Enterobiasis (Pinworms)

Key Features

• This worldwide infection is caused by Enterobius vermicularis

• Adult worms are about 5–10 mm long and live in the colon

• Females deposit eggs on the perianal area, primarily at night, which cause intense pruritus

• Scratching contaminates the fingers and allows transmission back to the host (autoinfection) or to contacts through fecal-oral spread

Clinical Findings

• Intense localized pruritus of the anus and vulva

• Adult worms

  • May migrate within the colon or up the urethra or vagina in girls

  • Can be found within the bowel wall, in the lumen of the appendix (usually an incidental finding by the pathologist), in the bladder, and even in the peritoneal cavity of girls

Diagnosis

• The usual diagnostic test consists of pressing a piece of transparent tape on the child's anus in the morning prior to bathing, then placing it on a drop of xylene on a slide

• Microscopic examination under low power usually demonstrates the ova

• Occasionally, eggs or adult worms are seen in fecal specimens

• Parents may also visualize adult worms in the perianal region, often at nighttime while the child is asleep.

Treatment

• Personal hygiene must be emphasized

  • Nails should be kept short and clean

  • Children should wear undergarments in bed to diminish contamination of fingers

  • Bedclothes should be laundered frequently

  • Infected persons should bathe in the morning, thereby removing a large proportion of eggs

• Pyrantel pamoate

  • Available without a prescription

  • Given as a single dose (11 mg/kg; maximum 1 g)

  • Safe and very effective.

• Albendazole (400 mg or 200 mg in children 1–2 years of age) in a single dose is also highly effective for all ages (though not approved by the US FDA)

• Treat all household members at the same time to prevent reinfections

• Because the drugs are not active against the eggs, therapy should be repeated after 2 weeks to kill the recently hatched adults