Hookworm infection
Hookworm infection, caused by Necator americanus or Ancylostoma duodenale, is treated with albendazole 400 mg single dose plus iron repletion; it is acquired when soil larvae penetrate bare skin and produces microcytic iron-deficiency anemia from chronic intestinal blood loss by adult worms attached to the small bowel mucosa.
- Topic reviewThe full article, organized the way the exam asks it.
- ABIM-format MCQsVignettes with an explanation for every wrong answer.
- Key factsThe numbers and thresholds worth memorizing, up front.
- AI tutorMedBrain answers the question you're stuck on.
What this article covers
- Overview
Skin-penetrating intestinal nematode infection: hookworm infection is caused by Necator americanus or Ancylostoma duodenale, acquired when infective larvae in contaminated soil penetrate intact skin, classically the bare feet.
- Epidemiology
One of the most prevalent soil-transmitted helminth infections worldwide, concentrated in tropical and subtropical regions with poor sanitation, mirroring the distribution of ascariasis and trichuriasis.
- Risk factors
Walking barefoot on soil contaminated with human feces: the dominant route of exposure, since larvae hatch from eggs deposited in soil and penetrate skin on contact.
- Pathophysiology
Larval skin penetration: filariform larvae in soil penetrate intact skin, producing local inflammation at the entry site.
- Clinical features
Ground itch at the skin entry site: pruritic, erythematous papulovesicular rash where larvae penetrated, typically the feet, occurring at the time of exposure.
- Differential diagnosis
Ascariasis: ingested (not skin-penetrating), and causes obstruction from a large worm mass rather than anemia; see ascariasis.
- Diagnosis
Confirmed by identifying hookworm eggs on stool ova and parasite microscopy, the standard confirmatory test; oval, thin-shelled eggs are seen, though Necator and Ancylostoma eggs cannot be reliably distinguished by microscopy alone.
- Management
Antihelminthic therapy: albendazole 400 mg PO as a single dose, first-line.
- Complications
Iron-deficiency anemia, ranging from mild to severe: the principal complication, driven by chronic blood loss proportional to worm burden.
- Prognosis
Excellent with antihelminthic treatment and iron repletion: anemia corrects over weeks to months once the worm burden is cleared and iron stores are replaced.
- Prevention
Wear shoes when walking on soil in endemic areas: the single most effective individual measure, since larvae penetrate through bare skin contact with contaminated ground.
Read the whole article
Subscribing to Internal Medicine opens every article, the full question bank and MedBrain, on the web, iPhone and Android.
Related articles
- Ascariasis (roundworm infection)
Ascariasis is fecal-oral infection with Ascaris lumbricoides, the largest intestinal nematode, treated with albendazole 400 mg single dose; it causes Loffler pulmonary eosinophilia during larval lung migration and, with heavy adult worm burden, intestinal, biliary, or pancreatic duct obstruction.
- Trichuriasis (whipworm infection)
Trichuriasis is fecal-oral infection of the colon with Trichuris trichiura (whipworm), treated with albendazole 400 mg daily for 3 days; light infection is often asymptomatic, while heavy pediatric worm burden causes chronic dysentery, growth impairment, and rectal prolapse.
- Strongyloidiasis
Strongyloides stercoralis is a soil-transmitted nematode uniquely capable of autoinfection, so it can persist for decades and, in a host started on glucocorticoids or otherwise immunosuppressed, progress to hyperinfection with gram-negative bacteremia; diagnosis is by stool larvae or serology and treatment is ivermectin.
- Toxocariasis
Toxocariasis is human infection with the dog or cat roundworm Toxocara canis or Toxocara cati, acquired by ingesting embryonated eggs, producing visceral larva migrans with hepatic, pulmonary, and eosinophilic disease or ocular larva migrans mimicking retinoblastoma. Diagnosis rests on compatible exposure and clinical findings plus Toxocara-specific serology, and treatment combines an antihelminthic with corticosteroids for organ-threatening inflammation.
- Pinworm infection (enterobiasis)
Pinworm infection (enterobiasis) is caused by the nematode Enterobius vermicularis and is the most common helminthic infection in children, presenting with perianal pruritus that is worse at night. Diagnosis is made by the cellophane tape test performed on first waking, and treatment is a single oral dose of albendazole, mebendazole, or pyrantel pamoate given to the patient and all household members, repeated after two weeks to break the autoinfection cycle.