Pinworm Infection (Enterobiasis)

What is pinworm infection?

This infection is caused by a small, white intestinal worm called Enterobius vermicularis (EN-ter-O-be-us ver-MIK-u-lar-is), which is about the length of a staple and lives in the rectum of humans. While an infected person sleeps, female pinworms leave the intestines through the anus and deposit eggs on the surrounding skin.

What are the symptoms of a pinworm infection?

Itching around the anus, disturbed sleep, and irritability are common symptoms. If the infection is heavy, symptoms may also include loss of appetite, restlessness, and insomnia. Symptoms are caused by the female pinworm laying her eggs. Most symptoms of pinworm infection are mild, and many infected people have no symptoms.

Who is at risk for pinworm infection?

Pinworm is the most common worm infection in the United States. School-age children, followed by preschoolers, have the highest rates of infection. In some groups nearly 50% of children are infected. Infection often occurs in more than one family member. Adults are less likely to have pinworm infection, except mothers of infected children. Institutional settings, including day care facilities, often harbor cases of pinworm infection.

How is pinworm infection spread?

Pinworm eggs are infective within a few hours after being deposited on the skin. They can survive up to 2 weeks on clothing, bedding, or other objects. Infection is acquired when these eggs are accidentally swallowed.

How is pinworm infection diagnosed?

If pinworms are suspected, transparent adhesive tape or a pinworm paddle (supplied by your health care provider) are applied to the anal region. The eggs adhere to the sticky tape or paddle and are identified by examination under a microscope. Because bathing or having a bowel movement may remove eggs, the test should be done as soon as you wake up in the morning. The exam may require several samples for diagnosis. Since scratching of the anal area is common, samples taken from under the fingernails may also contain eggs. Eggs are rarely found during lab examinations of stool or urine. At night, the adult worms can sometimes be seen directly in bedclothes or around the anal area.

How is pinworm infection treated?

With either prescription or over-the-counter drugs. You should consult your health care provider before treating a suspected case of pinworm. Treatment involves a two-dose course. The second dose should be given 2 weeks after the first.

What if the pinworm infection occurs again?

The infected person should be treated with the same two-dose treatment. Close family contacts should also be treated. If the infection occurs again, you should search for the source of the infection. Playmates, schoolmates, close contacts outside the house, and household members should be considered. Each infected person should receive the usual two-dose treatment. In some cases it may be necessary to treat with more than two doses. One option is four to six treatments spaced 2 weeks apart.

How can I prevent pinworm infection?

Measures such as cleaning and vacuuming the entire house or washing sheets every day are probably not necessary or effective. Screening for pinworm infection in schools or institutions is rarely recommended. Children may return to day care after the first treatment dose, after bathing, and after trimming and scrubbing nails.

This fact sheet is for information only and is not meant to be used for self-diagnosis or as a substitute for consultation with a health care provider. If you have any questions about the disease described above or think that you may have a parasitic infection, consult a health care provider.

Division of Parasitic Diseases
National Center for Infectious Diseases
Centers for Disease Control and Prevention

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