pinworm roundworm, Enterobius vermicularis, worldwide in distribution and the most common source of worm infestation of humans in the United States. Children are more commonly infested than adults. Adult pinworms inhabit and mate in the cecum of the large intestine and adjacent areas. When mature females become gravid they migrate down the colon and out onto the skin around the anus where they lay about 10,000 eggs and then die. Such movements cause intense anal itching. The eggs are infective within a few hours and are easily spread by the hands to the mouth, most often through touching contaminated household objects or food supplies. If infective eggs are swallowed the young worms hatch in the duodenum and migrate to the cecum. Development from ingested egg to gravid female requires 2 months. The most prominent symptom of the disease resulting from pinworm infestation, called enterobiasis, is anal itching, particularly at night; restlessness and insomnia are common, and sometimes gastrointestinal symptoms such as abdominal pain, nausea, and diarrhea, are also present. Since reinfection is a major problem, enterobiasis is treated by the following of strict hygienic measures, including careful cleansing of hands, body, and bed linens. Often, all members of the household must be treated for the disease. Pinworms are classified in the phylum Nematoda , order Oxyuroidea, family Oxyuridae.

Pinworm (Enterobiasis)

What Is the Pinworm’s Life Cycle?

What Are the Signs and Symptoms of Pinworm Infection?

How Do Doctors Diagnose and Treat Pinworm Infection?

How Do People Prevent Pinworm Infection?

Resource

Pinworm, or enterobiasis (en-ter-o-BY-a-sis), is a common intestinal infection caused by the Enterobius vermicularis parasite. It causes anal itching, and it is often spread by children to schoolmates or family members.

KEYWORDS

for searching the Internet or other reference sources

Gastrointestinal system

Infestation

Nematodes

Pinworm, or Enterobius vermicularis (en-ter-O-be-us ver-mik-u-LAY-ris), is a common and highly contagious* intestinal parasite. An estimated 200 million people worldwide, including 40 million people in North America, are infected. Pinworm is especially common in children, with a general infection rate of about 20 percent. Pinworms are small worms, usually less than 1 cm in length, and they resemble light-colored pieces of thread.

* contagious

means transmitable from one person to another.

What Is the Pinworm’s Life Cycle?

People become infected when they unknowingly swallow microscopic pinworm eggs. The pinworm eggs pass through the digestive tract, where they hatch in the small intestine into a larval* stage. Pinworm larvae then travel from the small intestine to the large intestine, where they attach to the intestinal wall. About two to six weeks after the eggs have been swallowed, adult female pinworms migrate from the large intestine to the rectum, where they exit from the anus to lay numerous eggs on nearby skin. The adult pinworms then return to the large intestine, where they usually die, but the new eggs become active within a few hours and remain active for up to three weeks.

* larva

is an intermediate stage in a worm’s life cycle between egg and adult.

Egg laying can cause itching in the infected person’s anal area, and pinworm eggs can be transferred from fingers to clothing, bedding, towels, toilets, and other objects in the environment. When people handle objects that have become contaminated with pinworm eggs, they may inadvertently touch their fingers to their lips afterward and swallow the new eggs, allowing the pinworm life cycle to begin again.

What Are the Signs and Symptoms of Pinworm Infection?

The most common symptom is anal itching, but most people with pinworms show no symptoms at all. Because female pinworms usually lay their eggs at night, this is when itching can be most intense, and it may interfere with sleep or may cause restless sleep. Sometimes, anal itching is so minor that it is not recognized as a symptom. In females, pinworms can migrate to the vagina, causing itching and vaginal discharge.

How Do Doctors Diagnose and Treat Pinworm Infection?

Diagnosis Pinworm infections are diagnosed if doctors find adult female worms or eggs around the anus. Doctors (or parents) place adhesive tape on the skin in the anal area, usually in the morning as egg laying occurs overnight. When the tape is removed and viewed under a microscope, eggs or worms stuck to the tape are visible.

Treatment When infection is confirmed, treatment is started. A single dose of prescription medication is given, sometimes with a follow-up dose two weeks later. Because of the contagious nature of pinworm infection, usually everyone in the household is treated. Reinfection is common and treatment may have to be repeated.

How Do People Prevent Pinworm Infection?

Proper personal hygiene can help prevent pinworm infections. It is important to wash hands after going to the bathroom and before eating. Bathing and changing underwear regularly are also useful. Despite such precautions, however, reinfection is common, particularly in children.

See also

Ascariasis

Trichinosis

Worms

Resource

The U.S. National Institute of Allergy and Infectious Diseases posts a fact sheet about pinworm and other parasitic roundworm diseases at its website. http://www.niaid.nih.gov/factsheets/roundwor.htm

pin·worm / ˈpinˌwərm/ • n. a small nematode (family Oxyuridae, class Phasmida) that is an internal parasite of vertebrates.

pinworm (pin-werm) n. see threadworm.