Pinworms

Author: Daniel Jun Yi Wong, Medical Student, University of Melbourne, Australia, 2012.

What are pinworms?

Pinworms (Enterobius vermicularis) are small roundworms that live in the lower digestive tract of humans. They are also called threadworms, enterobiasis and oxyuriasis. Infestation or infection with pinworms is most common amongst school-aged children, in some communities affecting up to two-thirds of children aged 5-10 years.

What are the symptoms of pinworm infestation?

The most common symptom caused by pinworms is itching around the anus, also called pruritus ani. The itchiness tends to be worse at night and can cause trouble sleeping. The itching is caused by an inflammatory reaction to the adult worm and eggs on the skin.

The adult worms sometimes migrate to the vagina instead of returning to the bowel. This may result in a itchy vaginitis with a mucous or blood-stained discharge.

Scratching may lead to bacterial infection (impetigo) with crusting and oozing.

Severe infestations very rarely result in abdominal pain, nausea, or vomiting.

Why are pinworms so itchy at night?

At night, the female adult pinworm leaves the anus to deposit eggs onto the skin around the anus. After exposure to the air, the microscopic eggs mature and are typically infectious within a couple of hours. They can survive for up to 2 weeks outside the body.

How do pinworms spread?

The main way that pinworms spread is through swallowing the eggs. When someone with pinworm scratches their anus, the eggs get lodged beneath their fingernails, and are then deposited on clothing and furniture. Uninfested individuals can come in contact with pinworm eggs and ingest them unknowingly. Infested individuals continue to ingest the eggs (auto-infection).

Other family members are at particular risk of pinworm infestation.

How is pinworm infection confirmed?

The adult worms can sometimes be seen with the naked eye, as thin, white, wriggling threads about 1-2 cm in length. Look at the anus at night or at the surface of bowel motions.

A ‘sticky tape’ test involves sticking a piece of clear adhesive tape to the crease of the anus, and is best carried out at night. The tape should catch any pinworm eggs, which can confirmed by looking at the tape under the microscope.

How are pinworms treated?

It is important to prevent the spread of infection by maintaining good hygiene (hand washing with soap and water, keeping fingernails short, taking a shower or bath daily), washing linens and clothes, and trying not to scratch in order to prevent contact with the pinworm eggs.

Mild infections can clear by themselves. However, pinworm infection is usually treated with albendazole or mebendazole. A single dose has a relatively high cure rate. A second dose two weeks later helps to prevent recurrence of the infection. After each dose bed linen should be changed and the bedroom vacuumed.

Because re-infection is common, it is sensible to treat the whole family at the same time to prevent recurrence and spread of infection to others.

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