Enterobius vermicularis (pinworm)

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Epidemiology

  • most common helminth infection among children in USA
  • primarily parasite among young children, but rapid maturation of egg allows transmission from child to child & child to adult within family & institutional setting
  • infection from ingestion of eggs on contaminated hands, food or water[5]

Pathology

  • male & female worms reside primarily in the cecum & adjacent areas
  • females grow to up to 13 mm in length & have a pointed posterior end, hence the common name pinworm
  • both sexes have prominent lateral alae (seen in cross-section) & a prominent esophageal bulb
  • gravid females migrate to the anus & deposit eggs in perianal folds[5]
  • females may be found on surface of stool specimen or on the perianal skin where the eggs are deposited, especially at night
  • hatched larvae migrate back into the anus & colon resulting in re-infection[5]
  • males are rarely seen
  • adult worms may migrate to ususual sites such as vagina, fallopian tubes & peritoneum
  • death of adult worms in ectopic sites may provoke an inflammatory granulomatous reaction
  • eggs are infective within 1 hour of deposition
  • complete development to gravid adult takes 1 month

Clinical manifestations

* image[4][5]

Laboratory

  • 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
  • eggs are colorless, ovoid with 1 side flattened
  • eggs measure 50-60 by 20-40 um
  • only 5-10% of cases identified during routine stool examination
  • diagnosis may take several samples taken on different days

* image[4][5][6]

Complications

Management

More general terms

Additional terms

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. 3.0 3.1 Prescriber's Letter 19(3): 2012 Alternatives to Vermox for Treatment of Intestinal Worms Detail-Document#: http://prescribersletter.com/(5bhgn1a4ni4cyp2tvybwfh55)/pl/ArticleDD.aspx?li=1&st=1&cs=&s=PRL&pt=3&fpt=25&dd=280308&pb=PRL (subscription needed) http://www.prescribersletter.com
  4. 4.0 4.1 4.2 Kang WH, Jee SC Enterobius vermicularis (Pinworm) Infection. N Engl J Med 2019; 381:e1. July 4, 2019 PMID: https://www.ncbi.nlm.nih.gov/pubmed/31269369 https://www.nejm.org/doi/full/10.1056/NEJMicm1811156
  5. 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 Grimm L What's Eating You: 12 Common Intestinal Parasites. Medscape. November 25, 2019 https://reference.medscape.com/slideshow/intestinal-parasites-6010996
  6. 6.0 6.1 Grim L You've Got Worms! Common Intestinal Parasites Medscape. Jan 23, 2023 https://reference.medscape.com/slideshow/intestinal-parasites-6014593