Threadworms

Definition
Threadworms are small, thin, white intestinal worms (Enterobius vermicularis) that commonly infect humans, particularly children. They live in the colon and rectum, and females lay eggs around the anus, causing intense itching.

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Cause & Transmission

• Caused by ingestion of E. vermicularis eggs from contaminated hands, food, or surfaces

• Spread by the faeco-oral route

• Autoinfection is common (scratching the anal area transfers eggs to fingers and under nails, then to the mouth)

• Eggs can survive for up to 2 weeks on surfaces, bedding, and clothing

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Risk Factors

• School-aged children

• Close living conditions

• Poor hand hygiene

• Nail biting or thumb sucking

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Life Cycle

• Eggs ingested → larvae hatch in small intestine → migrate to colon → female worms move to perianal area at night to lay eggs → itching leads to scratching and further spread

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Clinical Features

• Intense perianal itching (especially at night)

• Disturbed sleep, irritability

• Abdominal discomfort

• In females: vulval irritation or vaginal discharge (worms may migrate to genital tract)

• Sometimes asymptomatic

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Diagnosis

• Cellophane tape test: transparent adhesive tape pressed on the perianal area in the morning before washing, then examined microscopically for eggs

• Direct visualisation of worms in perianal region or stools

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Treatment

General hygiene measures (to prevent reinfection; essential alongside drug treatment)

• Wash hands before eating and after using toilet

• Keep nails short and clean; discourage nail biting

• Daily morning bathing to remove eggs

• Frequent washing of bedding, clothing, and towels in hot water

• Treat all household members simultaneously

Anthelmintic therapy (adults and children ≥2 years; repeat after 2 weeks to kill newly hatched worms)

• Mebendazole: 100 mg orally as a single dose; repeat in 2 weeks

• Albendazole: 400 mg orally as a single dose; repeat in 2 weeks

• Pyrantel pamoate (alternative):

  • Adults and children ≥2 years: 11 mg/kg orally (max 1 g) single dose; repeat in 2 weeks

• In pregnancy: drug treatment often deferred until after delivery unless symptoms are severe; hygiene measures prioritised

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Complications

• Sleep disturbance, fatigue

• Secondary bacterial infection from scratching

• Rarely: appendicitis, urinary tract infection, vulvovaginitis

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Quick-Reference Clinical Chart — Threadworms

Feature	Details
Organism	Enterobius vermicularis
Transmission	Faeco-oral; ingestion of eggs from contaminated hands/surfaces
Main symptoms	Night-time anal itching, disturbed sleep, irritability
Diagnosis	Cellophane tape test, visualisation of worms
First-line treatment	Mebendazole 100 mg PO single dose, repeat in 2 weeks
Alternatives	Albendazole 400 mg PO single dose, repeat in 2 weeks; pyrantel pamoate 11 mg/kg (max 1 g) single dose, repeat in 2 weeks
Hygiene measures	Handwashing, nail trimming, daily bathing, hot wash bedding/clothes
Household treatment	All members treated simultaneously to prevent reinfection