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Enterobius vermicularis (pinworm)

Epidemiology: 1) most common helminth infection among children in USA 2) primarily parasite among young children, but rapid maturation of egg allows transmission from child to child & child to adult within family & institutional setting 3) infection from ingestion of eggs on contaminated hands, food or water [5] Pathology: 1) male & female worms reside primarily in the cecum & adjacent areas 2) females grow to up to 13 mm in length & have a pointed posterior end, hence the common name pinworm 3) both sexes have prominent lateral alae (seen in cross-section) & a prominent esophageal bulb 4) gravid females migrate to the anus & deposit eggs in perianal folds [5] 5) females may be found on surface of stool specimen or on the perianal skin where the eggs are deposited, especially at night 6) hatched larvae migrate back into the anus & colon resulting in re-infection [5] 7) males are rarely seen 8) adult worms may migrate to ususual sites such as vagina, fallopian tubes & peritoneum 9) death of adult worms in ectopic sites may provoke an inflammatory granulomatous reaction 10) eggs are infective within 1 hour of deposition 11) complete development to gravid adult takes 1 month Clinical manifestations: 1) infection may be asymptomatic 2) pruritus ani, irritability & loss of sleep may occur 3) enuresis may be presenting symptom * image [4,5] Laboratory: 1) scotch tape test: Enterobius vermicularis on perianal skin - diagnosis is made by recovery of eggs & less commonly adult female worms from the perianal skin using the scotch tape test after the child has gone to bed or 1st thing in the morning 2) eggs are colorless, ovoid with 1 side flattened 3) eggs measure 50-60 by 20-40 um 5) only 5-10% of cases identified during routine stool examination 6) diagnosis may take several samples taken on different days * image [4,5,6] Complications: - appendicitis - urinary tract infections - vaginitis [5] Management: 1) mebendazole discontinued, use albendazole [3] 2) pyrantel pamoate (Pin-X) is OTC 3) piperazine citrate 4) treat entire household [5] 5) clean all bedding & clothing [5]

Related

mebendazole (Vermox, Emverm) piperazine pyrantel (Antiminth) scotch tape test; pinworm prep; Enterobius vermicularis in tissue

General

Enterobius

Properties

KINGDOM: animal PHYLUM: helminth

References

  1. Clinical Diagnosis & Management by Laboratory Methods, 19th edition, J.B. Henry (ed), W.B. Saunders Co., Philadelphia, PA. 1996, pg 1283
  2. Harrison's Principles of Internal Medicine, 13th ed. Isselbacher et al (eds), McGraw-Hill Inc. NY, 1994, pg 917
  3. Prescriber's Letter 19(3): 2012 Alternatives to Vermox for Treatment of Intestinal Worms Detail-Document#: 280308 (subscription needed) http://www.prescribersletter.com
  4. Kang WH, Jee SC Enterobius vermicularis (Pinworm) Infection. N Engl J Med 2019; 381:e1. July 4, 2019 PMID: 31269369 https://www.nejm.org/doi/full/10.1056/NEJMicm1811156
  5. Grimm L What's Eating You: 12 Common Intestinal Parasites. Medscape. November 25, 2019 https://reference.medscape.com/slideshow/intestinal-parasites-6010996
  6. Grim L You've Got Worms! Common Intestinal Parasites Medscape. Jan 23, 2023 https://reference.medscape.com/slideshow/intestinal-parasites-6014593