• Infection by a small, white nematode (roundworm), typically Enterobius vermicularis
  • Pinworms may also be caused by Enterobius gregorii in Europe, Africa, and Asia.


  • Considered the most common helminthic infection of humans (the only known natural host) and the most common worm infection in the United States
  • Occurs predominantly in school-aged children (5 to 10 years) and less commonly in preschool children
  • Does occur in adults, usually in those caring for infected children. Some individuals may be predisposed to either heavy or light worm burdens.
  • Independent of socioeconomic status


  • U.S. infection rates: 5–15%
  • Among children, people caring for infected children, and people who are institutionalized, prevalence can reach 50%.
  • Occurs worldwide but is more prevalent in temperate climates

General Prevention

  • Decontaminate the environment by washing underclothes, bedclothes, bedsheets, and towels.
  • Maintain good hand hygiene, including hand washing and proper toileting.
  • Keep fingernails short and avoid nail biting.
  • Treat family members and close contacts.


  • E. vermicularis eggs are ingested and hatch in the human’s stomach and duodenum. Then the larvae migrate to the ileum and cecum. Adult worms copulate in the cecum.
  • The pregnant female pinworm migrates from the cecum to the anus ~5 weeks later and deposits eggs on the perianal skin (at which point the female pinworm usually dies). Thousands of eggs are laid, which may result in hundreds of worms.
  • Pruritus is caused by the perianal deposition of eggs and a mucosal mastocytosis response. Other GI symptoms, such as anorexia or abdominal pain, may occur because of the mucosal inflammatory response.
  • Granulomas may form if dead worms and eggs invoke an inflammatory response in ectopic locations such as the peritoneal cavity, vulva, cervix, uterus, and fallopian tubes.


  • Ingestion of organism via fecal–oral transmission
  • Can be spread directly, hand-to-mouth, or via fomites found on toys, bedding, clothing, toilet seats, and baths

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