A pinworm is a short, skinny parasite — 5 to 10 millimeters long — that lives in the human colon (large intestine). Its proper name is Enterobius vermicularis. The female pinworm crawls out of the anus and lays her eggs on the skin. When the temperature is right (98° to 99°F), the eggs mature into an infectious form.
The eggs are then passed from person to person by the fecal-oral route: wiping or itching, followed by poor (or no) hand washing, allows pinworm eggs to collect on a person’s hands. The eggs are then transferred to sheets, clothes, carpets, toilets and bathroom fixtures, eating utensils and glassware, sandboxes, and so on, where they can be picked up by another person. They can also be passed directly from the hands of the host to the hands of another person. It is estimated that 40 million people in the United States have or have had pinworms.
Once a person ingests pinworm eggs, the eggs make their way to the small intestine, where they hatch. About a month later, they are ready to move toward the large intestine and repeat the cycle. The time from ingestion of the eggs to itching on the bottom is usually two to four weeks.
When the worms crawl out of the anus and deposit eggs on the skin, they cause itchiness. The classic indicator of pinworms is itching around the anus at night, right about bedtime. Girls can have vaginal itching as well because the worms can migrate for¬ward into the vagina. Pinworms can also be associated with behavioral changes, such as restlessness and irritability, in toddlers.
What can I do?
The worms are easily visible. If your child is complaining of itch¬ing, have him lie facedown with his bottom in the air. When you shine a light at his anus, you will see threadlike worms or small yellow egg sacks. If you see pinworms on your child, you should treat them medically. They will not go away on their own.
You can do a lot to prevent pinworms, however. Thorough hand washing is the best prevention. Other basic hygiene mea¬sures, such as daily bathing and wearing clean underwear, will help minimize pinworm infections.
When does my doctor need to be involved?
Call your doctor if the itching intensifies despite treatment. If your child has scratched so much that you think the skin is broken, you should contact your doctor.
What tests need to be done, and what do the results mean?
The only test used to confirm the presence of pinworms is a very simple one called the “Scotch tape test.” Both parents and doctors can perform this test. With your child on his hands and knees, press the sticky side of a piece of clear Scotch tape against the anus. Sometimes it helps to use a tongue depressor to gently press the tape to the skin. When the tape is removed seconds later, eggs and worms will stick to it. They should be easily visible.
What are the treatments?
Mebendazole (Vermox) is the most common treatment for pin¬worms. This antiparasitic is given one time, then typically repeated one to two weeks later. It is available as a single-dose chewable tablet, making it easy to give toddlers.
What are the possible complications?
Pinworm eggs may cohabitate with an intestinal infection called Dientamoeba fragilis. Infection with D.fragilis can cause chronic gastrointestinal upset and in some cases diarrhea.