What are the causes, typical presentation, and recommended treatment—including medication regimen and hygiene measures—for Enterobius vermicularis infection in preschool- and school-aged children?

Pinworm Infection in Children: Causes, Presentation, and Treatment

Cause and Transmission

Pinworm infection is caused by the intestinal nematode Enterobius vermicularis, transmitted primarily through the fecal-oral route when microscopic eggs are ingested after contamination of hands, food, or airborne particles. 1, 2

• The parasite affects approximately 30% of children worldwide, with rates up to 60% in some developing countries 2
• Peak incidence occurs in children aged 3-6 years, particularly those aged 5-14 years 2, 3
• Predisposing factors include poor socioeconomic conditions, inadequate sanitation, overcrowding, and poor personal hygiene 2
• Adult female worms migrate to the perianal area at night to deposit eggs, which become infectious within hours 4, 2
• Eggs contaminate bedclothes, underwear, hands, and can become airborne, making the infection highly contagious 4
• Autoinfection occurs when children scratch the perianal area and transfer eggs to their mouth 4, 2

Clinical Presentation

The hallmark symptom is nocturnal perianal pruritus (anal itching), though 30-40% of infected children remain completely asymptomatic. 1, 5, 2

Key clinical features include:

• Intense anal itching, especially at night, causing restless sleep and irritability 1, 5, 4
• Visible white thread-like worms (6-13 mm) in the perianal area or stool 1, 2
• In females, vulvovaginitis from worm migration into the genital tract with possible vaginal discharge 1, 5, 6
• Less common symptoms: weight loss, abdominal pain, diarrhea, and occasionally colitis with eosinophilia 1, 5

Diagnosis

The "cellophane tape test" (adhesive tape test) performed on three consecutive mornings is the diagnostic standard, achieving approximately 90% sensitivity. 1, 5, 2

Diagnostic approach:

• Apply clear adhesive tape to the perianal region immediately upon waking, before bathing or defecation 1, 5, 4
• A single test has only 50% sensitivity; three tests on different mornings increase sensitivity to 90% 2
• Direct visualization of adult worms in the perianal area at night confirms diagnosis 1
• Stool examination is NOT recommended as eggs and worms are rarely present in feces 2
• Eosinophilia may be present in some cases, particularly with heavy infections 5

Treatment Regimen

First-line treatment is albendazole 400 mg as a single oral dose, repeated after 2 weeks to eliminate newly hatched worms. 1, 5, 2

Medication Options (all equally effective):

Albendazole:

• 400 mg single oral dose, repeat in 2 weeks 1, 5, 2
• Both adulticidal and ovicidal 2
• For children 12-24 months: requires expert consultation before use 1

Mebendazole:

• 100 mg single oral dose, repeat in 2 weeks 5, 2
• Both adulticidal and ovicidal 2
• FDA-approved and widely used 4

Pyrantel pamoate:

• 11 mg/kg (maximum 1 g) single dose, repeat in 2 weeks 2
• Only adulticidal (does not kill eggs) 2
• Preferred in pregnancy 2

Critical Treatment Considerations:

• The 2-week repeat dose is mandatory to kill worms that hatch from eggs surviving the initial treatment 1, 5, 2
• Treat all household members simultaneously, especially with multiple or recurrent symptomatic infections, as reinfection is extremely common 2
• Do NOT use during pregnancy (albendazole/mebendazole); pyrantel pamoate is preferred 4, 2

Hygiene Measures to Prevent Reinfection

Rigorous hygiene practices are essential as recurrence rates are high even with effective medication, primarily due to autoinfection and household transmission. 4, 2

Essential preventive measures:

Hand hygiene:

• Wash hands and scrub under fingernails with soap frequently, especially before eating and after using the toilet 4, 2
• Keep fingernails trimmed short 2
• Discourage nail-biting, finger-sucking, and scratching the anogenital area 2

Clothing and bedding:

• Wear tight-fitting underwear day and night, change daily 4
• Wash bed linens and nightclothes in hot water after treatment (do not shake to avoid dispersing eggs) 4
• Change underwear daily during treatment period 4

Environmental cleaning:

• Vacuum or damp-mop bedroom floors for several days after treatment 4
• Avoid dry sweeping that stirs up dust and aerosolizes eggs 4
• Keep toilet seats clean 4
• Bathe in the morning to remove eggs deposited overnight 2

Common Pitfalls to Avoid

• Never rely on stool examination alone for diagnosis—eggs are rarely present in stool 2
• Do not treat with a single dose only—the 2-week repeat is essential for cure 1, 5, 2
• Do not treat the index case alone—household transmission necessitates treating all family members 2
• Recognize that the vagina can serve as a reservoir for persistent infection in girls, causing recurrent episodes despite gastrointestinal treatment 6
• Understand that recurrence is usually reinfection (not treatment failure) due to the short 4-6 week life cycle and ease of transmission 2