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