Pinworms, an Easily Treated but Persistent Infection
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One of the prices of having children is pinworm (Enterobius vermiculari), a small white intestinal parasite that makes the human cecum and appendix its home.
The pinworm is generally innocuous, though insidious and persistent. During the night, while an infected person sleeps, a female pinworm creeps from the anus and deposits eggs on the surrounding skin, perhaps 10,000 of them. Then she dies.
Pinworms mature quickly, over approximately six hours, and by the time a person awakes the worms are infective. Pinworm can race through a household, and every member should be treated.
Pinworm infection, enterobiasis, is the most common nematode parasitic infestation of humans in the United States, said Joseph Bocchini, M.D., chief of pediatric infectious diseases at Louisiana State University in Shreveport, La. According to the CDC, up to 50% of all children have been infected at some point in their lives. Schools and daycare centers can be hotbeds for infection.
There is no thought of even trying to eradicate it from society. So we live with it. Julia McMillan, M.D., a professor of pediatrics at Johns Hopkins here, likens pinworm’s persistence to a common cold that drags on and on.
Why some children may be more susceptible to pinworm infection than others is unclear. Dr. McMillian says it’s more likely that behavioral factors are putting certain children at greater risk than others, not genetic susceptibility.
“As long as there are people around who are infected,” Dr. McMillan says, “they can spread the infection to other people.”
Pinworms are about the length of a staple—5 mm to 10 mm—and thrive in the human cecum and appendix. The eggs are usually ingested, infect the intestinal tract, and then the female pinworms leave the intestine through the anus where they deposit more eggs on the surrounding skin.
The eggs can infect within a few hours after landing on the skin. The eggs begin to lose infectivity after one to two days under warm and dry environmental conditions but may survive more than two weeks in cooler, more humid environments on clothes, particularly underwear and bedding.
Dr. McMillan is a member of the infectious disease committee at the American Academy of Pediatrics. She says young children with curious fingers are at the greatest risk of infection. They are the ones who are most likely to eat dirt or not wash their hands after using the bathroom. Or they touch a contaminated surface and then put their fingers in their mouths.
And then it can spread throughout the household. “As long as people are infecting they can transmit the infection through eating dirt and direct contact,” she says. “It’s like having bacteria on the surface of your skin. We can’t prevent that from happening and occasionally it results in infection.”
Ingestion is the most common route of infection, however, a study in the October issue of International Journal of Dermatology suggests infection may also occur, primarily among children, from inadequate hand washing, inhalation, or ingestion of airborne pinworm eggs.
The most obvious symptom is anal itching, which can be worse at night and disturb sleep, caused by the pinworm’s nocturnal peregrinations. Severe symptoms can include loss of appetite, restlessness and sleeplessness. Children can also become irritable.
However, pinworm infection doesn’t always cause symptoms. So many children and adults who become infected are asymptomatic and may be unknowingly spreading the infection, Dr. McMillan said.
There are two tests parents can use to determine whether their child is infected, according to the CDC. The first is a homespun technique called the Scotch tape test where parents apply the adhesive side of the tape to the anal area. The eggs become glued to the sticky tape and can be identified under a microscope.
The second test is called the pinworm paddle test and is available at doctors’ offices. It is the same as the Scotch tape test except it uses a plastic adhesive paddle to collect egg samples.
There are three oral drugs that are primarily used to treat pinworm. Two prescription antiparasitic drugs, Mebendazole and Zentel (albendazole), both work by blocking glucose from the worm. They are both well tolerated with a cure rate of 95% to 100%. These drugs should be avoided during pregnancy. Another drug, Pyrantel Pamoate, works differently. It paralyzes the worm, which is then expelled from the body. It has a cure rate of only 90% and has a higher rate of side effects. For these reasons, it is used less frequently.
Patients take one capsule once and then they take a second capsule a week later to ensure the worms and eggs have been killed and to help prevent recurrences due to reinfection. The CDC said children can return to school or daycare while on the treatment.
If a pinworm infection recurs, the same course of treatment is repeated. There are also recommendations from the CDC that may help reduce the spread of infection.
- Bathe in the morning to reduce egg contamination.
- Change and wash the patient’s underwear everyday. Also frequent changing of sleepwear is recommended. This is especially important after each treatment.
- Pinworm eggs are sensitive to sunlight. Open blinds and curtains in the bedrooms.
- Wash bedding because the eggs can survive on cloth for up to two weeks.
- Enforce personal hygiene. Wash hands after using the toilet, changing a diaper, and before and after eating.
- Discourage children from nail biting and keep children’s fingernails trimmed because the eggs can survive on the skin. Also this discourages the child from scratching the anal area and helps reduce the spread of infection.
While bathing, personal hygiene, and keeping clothes and bedding clean can help minimize infection, keeping the house spotless won’t really make much of a difference. This has puzzled many parents who question how pinworm infection could thrive when they were keeping an immaculately clean house.
The eggs, said Dr. McMillian, do not live on all kinds of surfaces. “They can persist on things like underclothes, but they’re not likely to persist on a rug or a countertop. Pinworms require very close contact with the human body.”
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