Hookworm

Key Features

Essentials of Diagnosis

• Iron-deficiency anemia

• Abdominal discomfort, weight loss

• Ova in the feces

General Considerations

• 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

Demographics

• 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

Clinical Findings

• 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

Diagnosis

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

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

Treatment

• 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

Outcome

Prevention

• Avoiding fecal contamination of soil

• Avoiding barefoot skin contact with potentially contaminated soil

Prognosis

• Excellent after therapy

• However, reinfection is common in endemic areas

References