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Key Features

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Essentials of Diagnosis
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  • Iron-deficiency anemia

  • Abdominal discomfort, weight loss

  • Ova in the feces

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General Considerations
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  • Common human hookworms are Ancylostoma duodenale and Necator americanus

  • The larger A duodenale is more pathogenic because it consumes more blood, up to 0.5 mL per worm per day

  • Larvae penetrate human skin on contact, enter the blood, reach the alveoli, are coughed up and swallowed, and develop into adults in the intestine

  • The adult worms attach to intestinal mucosa, from which they suck blood

  • Infection rates reach 90% in areas without sanitation

  • Ancylostoma braziliense and Ancylostoma caninum (the dog and cat hookworm)

    • Cause cutaneous larva migrans

    • Larvae can move up to a few centimeters a day and activity can continue for several weeks, but eventually the rash is self-limiting

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Demographics
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  • A duodenale and N americanus

    • Both are widespread in the tropics and subtropics

    • An estimated 600–700 million people infected worldwide

  • In the United States, the disease is most prevalent in the Southeast

  • Most cases in the United States are imported by travelers returning from tropical and subtropical areas

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Clinical Findings

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  • Patients are asymptomatic or have complaints of diarrhea

  • Chronic infection leads to blood loss and iron deficiency anemia

  • Heavy infection can cause hypoproteinemia with edema

  • Chronic infection in children may lead to

    • Growth delay

    • Deficits in cognition

    • Developmental delay

  • A stinging or burning sensation is experienced as larvae penetrate skin of feet, followed by an intense local itching (ground itch) and a papulovesicular rash that may persist for 1–2 weeks

  • Pneumonitis associated with migrating larvae is uncommon and usually mild, except during heavy infections

  • Colicky abdominal pain, nausea, diarrhea, and marked eosinophilia may be present

  • Larvae of A braziliense and A caninum produce

    • Pruritic, reddish papules at the site of skin entry

    • Intensely pruritic, serpiginous tracks or bullae, which is pathognomonic

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Diagnosis

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  • Large ova of both species are found in feces and are indistinguishable

  • Microcytic anemia, hypoalbuminemia, eosinophilia, and hematochezia occur in severe cases

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Treatment

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  • Albendazole (400 mg orally in a single dose, or 200 mg in children 1–2 years of age)

    • Drug of choice

    • Significantly more efficacious than mebendazole or pyrantel pamoate

  • Mebendazole (100 mg orally twice a day for 3 days) or pyrantel pamoate (11 mg/kg, to a maximum of 1 g, daily for 3 days) are second-line options

  • Iron therapy may be as important as worm eradication

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Outcome

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Prevention
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  • Avoiding fecal contamination of soil

  • Avoiding barefoot skin contact with potentially contaminated soil

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Prognosis
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  • Excellent after therapy

  • However, reinfection is common in endemic areas

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References

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Bethony  J  et al: Soil-transmitted helminth infections: ascariasis, trichuriasis, and hookworm. Lancet 2006;367:1521 ...

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