The nematode (roundworm) Enterobius vermicularis (previously Oxyuris vermicularis) also
called human pinworm. (Adult females: 8 to 13 mm, adult male: 2 to 5 mm.) Humans are
practically the only hosts of E. vermicularis.
Eggs are deposited on perennial folds. Self-infection occurs by transferring infective eggs
to the mouth with hands that have scratched the perennial area. Person-to-person
transmission can also occur through handling of contaminated clothes or bed linens.
Enterobiasis may also be acquired through surfaces in the environment that are
contaminated with pinworm eggs (e.g., curtains, carpeting). Following ingestion of
infective eggs, the larvae hatch in the small intestine and the adults establish
themselves in the colon. The time interval from ingestion of infective eggs to oviposition
by the adult females is about one month. The life span of the adults is about two months.
Gravid females migrate nocturnally outside the anus and oviposit while crawling on the
skin of the perennial area. The larvae contained inside the eggs develop (the eggs become
infective) in 4 to 6 hours under optimal conditions.
Worldwide, with infections more frequent in school- or preschool- children and in crowded
conditions. The most common helminthic infection in the United States (an estimated 40
million persons infected).
Enterobiasis is frequently asymptomatic. The most typical symptom is
especially at night, which may lead to excoriations and bacterial superinfection.
Occasionally, invasion of the female genital tract with vulvovaginitis and pelvic or
peritoneal granulomas can occur. Other symptoms include anorexia, irritability, and