Definition, Etiology, PathogenesisTop
1. Etiologic agent: Nematode Enterobius vermicularis (pinworm), a 2 to 13 mm-long parasite of the large intestine. Infection occurs after ingesting the eggs. The larvae hatch in the duodenum and travel to the large intestine (cecum and ascending colon), where they mature. Subsequently fertilized female worms migrate to the anal area and deposit eggs on the skin. The eggs mature within 6 hours.
2. Reservoir and transmission: Humans are the only reservoir. Infection spreads easily via the fecal-oral route, predominantly through contaminated hands (direct contact with an affected person; indirectly through underwear, clothing, bed linens, or towels belonging to an affected individual or through contaminated toys, toilet seats, bathtubs) or contaminated food. Self-invasion is common (due to scratching of the anal area and hand-to-mouth transfer of eggs). Retroinvasion is also possible (the larvae hatch in the perianal area and get to the host’s gastrointestinal tract through the anus), as well as infection by inhalation.
3. Risk factors: Poor hygiene and sanitary conditions; employment in daycare centers, preschools, orphanages; enterobiasis in a household contact.
4. Incubation and contagious period: The eggs appear in stool 2 to 8 weeks from infection. The patient is contagious for the entire duration of egg shedding (eggs remain infective in cool and moist environments for 2-3 weeks and are resistant to chlorine).
The disease is prevalent worldwide and typically develops in children in preschool and early elementary grades.
Clinical Features And Natural HistoryTop
Most frequently the infection is asymptomatic. The leading symptom is perianal pruritus, which occurs particularly at night and often causes anxiety, crying in children, and sleep disturbances. Some patients may develop loss of appetite, irritability, and secondary bacterial perianal skin infection. In rare cases ectopic invasion of the female genital organs or urinary tract or chronic pelvic peritonitis may occur.
Diagnosis is based on identification of eggs in the perianal area through visual inspection with laboratory confirmation (microscopic examination of a specimen collected through an adhesive cellophane tape applied on the skin in the perianal region [cellophane tape test]). Adult female worms may be occasionally observed in the perianal area or on the surface of stool. Stool examination is not useful in the diagnostic workup of enterobiasis, as the eggs are not excreted with feces.
1. Daily household cleaning (removing dust) is recommended, as well as daily changing of underclothing, bed linens, and towels (these should be washed at high temperatures), cutting fingernails short, and taking a shower every morning (this removes the majority of eggs from the skin). Daily washing of the perianal area with soap and warm water is also an efficient measure of limiting self-invasion.
2. All household and other close contacts should be treated simultaneously.
3. Thorough household cleaning and change of underwear and bed linens on the day of treatment.
1. The first-line drug is oral pyrantel 10 mg/kg in a single dose (maximum 1 g). Treatment should be repeated after 2 weeks due to frequent reinvasions.
2. The second-line drug (the Centers for Disease Control and Prevention [CDC] recommend it at the same level as pyrantel) is oral mebendazole 100 mg or oral albendazole 400 mg in a single dose (irrespective of the patient’s age). Treatment should be repeated after 2 weeks.
3. Treatment in pregnancy: Only if the symptoms are troublesome (pyrantel is the preferred drug).
4. Treatment of reinvasion: As in primary invasion.
Washing hands with soap and warm water before preparing and consuming meals as well as after using the toilet, avoiding nail biting and scratching the perianal area, washing fruit and vegetables, avoiding consumption of foods from unknown sources.