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Ancylostoma duodenale (hookworm)

Epidemiology: 1) 25% of the world population is infected with hookworm, either Ancylostoma duodenale or Necator americanus 2) eggs are deposited with feces in the soil where rhabditiform larvae hatch & develop in 1 week to infectious filariform larvae 3) prevalent in southern Europe, north Africa & northern Asia 4) distribution overlaps with Necator americanus in southeast Asia 5) older children & adults in rural areas using unsanitary farming methods are most commonly & heavily infested Pathology: 1) infectious filariform larvae penetrate the skin of their host & reach the lungs via the bloodstream 2) larvae invade the alveoli & are transported by host clearance mechanisms to the epiglottis where they arewallowed & gain access to the small intestine 3) they use buccal teeth to attach to the small bowel mucosa & suck blood (0.2 mL/day/adult hookworm) 4) penetration of the skin to the adult form takes 6-8 weeks 5) larvae if swallowed may also develop into adults 6) adult worms are about 1 cm long 7) adult females produce thousands of eggs daily which are passed into the feces 8) adults generally live 6-8 years; 1-3 years [3] * image of adult worm [4] Clinical manifestations: 1) most infected individuals are asymptomatic 2) iron deficiency anemia may result 3) larvae may produce a pruritic maculopapular rash "ground itch" at the site of skin penetration 4) larvae migrating through the lungs may produce a mild transient pneumonitis (less frequently than with Ascaris) 5) epigastric pain & diarrhea may accompany early intestinal phase Laboratory: 1) diagnosis is made by recovery of eggs in the feces 2) eggs measure 40 by 60 um & are oval in shape 3) rhabditiform larvae may be observed if eggs allowed to hatch after a delay in examination 4) complete blood count (CBC) a) microcytic, hypochromic anemia with chronic infection b) eosinophilia with migratory phase 5) serum albumin: hypoalbuminemia Management: 1) the major consequence of chronic hookworm infection is iron deficiency anemia 2) antihelmintic agents a) mebendazole b) pyrantel pamoate c) albendazole 3) ferrous gluconate 320 mg PO TID

Related

Loffler's syndrome (simple pulmonary eosinophilia)

General

Ancylostoma

Properties

KINGDOM: animal PHYLUM: helminth

References

  1. Clinical Diagnosis & Management by Laboratory Methods, 19th edition, J.B. Henry (ed), W.B. Saunders Co., Philadelphia, PA. 1996, pg 1285-86
  2. Harrison's Principles of Internal Medicine, 13th ed. Isselbacher et al (eds), McGraw-Hill Inc. NY, 1994, pg 917-18
  3. Grimm L What's Eating You: 12 Common Intestinal Parasites. Medscape. November 25, 2019 https://reference.medscape.com/slideshow/intestinal-parasites-6010996
  4. Grim L You've Got Worms! Common Intestinal Parasites Medscape. Jan 23, 2023 https://reference.medscape.com/slideshow/intestinal-parasites-6014593