The third larval stadium (元) represents the infective form of the parasite.įig. Larvae mature during their migration to the large intestine. Ingested eggs hatch in the small intestine (duodenum). vermicularis life cycle takes place in the gastrointestinal lumen. vermicularis are indeed infective as soon as they are expelled from female worms.Į. Differently from other helminth, eggs of E. The outer layer facilitates the adhesion of the eggs to the perianal region where they develop in infective larvae in about 4–6 h following oviposition and can survive for 2 or 3 weeks in the domestic environment, mainly on clothing, bedding and other objects or surfaces. Migration and egg hatching causes pruritus.Įggs 50–54 × 20–27 μm in size, are translucent, with an asymmetric shape and their shell is constituted by two parts. Gravid adult females migrate to the anal area mostly during the night and deposit thousands of eggs on perianal area. At maturity, adult females measure 9–12 mm and have a pointed tail, whereas males are 2–5 mm in length. vermicularis worms are tiny, thread-like and whitish. Pinto, Fabrizio Bruschi, in Encyclopedia of Infection and Immunity, 2022 Biology - Characteristics of the organismĮ. Careful laundering of all bedclothes is recommended as well.ī. All household contacts should be empirically treated with the same regimen to avoid reintroducing infection from family members who may be asymptomatically carrying the parasite. vermicularis is susceptible to standard albendazole 1 or mebendazole (see Table 2), pyrantel pamoate is most frequently used in the United States as it is cheap and effective.

It is also sometimes possible to see the small white female worms directly on the perianal region, although they are so small (8 to 13 mm in length) that they may easily be mistaken for residual bits of toilet paper. Eggs are small (25 × 50 μm) with a characteristic “bean-shaped” appearance. Sensitivity can be increased by examining at least three specimens. The tape can then be brought into a physician’s office or laboratory, where it is placed sticky side down for microscopic examination to detect the eggs. Pinworm infestation is best diagnosed by the classic Scotch tape test, which involves placing and immediately removing a piece of sticky tape firmly across the perianal area early in the morning when the eggs have been deposited.

Rarely, worms migrate into ectopic foci and produce painful genitourinary tract disease with granulomatous inflammation pinworm infection rarely results in pain that mimics acute appendicitis. Infection is often asymptomatic, but it can cause perianal itching, which helps to facilitate persistent infection by encouraging frequent touching of the perianal area. It can also be prevalent amongst institutionalized persons. In family groups, infection is associated with close living quarters, poor hand washing, and infrequent washing of clothes and sheets. Embryonated eggs can also attach to bedclothes, thereby placing other household members with close contact at risk for infection. In scratching the perianal area and subsequently bringing his or her hand to the mouth, the host ingests the embryos, which then hatch in the bowel about 2 months later and continue the cycle of infection. Within 6 hours, the eggs embryonate within their capsule and are infectious. At night, female worms travel to the anus and lay small (25 to 50 μm), double-walled oval eggs in the perianal skin. vermicularis is at maximum 1 cm long with a tapered tail, and dwells in the cecum, appendix, and adjacent colon. Its persistence is likely related to the fact that pinworm does not require a period of maturation outside the human body, and autoinfection or transmission by very close contact sustains the parasite within communities. It is the most common helminthic infection in the United States and Europe. vermicularis, is found throughout the world and continues to be diagnosed commonly in the United States, especially in children aged 5 to 10 years. Human pinworm infection, caused by the thread-like nematode E. Kellerman MD, in Conn's Current Therapy 2021, 2021 Enterobius vermicularis

Pin worms in humans