The intestinal nematode (roundworm) Enterobius vermicularis.
Egg transmission occurs by the fecal-oral route, either directly or indirectly via contaminated hands or objects such as clothes, toys, and bedding.
Pinworm is endemic worldwide and commonly clusters within families. Those most likely to be infected with pinworm are school-age children, people who take care of infected children, and people who are institutionalized. Travelers are at risk if staying in crowded conditions with infected people.
Incubation period is usually 1–2 months, but successive reinfections may be needed before symptoms appear. The most common symptom is an itchy anal region, which can disturb sleep. Adult worms can migrate from the anal area to other sites, including the vulva, vagina, and urethra. Secondary bacterial infection can occur from skin irritation.
The first option is to look for adult worms near the anus 2–3 hours after the infected person is asleep. The second option is microscopic identification of worm eggs collected by touching transparent tape to the anal area when the person first awakens in the morning. This method should be conducted on 3 consecutive mornings and before washing. The third option is microscopic examination of samples taken from under fingernails; samples should be taken before handwashing. Examining stool samples is not recommended because pinworm eggs are sparse.
Drugs of choice are mebendazole, albendazole, or pyrantel pamoate (which is available without prescription). Mebendazole is available in the United States only through compounding pharmacies. Each is given as a single dose and repeated in 2 weeks. In households where >1 member is infected or where repeated, symptomatic infections occur, all household members should be treated at the same time. For children younger than 2 years of age, in whom experience with these drugs is limited, risks and benefits should be considered by a physician before drug administration. Infected people should also bathe in the morning and change underwear and bedclothes frequently. Infected people should also practice personal hygiene measures such as washing hands before eating or preparing food, keeping fingernails short, not scratching the perianal region, and not biting nails.
Hand hygiene is the most effective method of prevention. Bed linen and underclothing of infected children should be changed first thing in the morning. They should not be shaken (to avoid contaminating the environment), and should be laundered promptly in hot water and followed by a hot dryer to kill any eggs that may be there.
American Academy of Pediatrics. Pinworm infection (Enterobius vermicularis). In: Kimberlin DW, editor. Red Book: 2015 Report of the Committee on Infectious Diseases. 30h ed. Elk Grove Village, IL: American Academy of Pediatrics; 2015. pp. 621–2.
American Public Health Association. Enterobiasis. In: Heyman DL, editor. Control of Communicable Diseases Manual. 19th ed. Washington, DC: American Public Health Association; 2008. pp. 223–5.
Kucik CJ, Martin GL, Sortor BV. Common intestinal parasites. Am Fam Physician. 2004 Mar 1;69(5):1161–8.