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Pinworm Infection

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In the United States, pinworm infection, or enterobiasis, is the most common of all parasitic roundworm infections. It primarily affects school-age children. Because pinworm infection is spread mainly by children, it is found most often in family groups, daycare centers, schools, and camp settings.

Cause

Pinworm infection is caused by an intestinal roundworm called Enterobius vermicularis.

Pinworms are small, threadlike roundworms found primarily in the colon and rectum. The life cycle of the pinworm—egg, larva (immature stage), and mature worm—takes place inside the human body and requires from three to six weeks to complete.

The pinworm is the most common roundworm parasite in temperate climates—even in areas that have to good sanitation practices.

Pinworms enter your body when you swallow their eggs. One female pinworm may expel thousands of eggs into the environment. As the eggs are moist and rather resistant to drying, they can infect humans even after being distributed in dust for several days.

The female pinworm deposits her eggs in the area around your anus. You can expose yourself to the infective eggs by scratching the contaminated area. The eggs then attach to your fingertips and from there go into your mouth. When you swallow, the eggs travel to your intestines.

The eggs also may be scattered into the air from bed linen and articles of clothing. They are capable of clinging to surfaces such as bedding, clothing, toys, doorknobs, furniture, and faucets for up to 2 weeks.

Symptoms

Folklore is filled with fantastic descriptions of symptoms and abnormal behavior attributed to pinworm infection. In fact, many people have no symptoms at all. Of those who do, the symptoms are usually mild and barely noticeable.

The movement of egg-laden female worms from your anus to deposit their eggs will often produce itching around the anus or vagina. This itching may become very intense, interfere with sleep, and make you irritable.

Diagnosis

Your healthcare provider can diagnose pinworm infection by simply finding the eggs. The most common way to collect the eggs involves swabbing the anal area with the sticky side of a piece of transparent cellophane tape. Your healthcare provider will then put the tape on a slide and look for the eggs under a microscope.

Treatment

If your healthcare provider prescribes medicine for this condition, everyone who lives in your house should take it, regardless of whether they have symptoms. Medicines, such as mebendazole or pyrantel pamoate, are the most useful in treating pinworm infection.

To relieve the intense itching that often happens with pinworm infection, your healthcare provider may also prescribe a soothing ointment or cream.

Because of the strong probability that children will be reinfected outside the home, in a daycare setting for example, major efforts to eliminate the eggs from the home are of little help.

Prevention

Some of the ways that you and your children can prevent becoming infected or reinfected with pinworms include

  • Bathing after waking up
  • Washing night clothes and bed sheets often
  • Washing your hands routinely, particularly after using the bathroom or changing diapers
  • Changing underwear every day
  • Avoiding nail biting
  • Avoiding scratching the anal area

Research

Researchers supported by NIAID are conducting basic and clinical research on the prevention, control, and treatment of a variety of parasitic diseases, including some caused by parasitic roundworms.

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Last Updated April 15, 2014