Ancylostoma duodenale (hookworm)
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Epidemiology
- 25% of the world population is infected with hookworm, either Ancylostoma duodenale or Necator americanus
- eggs are deposited with feces in the soil where rhabditiform larvae hatch & develop in 1 week to infectious filariform larvae
- prevalent in southern Europe, north Africa & northern Asia
- distribution overlaps with Necator americanus in southeast Asia
- older children & adults in rural areas using unsanitary farming methods are most commonly & heavily infested
Pathology
- infectious filariform larvae penetrate the skin of their host & reach the lungs via the bloodstream
- larvae invade the alveoli & are transported by host clearance mechanisms to the epiglottis where they arewallowed & gain access to the small intestine
- they use buccal teeth to attach to the small bowel mucosa & suck blood (0.2 mL/day/adult hookworm)
- penetration of the skin to the adult form takes 6-8 weeks
- larvae if swallowed may also develop into adults
- adult worms are about 1 cm long
- adult females produce thousands of eggs daily which are passed into the feces
- adults generally live 6-8 years; 1-3 years[3]
* image of adult worm[4]
Clinical manifestations
- most infected individuals are asymptomatic
- iron deficiency anemia may result
- larvae may produce a pruritic maculopapular rash "ground itch" at the site of skin penetration
- larvae migrating through the lungs may produce a mild transient pneumonitis (less frequently than with Ascaris)
- epigastric pain & diarrhea may accompany early intestinal phase
Laboratory
- diagnosis is made by recovery of eggs in the feces
- eggs measure 40 by 60 um & are oval in shape
- rhabditiform larvae may be observed if eggs allowed to hatch after a delay in examination
- complete blood count (CBC)
- microcytic, hypochromic anemia with chronic infection
- eosinophilia with migratory phase
- serum albumin: hypoalbuminemia
Management
- the major consequence of chronic hookworm infection is iron deficiency anemia
- antihelmintic agents
- ferrous gluconate 320 mg PO TID
More general terms
Additional terms
References
- ↑ Clinical Diagnosis & Management by Laboratory Methods, 19th edition, J.B. Henry (ed), W.B. Saunders Co., Philadelphia, PA. 1996, pg 1285-86
- ↑ Harrison's Principles of Internal Medicine, 13th ed. Isselbacher et al (eds), McGraw-Hill Inc. NY, 1994, pg 917-18
- ↑ 3.0 3.1 Grimm L What's Eating You: 12 Common Intestinal Parasites. Medscape. November 25, 2019 https://reference.medscape.com/slideshow/intestinal-parasites-6010996
- ↑ 4.0 4.1 Grim L You've Got Worms! Common Intestinal Parasites Medscape. Jan 23, 2023 https://reference.medscape.com/slideshow/intestinal-parasites-6014593