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Threadworms: Advice for Referrers

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Threadworm (Enterobius Vermicularis) is a parasitic infection that affects the human gut. It is the most common parasitic infection in the UK, usually affecting children under the age of 18 years. They appear as small, white, thread-like worms between 2.5-12mm long.

They are spread via the faecal-oral route when threadworm eggs are ingested. Threadworms lay their eggs around the anus and can then be ingested via transfer from hand to mouth after scratching or by touching contaminated objects such as toys, clothes, bedding. The eggs can survive for up to 2 weeks, so repeat infection is common.

Red flags

Red flags to look out for:

  • Loss of appetite
  • Weight loss
  • Bedwetting (consider other diagnoses e.g. Type 1 diabetes)
  • Skin infections around anus caused by scratching
Information to Include: History

Please include the following points from history in the referral letter:

  • Any symptoms or signs patient might have, specifically itch (particularly intense, nocturnal, perineal itching is common with threadworms) and if any recurrent abdominal pain
  • Any previous episodes of threadworm
  • Any sleep disturbance and irritability at night
  • Any symptoms of vulvovaginitis
  • The treatment they have already received
  • Which other members of household, if any, are displaying similar symptoms and if they have been treated
Information to Include: Examination

Please include the following points from the clinical examination in the referral letter:

  • Any signs of scratching and localized secondary bacterial infection in the perineal area
  • Any visible small white worms on the perineum or in the stool
Suggestions for management whilst waiting for outpatient appointment

Treatment consists of medication and good hygiene measures:

Medication:

Mebendazole 100mg (1 dose) for children over the age of 6 months. All household members including adults and asymptomatic individuals should be treated with one dose. A second dose may be required in 2 weeks if re-infection occurs. Mebendazole is not recommended under the age of 6 months or for pregnant women and these patients are encouraged to manage symptoms with good hygiene measures

Hygiene measures:

Threadworm eggs can survive for up to 2 weeks outside the body on underwear, bedding and other objects. Good hygiene measures will help to clear eggs from the body and home and therefore prevent re-infection. Such measures include:

  • Keep fingernails short, wash hands and scrub nails every morning.
  • Always wash hands before meals and before preparing food, after the toilet and after nappy changes
  • Change and wash underwear, nightwear and bed linen every day at a hot temperature (at least 40 degrees)
  • Wash soft toys regularly (at least 40 degrees)
  • Vacuum all household carpets
  • Damp-dust smooth surfaces with wet cloth, particularly in children’s play area
  • Clean bathroom surfaces with a strong chlorine-based disinfectant
  • Rinse toothbrushes before use
Things you should not do:
  • Do not share towels or clothing
  • Do not shake beddings to prevent eggs from landing on other surfaces
  • Do not bite/suck fingers
If re-infection occurs:
  • Other causes of symptoms should be considered
  • Consider re-treatment with 1 dose mebendazole if diagnosis uncertain
  • Consider treatment with 3 day course of mebendazole (100mg for 3 days)
  • Reinforce strict hygiene measures

If the above are still ineffective then consider referral to a paediatrician for further investigation or management. However, in most cases strict hygiene measures have not been adhered to.

Editorial Information

Last reviewed: 17 November 2022

Next review: 30 November 2025

Author(s): Dr Mariann Buari (GPST2, Paediatrics) & Dr Nike Osifodunrin (Consultant Paediatrician)