Pinworm (Enterobius vermicularis)

Pinworm infection is common worldwide, especially in preschool and school‑aged children and in crowded settings. Humans are the only host. Infections frequently cluster within households and classrooms.

How it spreads

• Fecal–oral transmission: eggs from the perianal region contaminate fingers, nails, bedding, clothing, toys, and surfaces, then reach the mouth.
• Indirect spread: eggs on dust or fomites can be ingested after hand‑to‑mouth contact; airborne dust may be inhaled and subsequently swallowed.
• Autoinfection is common; “retroinfection” (larvae migrating from perianal region back to rectum) may occur but is less common.

Symptoms and signs

• Nocturnal perianal/perineal itching (worse at night) causing disturbed sleep, irritability, bruxism; secondary excoriations and dermatitis.
• Abdominal discomfort, reduced appetite, nausea are possible.
• Vulvovaginitis with itching/discharge can occur from migration in girls; urinary symptoms are uncommon but reported.
• Many infections are asymptomatic.

Diagnosis

• Perianal “tape test” is preferred: press clear adhesive tape to perianal skin immediately after waking, before toileting or bathing; place onto a slide. Repeat on 3 separate mornings to increase yield. Stool O&P has low sensitivity for pinworm.
• Visualization: adult worms may be seen on perianal skin 1–3 hours after the child falls asleep or on underwear/bed linens.

Treatment (safe, effective, and repeat in 2 weeks)

Treat the index patient and all close household contacts simultaneously to prevent ping‑pong reinfection.

• Albendazole: 400 mg orally once; repeat in 2 weeks. Pediatric dosing per local guidance (commonly 400 mg for ≥2 years; consider 200 mg for 12–24 months if used).
• Mebendazole: 100 mg orally once; repeat in 2 weeks.
• Pyrantel pamoate: 11 mg/kg (base) once, max 1 g; repeat in 2 weeks (available OTC in some regions).

Notes and cautions
– Pregnancy: avoid albendazole/mebendazole in the first trimester when possible; pyrantel pamoate is often preferred—follow obstetric guidance.
– Breastfeeding: generally compatible; verify local recommendations.
– Ivermectin is not first‑line for pinworm. Avoid outdated or toxic topical agents (e.g., mercurials).

Household and hygiene measures (reduce reinfection)

• Hand hygiene: soap and water after toileting/diaper changes and before eating or food prep; keep fingernails short and discourage nail‑biting/thumb‑sucking.
• Morning bathing: shower each morning to remove overnight eggs; change underwear daily.
• Laundry and cleaning: wash underwear, pajamas, bed linens, and towels frequently in hot water; avoid shaking linens; vacuum and damp‑wipe surfaces.
• School/daycare: return is usually allowed once treatment is started; coordinate with local policies during outbreaks.

When to seek care

• Persistent symptoms despite two properly timed treatment doses and hygiene measures.
• Severe vulvovaginitis, secondary skin infection, weight loss, or significant sleep disturbance.
• Suspected medication adverse effects or pregnancy requiring individualized therapy.

Key points

• Diagnose with the morning tape test; stool tests are usually not helpful.
• Treat all household contacts and repeat the dose in 2 weeks.
• Combine medication with strict hygiene to prevent reinfection.

Educational information only; follow local clinical guidance for dosing in young children and during pregnancy.