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Enterobius vermicularis - Coggle Diagram
Enterobius vermicularis
Morphology
The adult female has a sharply pointed posterior end-8 to 13mm long, 0.5mm thick.
The adult male-2 to 5 mm long and 0.2 mm thick, and has a curved posterior end.
The eggs are translucent and have a surface that adheres to objects. The eggs measure 50 to 60 μm by 20 to 30 μm, and have a thick shell flattened on one side.
Eggs may contain a developing embryo or a fully developed pinworm larva.The larvae grow to 140–150 μm in length.
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Life cycle
Infection occurs via self-inoculation (transferring eggs to the mouth with hands that have scratched the perianal area) or through exposure to eggs in the environment (e.g. contaminated surfaces, clothes, bed linens, etc.)
Following ingestion of infective eggs, the larvae hatch in the small intestine and the adults establish themselves in the colon, usually in the cecum
The time interval from ingestion of infective eggs to oviposition by the adult females is about one month. At full maturity adult females measure 8-13 mm, and adult males 2-5mm; the adult life span is about two months. Gravid females migrate nocturnally outside the anus and oviposit while crawling on the skin of the perianal area
The larvae contained inside the eggs develop (the eggs become infective) in 4 to 6 hours under optimal conditions
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Clinical manifestation
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The most typical symptom is perianal pruritus, 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, teeth grinding, enuresia, insomnia, anorexia, irritability, and abdominal pain, which can mimic appendicitis
Diagnosis
Microscopic identification of eggs collected in the perianal area is the method of choice for diagnosing enterobiasis
To improve sensitivity, collection should be done in the morning, before defecation and washing, by pressing transparent cellulose tape (“Scotch test”, cellulose tape slide test) on the perianal skin and then examining the tape placed on a microscope slide.
Alternatively, anal swabs or “Swube tubes” (a paddle coated with adhesive material) can also be used for collection.
Treatment
Albendazole: Given on an empty stomach, a 400-mg, one-time dose followed by a repeat dose in 2 weeks
Mebendazole: A 100-mg, one-time dose followed by a repeat dose in two weeks
Pyrantel Pamoate: Available over the counter in the United States; Dose of 11 mg/kg up to a maximum 1 gm given 2 weeks apart
Other medications that have been used to treat enterobiasis are ivermectin and piperazine, although the latter has lower efficacy and higher toxicity
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