Pinworms

Definition

Pinworms, Enterobius vermicularis, are small, white worms that can live in the intestines, are common in young children, and are easily treated.

Description

Adult pinworms live in the large intestines. Males and females are about 5 mm and 10 mm long, respectively, with the diameter of a strand of thread. After copulation, the males die. When the female is ready to lay eggs, she crawls out of the anus, and violently expels the eggs on the skin around the anus. Some of the eggs become airborne and land elsewhere, but the majority stay on the skin of the buttocks. A single female can produce more than 10,000 eggs. After laying her eggs, the female also dies. At body temperature, the eggs develop quickly and are infective in about six hours. When ingested by another person, the eggs hatch in the small intestine. Juvenile worms grow into adult, sexually mature worms in about a month. These tiny worms are quite complex in that they have mouths, throats, gastrointestinal tracts, and a nervous system. The males and females have a complex reproductive tract and reproduce sexually. There is evidence that a protozoan parasite (Dientamoeba fragilis ) is transmitted among humans in the eggs of pinworms. Thus, they may occur simultaneously.

Transmission

Pinworms are extremely contagious, and the eggs are infective within a few hours of being laid. They are usually spread from child to child by contaminated fingers. When children scratch their itchy bottoms, the tiny eggs get under their fingernails. As they move around the house or classroom, the eggs can be spread. Eggs can stay on a child's skin for several hours. They can survive for two weeks on clothes, bedding, and toys . Children who touch the contaminated materials and then place their fingers in their mouths have provided a route for the tiny eggs to enter their bodies. The eggs stay in the upper part of the intestine until they hatch, then move down the length of the intestine and out the anus to lay eggs, and the cycle continues. The entire life cycle lasts four to six weeks. Sometimes adults breathe in the eggs when the bed covers are shaken; however, this is very uncommon. Transmission easily occurs by children not washing their hands thoroughly and spreading the infection to others. It is for this reason that if one member of a family is infected with pinworms, the whole family is treated.

Demographics

The pinworm Enterobius vermicularis is one of the most common nematode parasitic infections of humans in North America and Europe. It is estimated that pinworms infect more than 400,000,000 people throughout the world or approximately 10 percent of humans. There are no differences in pinworm infections on the basis of race or socioeconomic class. Neither is pinworm infection an indication of poor hygiene. This is a very easily transmissible infection that is quite widespread in children. Since the majority of children experience no ill effects whatsoever, extreme measures to treat pinworms are not indicated.

Causes and symptoms

Pinworm infections can be asymptomatic or result in mild gastrointestinal upsets. A common symptom associated with pinworm infections is perianal (around the anus) itching . Scratching of the perianal skin to relieve the itching can lead to bacterial infections that result in more itching, etc. Eventually, this cycle produces a great deal of discomfort. Children who are infected with pinworms often show symptoms that include restlessness, irritability, and insomnia. In females, the adult pinworms can enter the vagina and cause additional irritation. Since the pinworm almost always stays in the gastrointestinal tract or vagina, there is usually no systemic illness. A few children do develop intense nighttime itching of the skin around the anus. Girls who develop vaginal pinworm may experience vaginal itching or a vaginal discharge.

When to call the doctor

If the child seems restless at night and complains of itching in the morning, parents should call their health-care provider to obtain a pinworm lab kit. The kit consists of a tongue depressor with a piece of clear tape on the end. To use the kit, a parent should press the end of the tongue depressor, with the tape on it, against the child's anal skin. The tape is then placed, sticky-side down on a glass slide. The health-care provider will be able to see the eggs with a microscope, and the parent may even see them around the anus during the tape test.

Diagnosis

Stool and blood tests are not helpful in diagnosing pinworms. Seeing a worm is what determines the diagnosis. The parent must check the child's skin with a flashlight during the night and the first thing in the morning and look for white, wiggling threads. Occasionally a wiggling worm may be seen on the surface of a stool. Since pinworms are so common, children with nighttime anal itching are often treated without any lab test. The classic diagnostic tool is to apply a piece of transparent tape to the skin near the anus first thing in the morning. The health-care provider can attach it to a glass slide and then examine it under a microscope for the presence of eggs. A pinworm lab kit can usually be supplied by a provider's office if necessary.

Treatment

Treatment is with a single dose of an anti-pinworm drug such as albendazole (Albenza) or mebendazole (Vermox). Vermox comes as a chewable tablet and most children, as well as adults, experience no side effects with the medication. Allergic reactions have been rarely reported, and very rare cases of convulsions have occurred. The medication kills the worms about 95 percent of the time, but it does not kill the eggs. Therefore, retreatment in two weeks is recommended. Girls with vaginal itching alone do not necessarily need treatment, since the problem will often disappear on its own. Many healthcare providers disagree as to whether to treat the whole family, while others believe it is essential to treat the entire household. It is possible that a girl may be an asymptomatic carrier, which results in numerous reinfections. If everyone is treated, however, this problem will be alleviated. If the child is over two years of age, Pin-X (pyrantel pamoate) is an over-the-counter alternative to Vermox that is available as a liquid.

Prognosis

Treatment is usually very successful if followed with the prevention guidelines to prevent reinfection and doing a retreatment within two weeks after the first.

Prevention

Pinworm infections and reinfections can be diminished by the following:

• Make certain children wash their hands before meals and after using the restroom.
• Keep children's fingernails trimmed.
• Discourage nail-biting and scratching the anal area.
• Have children change into a clean pair of underwear each day.
• Have children bathe in the morning to reduce egg contamination.
• Open bedroom blinds and curtains during the day as eggs are sensitive to sunlight.
• After each treatment, change night clothes, underwear, and bedding and wash them.

Parental concerns

Since pinworms are so common and usually occur in children age 12 and under, there is no reason for concern unless the infection keeps reoccurring. In that case, meticulous cleaning and treatment with retreatment needs to be enforced.

KEY TERMS

Systemic —Relating to an entire body system or the body in general.

Resources

ORGANIZATIONS

American Academy of Pediatrics. 141 Northwest Point Blvd., Elk Grove Village, IL 60007-1098. (847) 434-4000. Web site: <www.aap.org>.

WEB SITES

Center of Disease Control and Prevention. Fact Sheet: Pinworms [cited March 6, 2005]. Available online at: </www.cdc.gov/ncidod/dpd/parasites/pinworm/factsht_pinworm.htm>.

iVillage. Pinworms: Why do they keep coming back? [cited March 6, 2005]. Available online at: <www.parentsplace.com/toddlers/health/qas/0,,239278_101260,00.html>.

Ohio State University. Pinworms. [cited March 6, 2005]. Available online at: <www.biosci.ohio-state.edu/~parasite/enterobius.html>.

Linda K. Bennington, MSN, CNS