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Threadworm Infestation

An infestation of thin worms that lay eggs around the anus, causing intense itching

  • More common in children
  • Poor sanitation and inadequate personal hygiene are risk factors
  • Gender and genetics are not significant factors

Threadworm infestation is caused by the roundworm Enterobius vermicularis and is the most common parasitic worm infestation affecting humans in the UK. Usually, infestation occurs by ingesting worm eggs in contaminated food, on fingers, or in house dust. If they are swallowed, the eggs develop into adult threadworms in the intestine. At night, female threadworms crawl out of the anus to lay eggs around the anal region, causing intense itching. Threadworm infestation mainly affects children.

Threadworm eggs

Threadworms infest the intestine and emerge from the anus at night to lay eggs in the anal region, causing itching. Larvae can be seen inside the magnified eggs above.

What are the symptoms?

In most cases, the symptoms of threadworm infestation include:

  • Intense itching in the anal region at night when the worms lay eggs.

  • Inflammation of the anus as a result of constant scratching.

  • In some cases, mild abdominal pain.

Sometimes, tiny, white threadworms can be seen wriggling in the faeces after a bowel movement. In rare cases, infestation causes appendicitis.

What might be done?

The diagnosis can be confirmed by identification of threadworm eggs in a swab taken from the anal region. Your doctor will probably prescribe an anthelmintic drug to kill the worms effectively and speed recovery. Usually, the entire household is treated. Reinfection is common because the eggs can be picked up under the fingernails when scratching and accidentally swallowed. The cycle of infestation then begins again. Underwear, nightwear, and bedlinen may also be contaminated.

Threadworm infestation is usually easy to control. The risk of reinfection is reduced by scrupulous attention to personal hygiene: washing hands after going to the toilet, avoiding scratching the anal area, and washing clothes and bedlinen regularly.

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

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