II. Epidemiology
- Most common in children ages 5 to 14 years
- Most common Helminth infection in the United States (Incidence as high as 40 million/year)
-
Prevalence: 209 million children infected worldwide
- Worldwide, 30% of children are infected
III. Pathophysiology
- Intestinal roundworm (nematode) infection
- Humans are only known host
- Life Cycle
- Enterobious eggs are ingested
- Larvae hatch in duodenum
- Worms live in ascending colon at cecum
- Female worms migrate to anus and perineum at night to deposit eggs
- May lay up to 15,000 eggs nightly
- Majority of eggs dry-out within 3 days
- However Pinworm eggs may have as much as a 20 day external viability
- Enterobious eggs are ingested
- Transmission
- Scratching of perianal or perineal Pruritus results in transmission of eggs to fingers
- Further transmission to other fomites (bedding, clothing)
- Ingestion of Pinworm ova
- Fecal-oral transmission of eggs
- Passed by direct contact or fomites (hands, clothing, house dust)
- Scratching of perianal or perineal Pruritus results in transmission of eggs to fingers
IV. Risk Factors
V. Symptoms
- Often asymptomatic
- Perianal or perineal Pruritus worse at night
- May also cause vaginal irritation
- Restlessness at night
VI. Signs
- See Pinworm Test (Cellophane Tape Test)
- Small (0.5 to 1 cm) white worms at perianal area
VII. Differential Diagnosis
- See Pruritus Ani
- See Pruritus Vulvae
VIII. Labs
- Pinworms are not found in the stool
-
Pinworm Test
- Best yield at night or early morning
IX. Course
- Self limited; resolves by 6 weeks (unless reingested)
X. Management
-
Pyrantel Pamoate (Pin-Rid, OTC)
- Dose: 11 mg/kg up to 1 gram PO for 1 dose (age 2 or older)
- Repeat dose in 2 weeks
- Avoid in pregnancy or age under 2 years old
- Available as over-the-counter medication, and only $20 per 2 dose course
- Cure rates >90%
-
Mebendazole (Vermox, Emverm)
- Dose: 100 mg chewable for 1 dose (age 2 or older)
- Repeat dose in 2 weeks (per CDC and despite package insert)
- Avoid in first trimester of pregnancy or age under 2 years old
- Was not available as of 2012, and available as of 2016 at $740/course
- Cure rates >90%
-
Albendazole (Valbazen, Albendazole)
- Age >=2 years: 400 mg orally for 1 dose
- Age <2 years: 200 mg orally for 1 dose
- Repeat dose in 2 to 3 weeks
- Avoid in first trimester of pregnancy (or age under 1 year old)
- As with Mebendazole, very expensive in U.S. (>$600/course)
XI. Management: Other measures
- Treat household contacts (esp. if 2 or more members affected)
- Reinfection is common
- Encourage Hand Washing and morning shower or bath
- Clean all linen, clothing in hot water (eggs survive 2-3 weeks on objects)
XII. Complications
- Secondary localized Bacterial Infections
- Due to Pruritus, scratching and localized inflammation
-
Appendicitis (rare)
- May complicate chronic Pinworm infections
XIII. Prevention
- Hand Hygiene is the most effective overall prevention measure
XIV. References
- Gilbert et al (2016) Sanford Guide to Antimicrobial Therapy, accessed IOS app 5/4/2016
- Kazura in Behrman (2000) Nelson Pediatrics, p. 1067-8
- (2016) Presc Lett 23(5): 28
- (2012) Presc Lett 19(3): 16
- Markell (1985) Pediatr Clin North Am 32(4):971-86 [PubMed]
- Pyzocha (2023) Am Fam Physician 108(5): 487-93 [PubMed]
- Schonoau (2024) Am Fam Physician 109(6): 569-70 [PubMed]