Overview
Definition:
Pinworm infection, also known as enterobiasis, is a common human intestinal parasitic infection caused by the nematode Enterobius vermicularis
It is characterized by intense perianal itching, particularly at night.
Epidemiology:
Pinworms are the most common helminthic infection worldwide, affecting an estimated 1 billion people annually
They are highly prevalent in children aged 5-10 years and in institutional settings
Transmission occurs through the fecal-oral route, often via contaminated hands, fomites, or ingestion of eggs.
Clinical Significance:
While generally not a life-threatening infection, pinworm infestation can cause significant discomfort, sleep disturbances, and secondary bacterial infections from scratching
In pediatric populations, recurrent infections can impact quality of life and school attendance
Accurate diagnosis and effective treatment are crucial for eradication and preventing household spread.
Clinical Presentation
Symptoms:
Intense perianal pruritus, especially at night
Restlessness and disturbed sleep
Irritability in children
Occasional anal discomfort or itching during the day
Rarely, abdominal pain, nausea, or vomiting
In girls, vulvovaginitis or urinary tract infections may occur due to migration of worms.
Signs:
Perianal erythema and excoriations from scratching
Visible adult worms or ova on perianal skin, especially with visual inspection at night or using tape test
No systemic signs of infection are typically present.
Diagnostic Criteria:
Diagnosis is primarily clinical, supported by identification of adult worms or ova
Diagnostic methods include: Cellulose tape test (most sensitive)
Visual inspection of the perianal area
Perianal swabbing
Rarely, visualization in stool or during sigmoidoscopy.
Diagnostic Approach
History Taking:
Inquire about pruritus, particularly nocturnal
Ask about sleep disturbances, irritability, and school absenteeism
Determine if other family members or household contacts have symptoms
Note any recent travel or institutional exposure
Ask about hygiene practices.
Physical Examination:
Focus on the perianal region
Look for erythema, excoriations, and evidence of itching
Gentle separation of buttocks may reveal adult worms
Examination of female genitalia and urinary meatus if vulvovaginitis or UTI symptoms are present.
Investigations:
Cellulose tape test is the gold standard for diagnosis
Instruct patient/caregiver to press clear adhesive tape against the perianal skin first thing in the morning before bathing or defecating
Transfer tape to a glass slide and examine under a microscope for ova or adult worms
Multiple tests may be needed for definitive diagnosis
Stool ova and parasite examination is less sensitive for pinworms.
Differential Diagnosis:
Other causes of pruritus ani: Fungal infections (e.g., Candida)
Bacterial infections
Allergic reactions or contact dermatitis
Hemorrhoids
Balanitis
Scabies.
Management
Initial Management:
Prompt symptomatic relief and eradication of infection
Emphasis on breaking the transmission cycle.
Medical Management:
Pharmacological treatment is the cornerstone
Albendazole and Mebendazole are the drugs of choice
Single-dose treatment is often effective, but a repeat dose after 2 weeks is recommended to eradicate newly hatched larvae
**Albendazole dosing**: For patients >2 years or weighing >10 kg: 400 mg orally as a single dose
Repeat dose after 2 weeks
For patients <2 years or weighing <10 kg: 200 mg orally as a single dose
Repeat dose after 2 weeks
**Mebendazole dosing**: For patients >2 years: 100 mg orally as a single dose
Repeat dose after 2 weeks
For patients <2 years: 50 mg orally as a single dose
Repeat dose after 2 weeks
Pamoate formulations are available but less commonly used due to complex dosing and potential side effects.
Household Treatment:
All members of the household, including asymptomatic individuals, should be treated simultaneously to prevent reinfection and break the transmission cycle
Treat family members and close contacts with albendazole or mebendazole as per their age/weight guidelines.
Supportive Care:
Advise meticulous hygiene practices: frequent handwashing with soap and water, especially after defecation and before meals
Keep fingernails short and clean
Discourage nail-biting
Daily bathing, focusing on the perianal area, and wearing tight-fitting underwear can reduce scratching and spread
Wash bedding, towels, and clothing in hot water and dry in a hot dryer
Vacuum carpets and upholstery
Consider topical corticosteroid creams for severe perianal itching to reduce inflammation and excoriation.
Complications
Early Complications:
Secondary bacterial infection of the perianal skin due to scratching
Sleep deprivation and irritability in children.
Late Complications:
Rarely, intestinal obstruction can occur due to a very heavy worm burden, particularly in individuals with compromised gastrointestinal motility
Migration of worms into the appendix can mimic appendicitis
Migration to the female genital tract can cause vulvovaginitis and pruritus
Urinary tract infections in young children.
Prevention Strategies:
Reinforce good personal hygiene, especially handwashing
Regularly trim fingernails
Discourage anal-digital contact and nail-biting
Simultaneous treatment of all household members
Regular cleaning of living areas and laundry.
Prognosis
Factors Affecting Prognosis:
Adherence to treatment and hygiene measures is crucial
Reinfection can occur if hygiene is poor or if household members are not treated.
Outcomes:
With appropriate antiparasitic treatment and adherence to hygiene recommendations, the prognosis is excellent
Symptoms typically resolve within a few days of treatment
Complete eradication is achievable.
Follow Up:
No routine follow-up is usually required if symptoms resolve
Advise patients to return if symptoms persist or recur, suggesting potential reinfection or poor adherence to treatment/hygiene
Family education on prevention is key for long-term success.
Key Points
Exam Focus:
Albendazole 400 mg single dose (repeat in 2 weeks) for adults and children >10 kg
Mebendazole 100 mg single dose (repeat in 2 weeks) for adults and children >2 years
Treat the entire household simultaneously
Diagnosis via cellulose tape test.
Clinical Pearls:
Nocturnal pruritus is the cardinal symptom
Always consider treating the entire family, even if asymptomatic, to break the transmission cycle
Patient education on hygiene is as important as medication
Reinfection is common if hygiene is not reinforced
For girls with vulvovaginitis, rule out pinworms first.
Common Mistakes:
Treating only the symptomatic individual and not the entire household
Failure to repeat the dose after 2 weeks, leading to treatment failure
Relying solely on stool O&P for diagnosis, which has low sensitivity for pinworms
Not emphasizing meticulous hygiene measures to patients and caregivers.