temperature.
Significant itching in the anal region is caused by the movement of the adult worm as the eggs are deposited. When an individual scratches the anal region, the tiny eggs get under the finger nails and in the underwear and night clothes. Anything the individual touches with the contaminated fingers, for example, toys, bedding, blankets, bathroom door knobs, or sinks, becomes contaminated. The eggs are very hardy and can live on surfaces for two to three weeks. Anyone touching these contaminated surfaces can ingest the eggs and become infected. An individual can also become infected by inhaling and swallowing the eggs, for example, when the bedcovers are shaken.
Many individuals with enterobiasis exhibit no symptoms. When present, however, symptoms of the infection begin approximately two weeks after ingesting the pinworm eggs. The main symptom is itching around the anus. Because the itching intensifies at night, when the female worms comes to the anus to lay eggs, it often leads to disrupted sleep and irritability. Poor sleeping at night in small children can be related to pinworms. Occasionally, the itching causes some bleeding and bruising in the region, and secondary bacterial infections can occur. In females, the itching may spread to the vagina and sometimes causes an infection of the vaginal region (vaginitis). Enterobiasis usually lasts one to two months.


First, a physician will rule out other potential causes of the itching, such as hemorrhoids, lice, or fungal or bacterial infection. Once these have been ruled out, an accurate diagnosis of enterobiasis will require that either the eggs or the adult worms are detected. Rarely, the adult worms are seen as thin, yellowish-white threads, about 0.4 in (1 cm) long, in the stools of the infected person. Usually, an hour or so after the individual goes to sleep, the adult female worms may be seen moving around laying eggs if a flashlight is shone at the rectal area.
An easier method is to observe the eggs under the microscope. In order to collect a specimen for laboratory diagnosis, the physician may provide a paddle with a sticky adhesive on one side, or an individual may be instructed to place a piece of shiny cellophane tape sticky side down against the anal opening. The best time to perform this test is at night or as soon as the individual wakes up in the morning, before having a bowel movement or taking a bath or shower. The pinworm eggs will stick to the tape, which can then be placed on a specimen slide. When under a microscope in the laboratory, the eggs will be clearly visible.


In order to treat the disease, either mebendazole (Vermox) or pyrantel pamoate (Pin-X) will be given in two oral doses spaced two weeks apart. These medications eradicate the infection in approximately 90% of cases. Re-infection is common and several treatments may be required. Because the infection is easily spread through contact with contaminated clothing or surfaces, it is recommended that all family members receive the therapeutic dose. Sometimes a series of six treatments are given, each spaced two weeks apart. If family members continue to be infected, a source outside the house may be responsible.
To relieve the rectal itching, a shallow warm bath with either half a cup of table salt, or Epsom salts is recommended. Also, application of an ointment containing zinc oxide or regular petroleum jelly can be used to relieve rectal itching.


Pinworms cause little damage and can be easily eradicated with proper treatment. Full recovery is expected.

Key terms

Anus — The opening through which feces are eliminated.
Hemorrhoid — An area around the anus where veins become dilated and the tissue swells, causing itching and pain.
Rectum — The end of the large intestine in which feces collects for elimination through the anus.
Vaginitis — Inflammation of the vagina.


The disease can be prevented by treating all the infected cases and thus eliminating the source of infection. Some ways to keep from catching or spreading the disease include the following recommendations:
  • wash hands thoroughly before handling food and eating
  • keep finger nails short and clean
  • avoiding scratching the anal area
  • take early morning showers to wash away eggs deposited overnight
  • once the infection has been identified, and treatment is started, change the bed linen, night clothes, and underwear daily
  • machine wash linens in hot water and dry with heat to kill any eggs
  • open the blinds or curtains since eggs are sensitive to sunlight



Fauci, Anthony S., et al., editors. Harrison's Principles of Internal Medicine. New York: McGraw-Hill, 1997.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.


infection with nematodes of the genus Enterobius, especially E. vermicularis (the pinworm); called also oxyuriasis.

Pinworm infection does not produce the fatigue and loss of weight that characterize Ascaris infection; adult pinworms migrate to the anal region, usually at night, and deposit eggs, which cause irritation of the skin around the anus, leading to painful scratching and restless sleep. This irritation is the usual sign of the infection, although there may also be vague intestinal discomfort. Adult worms may appear in the feces, but the infection is transmitted by the eggs, which may be transferred to clothing, bedclothes, and toilet seats from the skin around the anus. A common method of detection is to apply clean adhesive tape to the rectal area immediately upon awakening. The tape can then be placed sticky side down on a glass slide. The health care provider will examine the slide under a microscope for evidence of infestation.

In scratching, the infected person is likely to collect the minute eggs on the hands and under the fingernails, and, until washing thoroughly, will shed the eggs on anything touched. The infection spreads to other persons when the eggs are carried to their mouths either by inhalation or on contaminated food, in beverages, or on hands. Widespread pinworm infection is explained by the fact that the eggs, which develop into mature worms only in a human body, can remain dormant but alive and infective for a considerable time in dust or air; they are not killed by most household disinfectants.

Enterobius vermicularis infection is treated by an anthelmintic such as mebendazole, piperazine, or pyrvinium. Equally important, instructions for disinfecting bedclothes and other material that may harbor eggs must be followed carefully to avoid reinfection and spread of pinworms to other members of the family.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.


Infection with Enterobius vermicularis, the human pinworm.
Farlex Partner Medical Dictionary © Farlex 2012


Infestation of the intestine with pinworms.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.


Infection with Enterobius vermicularis, the human pinworm.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012


Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005
References in periodicals archive ?
Of these diseases, enterobiasis is still the most common and its prevalence levels remain high (24).
Ectopic enterobiasis is an infrequent finding in clinical as well as diagnostic practice.
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[2.] Song HJ, Cho CH, Kim JS, Choi MH, Hong ST: Prevalence and risk factors for enterobiasis among preschool children in a metropolitan city in Korea.
Risk factors for ascariasis versus enterobiasis in residents of Cornwall, United Kingdom, 1995-2010 Risk factor Ascariasis, no.
Enterobiasis may also be acquired through surfaces that are contaminated with pinworm eggs (e.g.
Assessment of frequency, transmission, and genitourinary complications of enterobiasis (pinworms).
(including V cholerae) Giardiasis Amebiasis (Entamoeba histolytica) Leishmaniasis Tuberculosis Brucellosis Leptospirosis Echinococcosis (hydatid disease) Typhus (epidemic, endemic) Relapsing fever, tick and louse-borne Trachoma Intestinal helminth infections (ascariasis, enterobiasis, trichuriasis) Hookworm infection (ancylostomiasis) Tapeworm infection (taeniasis) Strongyloidiasis Sandfly fever Other arboviral fevers Dengue fever Boutonneuse fever Congo-Crimean hemorrhagic fever (CCHF) Korean hemorrhagic fever Rift Valley fever Viral hepatitis (A, B, C, D, E) Meningococcal meningitis Syphilis (endemic, Bejel) Anthrax Q fever Rabies Plague Malaria Onchocerciasis Schistosomiasis Dracunculiasis Hymenolepiasis