The intestinal nematode (roundworm) Enterobius vermicularis.
Direct transfer of eggs by hand from anus to mouth, which can reinfect the same person or infect a different person, or indirect transmission via objects such as clothes and bedding that are contaminated with eggs.
Endemic worldwide. Travelers are at risk if staying in crowded conditions with infected people. Frequently transmitted within families.
Incubation period is usually 1–2 months, but successive reinfections may be needed before symptoms appear. The most common symptom is perianal itching, which can disturb sleep. Adult worms can migrate from the anal area to other sites, including the vulva, vagina, and urethra. Secondary bacterial infection of scratched skin can also occur.
Direct visualization of adult worms near the anus, best done 2–3 hours after the infected person has fallen asleep, or microscopic identification of worm eggs collected by touching transparent tape to the anal area when the person first awakens in the morning.
Drugs of choice are mebendazole, albendazole, and pyrantel pamoate (can be purchased without prescription). Treatment is repeated 2 weeks after the initial dose. In households where >1 member is infected or where repeated, symptomatic infections occur, all household members should be treated at the same time.
Handwashing; maintaining clean, short fingernails; avoiding nail biting; avoiding scratching the perianal or perineal region; daily morning bathing (showers or stand-up baths best): and frequent changing and laundering of underclothes, nightclothes, and bedding with hot water help prevent the spread of the infection and reinfection of the same person.
American Academy of Pediatrics. Pinworm infection (Enterobius vermicularis). In: Pickering LK, editor. Red Book: 2012 Report of the Committee on Infectious Diseases. 29th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2012. p. 566–7.
American Public Health Association. Enterobiasis. In: Heyman DL, editor. Control of Communicable Diseases Manual. 19th ed. Washington, DC: American Public Health Association; 2008. p. 223–5.
Kucik CJ, Martin GL, Sortor BV. Common intestinal parasites. Am Fam Physician. 2004 Mar 1;69(5):1161–8.