Pinworms

Basics

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

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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