Helminth

Pinworm

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Pinworm, Enterobius vermicularis, Enterobiasis

  • Epidemiology
  1. Most common in children ages 5 to 14 years
  2. Most common Helminth infection in the United States
  3. Prevalence: 209 million children infected worldwide
    1. Worldwide, 30% of children are infected
  • Pathophysiology
  1. Intestinal roundworm (nematode) infection
    1. Humans are only known host
  2. Transmission
    1. Fecal-oral transmission of eggs
  3. Larvae hatch in duodenum
  4. Worms live in ascending colon at cecum
    1. Female worms migrate to perineum at night
    2. May lay up to 15,000 eggs nightly
  5. Majority of eggs dry-out within 3 days
  • Transmission
  1. Ingestion of Pinworm ova (20 day viability)
  2. Passed by fomites (hands, clothing, house dust)
  3. Female worms migrate to anus at night to deposit eggs
  • Symptoms
  1. Perianal or perineal Pruritus worse at night
  2. May also cause vaginal irritation
  3. Restlessness at night
  • Signs
  1. Small (0.5 to 1 cm) white worms at perianal area
  • Differential Diagnosis
  1. See Pruritus Ani
  2. See Pruritus Vulvae
  • Labs
  1. Pinworm Test
  • Course
  1. Self limited; resolves by 6 weeks (unless reingested)
  • Management
  1. Pyrantel pamoate (Pin-Rid, OTC)
    1. Dose: 11 mg/kg up to 1 gram PO for 1 dose
    2. Repeat dose in 2 weeks
    3. Avoid in pregnancy or age under 2 years old
    4. Available as over-the-counter medication, and only $20 per 2 dose course
  2. Mebendazole (Vermox, Emverm)
    1. Dose: 100 mg chewable for 1 dose
    2. Repeat dose in 2 weeks (per CDC and despite package insert)
    3. Avoid in first trimester of pregnancy or age under 1 year old
    4. Was not available as of 2012, and available as of 2016 at $740/course
  3. Albendazole (Valbazen, Albendazole)
    1. Dose: 400 mg PO for 1 dose
    2. Repeat dose in 2 weeks (age 2 or older)
    3. Avoid in first trimester of pregnancy or age under 1 year old
    4. As with Mebendazole, very expensive in U.S. (>$600/course)
  • Management
  • Other measures
  1. Treat household contacts (esp. if 2 or more members affected)
  2. Encourage Hand Washing and morning shower or bath
  3. Clean all linen, clothing in hot water (eggs survive 2-3 weeks on objects)
  • References
  1. Gilbert et al (2016) Sanford Guide to Antimicrobial Therapy, accessed IOS app 5/4/2016
  2. Kazura in Behrman (2000) Nelson Pediatrics, p. 1067-8
  3. (2016) Presc Lett 23(5): 28
  4. (2012) Presc Lett 19(3): 16
  5. Markell (1985) Pediatr Clin North Am 32(4):971-86 [PubMed]