Last edited 06/2021 and last reviewed 10/2022

Enterobius vermicularis, also referred to as pinworm, threadworm or seatworm, is the most common helminthic infection seen in the USA and Western Europe.

  • formerly known as Occiyur vermicularis or oxyurides, this small, white obligate nematode affects 1000 million individuals worldwide (2)
  • affects all people regardless of age, gender or social status
    • 30% of children are infected with the parasite with children between the ages 7 to 11-years most commonly affected
    • female to male infectivity is 3:1
    • commonly seen in temperate climates
    • increased infectivity is seen with overcrowding and poor sanitation (1)

The adult worms reside in the caecum with the female migrating to the anus when ready to lay eggs; this usually occurs at night when they cause pruritus ani.

The eggs are transmitted by the faeco-oral route.

key points re: management (3):

  • treat all household contacts at the same time
  • advise hygiene measures for 2 weeks (hand hygiene; pants at night; morning shower, including perianal area)
  • wash sleepwear, bed linen, and dust and vacuum.
  • child <6 months, add perianal wet wiping or washes 3 hourly
  • child >6 months then treatment with mebendazole
    • 100mg stat; if reinfection occurs, second dose may be needed after 2 weeks (check summary of product characteristics before prescribing)
  • child <6 months or pregnant (at least in first trimester) then only hygiene measures for 6 weeks; mebendazole contraindicated


  1. Powell G, Sarmah P, Sethi B, Ganesan R. Enterobius vermicularis infection of the ovary. BMJ Case Reports. 2013;2013:bcr2013201146
  2. Dunphy L, Clark Z, Raja MH. Enterobius vermicularis (pinworm) infestation in a child presenting with symptoms of acute appendicitis: a wriggly tale! BMJ Case Rep. 2017;2017. pii: bcr-2017-220473.
  3. Public Health England (June 2021). Managing common infections: guidance for primary care