Infectious Disease · Parasitic Infections
The facts most likely to be tested
Enterobiasis is caused by the nematode Enterobius vermicularis, which is most commonly transmitted via the fecal-oral route through the ingestion of embryonated eggs.
The hallmark clinical presentation is nocturnal perianal pruritus caused by the female worm migrating to the perianal folds to deposit eggs at night.
The diagnostic gold standard is the Scotch tape test (or cellulose acetate tape test), performed in the early morning to capture eggs from the perianal skin.
Microscopic examination of the tape will reveal characteristic oval-shaped eggs that are flattened on one side.
First-line pharmacologic treatment for enterobiasis is albendazole or mebendazole.
Successful eradication requires treating the entire household simultaneously to prevent autoinfection and reinfection due to the high rate of transmission.
Pyrantel pamoate is an acceptable alternative treatment, particularly for patients who cannot tolerate or access benzimidazoles.
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A 6-year-old boy is brought to the clinic by his mother due to a 2-week history of intense perianal itching that is significantly worse at night. The mother reports that the child has been having difficulty sleeping and appears irritable during the day. Physical examination reveals excoriations in the perianal region, but no other skin lesions are noted. The child attends a local daycare center where several other children have reported similar symptoms. A Scotch tape test performed the following morning reveals oval-shaped eggs under microscopy.
What is the most appropriate management for this patient and his family?
Albendazole for the patient and all household members
The patient presents with classic nocturnal pruritus and a positive Scotch tape test diagnostic of Enterobiasis; treatment requires anthelmintic therapy for the patient and all household contacts to prevent reinfection.
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Etiology / Epidemiology
Caused by Enterobius vermicularis; most common helminthic infection in school-aged children via fecal-oral transmission.
Clinical Manifestations
Nocturnal perianal pruritus is the hallmark symptom due to female worm migration.
Diagnosis
Tape test (or Scotch tape test) performed in the early morning to identify eggs.
Treatment
Albendazole or Mebendazole; treat the entire household simultaneously.
Prognosis
Excellent prognosis; reinfection is common due to autoinoculation.
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Epidemiology & Etiology
Infection occurs via ingestion of eggs, often through contaminated fingers, bedding, or fomites. It is highly prevalent in daycare centers and crowded living conditions. The parasite Enterobius vermicularis is the sole causative agent.
Pertinent Anatomy
Adult worms reside in the cecum and ascending colon. Gravid females migrate through the anus to deposit eggs on the perianal skin, which triggers the characteristic inflammatory response.
Pathophysiology
Ingested eggs hatch in the small intestine and mature into adults. The female migrates to the perianal region at night to deposit thousands of eggs, causing intense pruritus ani. Scratching leads to egg transfer to fingernails, facilitating autoinoculation or transmission to others.
Clinical Manifestations
The classic presentation is nocturnal perianal pruritus that disrupts sleep. Patients may be asymptomatic, but severe cases can lead to excoriations from scratching. Secondary bacterial infection of the perianal skin is a potential complication. In females, ectopic migration can rarely cause vulvovaginitis.
Diagnosis
The tape test (Scotch tape test) is the diagnostic gold standard, performed by applying clear tape to the perianal skin upon waking. Microscopic examination reveals characteristic oval-shaped eggs with a flattened side. Stool ova and parasite exams are rarely diagnostic as eggs are deposited externally.
Treatment
Albendazole (400 mg) or Mebendazole (100 mg) is the first-line treatment. Teratogenic potential requires caution in pregnancy. Because of high reinfection rates, a repeat dose is mandatory after 2 weeks. All household members must be treated simultaneously to prevent the cycle of transmission.
Prognosis
Prognosis is excellent with high cure rates following appropriate anthelmintic therapy. Reinfection is the most common complication, often occurring within weeks. Hygiene measures, such as frequent handwashing and laundering of bed linens, are essential to prevent recurrence.
Differential Diagnosis
Atopic dermatitis: lacks nocturnal periodicity
Hemorrhoids: usually associated with bleeding or mass
Candida diaper dermatitis: presents with satellite lesions
Tinea cruris: presents with annular, scaly plaques
Anal fissures: associated with sharp pain during defecation