Threadworm

• Threadworm/pinworm:

  • Enterobius vermicularis
  • Common parasitic worm that infests the human gut
  • Transmission occurs by the faecal-oral route
  • Once ingested, larvae emerge from the eggs and mature within 1-2 months into adults in the small intestine
  • The mature adult female worm migrates through the anus and lays thousands of eggs on the peri-anal skin causing itching
• Prevalence:

  • Most common parasitic worm infestation in the UK
  • Mainly found in children, household contacts of infected children, and institutionalised people
  • Children aged 4-11 are most frequently affected, more commonly males
• Complications:

  • Lack of sleep due to itching - daytime irritability
  • Enuresis
  • Weight loss, anorexia
  • Excoriation and secondary infection of the perianal skin
  • Disease due to migration of adult worm to ectopic sites - female GU tract (vaginitis, salpingitis), urethra (urethritis)
  • Enterobius vermicularis associated appendicitis - pinworms or their eggs can block the appendiceal lumen
  • Rare - colitis, abscess, and granuloma formation
• Clinical features:

  • Intense perianal itching, typically worse during the night
  • Some people may be asymptomatic and only become aware of infection when small white thread-like worms are seen on the perianal skin or in the stools
  • In females the genital area can also be involved - pruritus vulvae
  • Nocturnal itching may lead to disturbed sleep and irritability
  • Signs of secondary bacterial infection due to excoriation of the perianal area
• Take a history asking about:

  • Symptoms of threadworm infection such as perianal and/or vulval itching and restlessness or insomnia.
  • Appearance of threadworms in the stools or on the peri-anal skin.
  • Contacts with similar symptoms or confirmed infection.
• Examine the person looking for:

  • Signs of scratching (excoriation) and localized secondary bacterial infection in the perianal area.
  • Worms in the perianal area (it is unusual to see these when the person is examined during the day).
• Investigations:

  • Can be diagnosed clinically
  • if diagnosis is uncertain - adhesive tape test for eggs
  • Apply transparent adhesive tape to perianal skin first thing in the morning before wiping/bathing
  • Tape is examined under microscope
• No exclusion from school is required
• Management:

  • Single dose on anthelmintic - mebendazole
  • Consider treated all household contacts
  • Advice rigorous hygiene measures for 2 weeks if treated with mebendazole, or 6 weeks if using hygiene measures alone
  • Hygiene measures alone - children under 6 months and pregnant women
• Hygiene measures:

  • Wash hands thoroughly with soap and warm water after using the toilet, changing nappies, and before handling food.
  • Cut fingernails regularly, avoid biting nails and scratching around the anus.
  • Shower each morning, including the perianal area, to remove eggs from the skin.
  • Change bed linen and nightwear daily for several days after treatment.
  • Do not shake out items as this may distribute eggs around the room.
  • Washing/drying in a hot cycle will kill threadworm eggs.
  • Thoroughly dust and vacuum (including vacuuming mattresses) and clean the bathroom by 'damp-dusting' surfaces, washing the cloth frequently in hot water.