Enterobius (Pinworm)

Trevor A. Crowell, M.D.


  • Pinworms are intestinal nematodes (aka roundworms).
  • The disease is also known as enterobiasis or threadworm disease, caused by Enterobius vermicularis.
  • Epidemiology: worldwide, with 40 million cases per year. Infection is mostly seen in children.
    • Most common nematode infection in the U.S.
    • Increased prevalence with congestion, institutionalization, and poor sanitation
      • A larger family size is associated with increased risk.
  • The lifespan of a worm is 11-35 days, so the chronic disease is due to reinfection rather than persistent infection.
    • Eggs are deposited nocturnally in perianal/perineal regions.
    • Self-infection can occur by transferring eggs to the mouth after scratching the affected area.
    • Eggs are transferred under contaminated fingernails, in dust and through contaminated clothes or linens.
  • Life cycle: (Figure 1)
    • Eggs are deposited on perianal folds by gravid females and transferred to the mouth by contamination of hands, clothes or bed linens.
    • Ingested eggs hatch into larvae in the small intestine.
    • Larvae mature into adults in the colon, and gravid females migrate nocturnally outside the anus to lay eggs.
    • Each female worm can produce more than 10,000 eggs. Eggs remain viable for an average of 1-2 weeks. Infectivity decreases within 1 to 2 days in dry, warm environments.

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Last updated: May 11, 2023