Hookworm

Aka: Hookworm, Necator americanus, Ancylostoma duodenale, N. americanus, New World Hookworm, A. duodenale, Old World Hookworm

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II. Epidemiology

  1. Second to Pinworm as most common US Helminth infection
  2. Found in areas of poor sanitation and severe poverty
  3. Widespread endemic areas
    1. Asia (China, India, Japan)
    2. Mideast
    3. Africa
    4. Southern Europe
    5. Caribbean
    6. Central America
    7. South America

III. Pathophysiology

  1. Human Hookworm: Blood sucking Nematode
  2. Size of both species
    1. Length: 10-12 mm females, 6-8 mm males
    2. Eggs: 60-70 um
  3. Infection
    1. Skin contacts larvae, typically in contaminated soil
    2. Bare feet are a common entry point (may also enter via hands, buttocks, legs)
    3. Skin penetration may be associated with intense localized itch ("ground itch)
  4. Life cycle
    1. Eggs hatch into rhabditform larvae
    2. Ingest soil Bacteria
    3. Molt into filariform larvae
    4. Larvae infect humans via pores, Hair Follicles, skin
    5. Larvae mature in blood
    6. Invade via alveolar capillaries into lung
    7. Ascend Bronchial tree via cough to be swallowed
    8. Mature worm attaches to Small Intestine wall
    9. Worm feeds and lays eggs in Small Intestine
    10. Eggs are then passed in stool to return to the soil and infect another person
  5. Species
    1. Necator americanus (New World Hookworm)
      1. Predominates in Americas and Carribean
      2. Mouth with both dorsal and ventral cutting plates
    2. Ancylostoma duodenale (Old World Hookworm)
      1. Predominates in Asia, Africa and Europe
      2. Mouth with 2 pairs of cutting teeth

IV. Symptoms

  1. Initial (usually asymptomatic)
    1. Pruritic erythematous dermatitis
    2. Mild respiratory symptoms
  2. Later: Gastrointestinal (onset 6 weeks after infection)
    1. Symptoms related to Anemia (see below)

V. Complications

  1. Anemia due to blood loss
    1. Hookworm ingests 0.25 ml of blood per day
  2. Results of Anemia in Children
    1. Malnutrition
    2. Failure to Thrive
    3. Mental Retardation

VI. Labs

  1. Microscopy for Ova and Parasites exam
    1. Examine stool at room Temperature
    2. Rhabditiform Larvae hatch
      1. Contrast with Strongyloides
  2. Complete Blood Count
    1. Hypochromic Microcytic Anemia
    2. Eosinophilia

VII. Management

  1. Treat concurrent Iron Deficiency Anemia
  2. Eradication of Helminth infection
    1. Mebendazole 100 mg PO bid for 3 days (not available as of 2012)
    2. Albendazole 400 mg PO for one dose
    3. Pyrantel Pamoate 11 mg/kg up to 1 gram for one dose

VIII. Prevention

  1. Always wear shoes in endemic areas
  2. Ensure adequate sanitation system

IX. References

  1. Kucik (2004) Am Fam Physician 69(5):1161-8 [PubMed]
  2. Schonau (2024) Am Fam Physician 109(6): 569-70 [PubMed]

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