Pinworms

Pinworms (Enterobius vermicularis) are parasitic worms about the size of a staple that infect the intestines. They are sometimes referred to as seatworms or threadworms.


Causes/associated factors
Pinworms only affect humans. Pinworm eggs enter the digestive system and hatch in the small intestine. The larvae move to the large intestine, where they survive for two to three weeks by attaching their heads to the bowel wall. When an infected person sleeps, a mature female pinworm travels from the large intestine to the rectal area where she lays her eggs and usually dies.
Children are the most likely to contract pinworms. School-aged children are the most susceptible, followed by preschoolers. Caregivers of infected children are also at increased risk of infection, as well at those who live in institutional settings. The pinworm is the most common parasite in children who live in temperate climates.


Transmission
Pinworms are contagious. An infected person can spread pinworms by scratching the infected area and then touching food, toys, toilet seats, bathtubs or other items. In turn, another person can become infected by eating the contaminated food or touching the contaminated object and then touching his or her own mouth. You can also become infected when handling infected clothing or linens by swallowing the eggs. An infected person can reinfect himself or herself in these same ways. Pinworms live for about two months in the intestines and the eggs can survive at room temperature outside the body on clothing, linens, toys and other objects for up to two weeks. The infection can spread as long as either the pinworms or eggs exist.

Signs/symptoms
It can take two to four weeks for symptoms to develop. Many people infected with pinworms have mild symptoms or don't even know they're infected. The most common symptom is itching and irritation of the rectal area after falling asleep at night or waking up in the morning. Girls may also have itching in the vaginal area. Sometimes, the itching is intense and embarrassing. Children may have disturbed sleep or wake up crying. Sometimes, pinworms appear on bowel movements. Although uncommon, severe pinworm infections can cause loss of appetite, restlessness and insomnia.

Diagnosis
If you think your child has pinworms, the doctor may ask you to examine your child's anal area with a flashlight a few hours after he or she falls asleep and again first thing in the morning. (Taking a bath or having a bowel movement can remove the eggs, so it's important to do the test at the right time.) Look for tiny white, threadlike worms that may be moving. (They may be about ¼ to ½ inch long.) Of course, wash your hands thoroughly when you're through to prevent infecting yourself. The doctor may suggest looking for pinworms several days in a row.
The doctor may also recommend the "Scotch tape test." Place a small piece of transparent tape or a pinworm paddle (available at your doctor's office) against your child's anal area a few hours after he or she has fallen asleep or first thing in the morning. Remove the tape or paddle, place it in a small plastic bag or container and wash your hands thoroughly. Take the sample to your doctor's office, where it will be examined for pinworm eggs under a microscope. You may need to obtain several samples for an accurate diagnosis. The same test can be used to detect pinworms in adults. Contact your doctor for specific instructions.

Eggs can lodge under the fingernails if an infected child scratches his or her anal area, so the doctor may also want samples from underneath your child's nails.


Treatment
Over-the-counter pinworm treatments are available, but consult your doctor before selecting one for your child or yourself (especially if you're pregnant and think you may have pinworms). Your doctor may recommend a prescription medication, such as pyrantel pamoate, mebendazole or albendazole. With this medication, a two-dose course of treatment may be necessary (one starting two weeks after the first). The doctor may also recommend that household members who have symptoms be treated as well. Antipruritic creams or ointments applied around the anus may help relieve anal itching.
If you or your child have a pinworm infection:

Stay home for 24 hours after the first dose of medication.
Bathe (preferably in the shower) first thing in the morning to remove any eggs around the anal area.
Open bedroom curtains or blinds -- pinworm eggs are sensitive to sunlight.
Change underwear, pajamas and bedding often, including after treatment. To kill the eggs, boil these items or wash them in hot water in the washing machine.
Wash your hands often, especially before eating or preparing food and after using the toilet.
Reinfection with pinworms is common and a second round of treatment may be necessary. Contact the doctor if the symptoms return.


Complications
Pinworms don't usually cause other health problems. Continual scratching may cause a secondary skin infection, however. Rarely, pinworms migrate to various sites throughout the body -- such as the appendix, female genital tract, urinary tract or the abdominal cavity -- and cause inflammation.

Pregnancy-specific information
Treating pinworms with medication is not recommended during pregnancy.

Senior-specific information
Growing older is not a risk factor for contracting a pinworm infection.

Prevention
To prevent a pinworm infection:
Wash bedding and towels in hot water and dry them on a heat setting in the dryer.
Keep fingernails trimmed and clean and discourage nail biting.
Avoid scratching the anal area.
Wash your hands often, especially before eating or preparing food and after using the toilet or changing diapers. Teach your children to do the same.