What is pinworm?

So many of us or our family members have experienced this relatively mild though distressing infection. Pinworm is the most common worm infection in North America with up to 50% of some groups of school aged children getting infected. It is estimated that there are 500 million infections worldwide and 40 million at any one time in the U.S.

E. vermicularis image/CDC

Pinworm, or Enterobius vermicularis, is a small intestinal roundworm about the size of a staple. The female adult worms leave the anus in the middle of the night while the person is sleeping to deposit her eggs around the skin of the perianal region.

The eggs become infectious within a couple of hours after being deposited and can survive for about 2 weeks outside the host.

Many people may be asymptomatic. In others there may be rectal itching and eczema, disturbed sleep, irritability, and secondary bacterial infection of scratched skin. Rarely worms are known to migrate into other areas like the vagina in young girls. Pinworms should be suspected in young girls with persistent vulvovaginitis.

The mode of infection with pinworm is through transfer of infective eggs by hand to mouth, frequently after scratching the perianal region and indirectly through clothing, bedding, food and other articles contaminated with eggs. Eggs get dispersed around the house, especially in the bedroom.

Pinworm infection is most common in school aged children, followed by preschoolers and is lowest in adults except for mothers of infected children. Whole families can get infected with this worm.

This infection is easily diagnosed by applying scotch-tape or a pinworm paddle to the perianal area and examining this microscopically for characteristic eggs. Specimen should be collected early morning before bathing or the passage of stools. Eggs are rarely found in stool samples.

In children over age two years, treatment usually includes either mebendazole (Vermox) or Pin-X (pyrantel pamoate), an over-the-counter alternative to Vermox that is available as a liquid.

One of the keys to treatment of pinworms is to repeat the dose in 2 weeks to be sure and kill newly hatched eggs. Also, since some family members may have a pinworm infestation without symptoms, it is sometimes recommended that the whole family be treated, taking caution in treating children under age 2 years and pregnant women (ask your doctor first).

Reinfection with pinworm occurs rather easily. Strict observance of good hand hygiene is essential (e.g. proper handwashing, maintaining clean short fingernails, avoiding nail biting, avoiding scratcing the perianal area) to prevent reinfection.

Other preventive measures include:

• Daily morning bathing and changing of underclothes helps remove a large proportion of pinworm eggs and can help prevent infection and reinfection. Showering may be preferred to avoid possible contamination of bath water.
• Careful handling (avoid shaking) and frequent laundering of underclothes, night clothes, towels, and bed sheets using hot water also helps reduce the chance of infection and reinfection by reducing environmental contamination with eggs.
• Clean and vacuum house daily for several days after treatment.

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