Hookworm disease is widespread in tropical and subtropical areas lacking adequate sanitary disposal of human wastes. It causes iron-deficient anemia and malnutrition. Larvae in soil are infective for several weeks. Larvae infect by penetrating the skin, usually the feet.
CASES/YEAR
288 (US); 576,000,000 (Global)
OTHER NAMES
Necator americanus infection; Ancylostoma duodenale infection;
INCUBATION
A few weeks to many months for symptoms to develop; [CCDM]
INITIAL SYMPTOMS
Patients with light infections are usually asymptomatic. "Ground itch" (papule or vesicle) may occur at the time of larva penetration of the skin. Epigastric pain, diarrhea, and eosinophilia occur about 30-45 days later. [PPID, 8th Ed, p. 3203]
PRECAUTIONS
"Infected people can contaminate soil for several years in the absence of treatment. Under favorable conditions, larvae remain infective in soil for several weeks." [CCDM, p. 296]
COMMENTS
EPIDEMIOLOGY:
Hookworm disease, an intestinal nematode infection, is widespread in tropical and subtropical areas lacking adequate sanitary disposal of human wastes. The disease affects more than 10% of the world's population and is a significant cause of iron-deficient anemia and malnutrition. Larvae in soil are infective for several weeks. Larvae infect by penetrating the skin, usually the feet. Wearing shoes prevents infections by N. americanus, but not all infections by A. duodenale, which can infect by ingestion. Humans are the only reservoirs for both species of hookworm; therefore, effective sanitation will prevent infections.
FINDINGS:
The degree of anemia reflects the severity of infection. Patients with heavy infections may have diarrhea, epigastric ulcer-like pain, and stool positive for occult blood. During the lung-migration phase, larvae invade the lungs and may cause transient tracheitis with coughing, wheezing, fever, and blood-tinged sputum. Marked eosinophilia is associated with larval migration. Otherwise, eosinophilia is low or absent. A rash, "ground itch," may appear at the site of the penetrating larvae. Urticaria may be seen during the lung-migration phase. Other findings that sometimes occur: constipation, diarrhea, fatigue, dizziness, and pneumonia. Vomiting is a symptom after ingestion of A. duodenale. The sites of skin entry may appear as vesicles or pustules. Overwhelming infection can cause coma and death. [Cohen, p. 991; ID, p. 1533, 2359-60; Guerrant, p. 799-804, 943, 961; CCDM, p. 295-7, 613; PPID, p. 3439-40; Cecil, p. 2130]
DIAGNOSTIC
Microscopic exam of feces; Concentration techniques may be needed to detect very light infections. [PPID, 8th Ed, p. 3204]
SCOPE
Prevalent in the tropics and subtropics; [PPID, p. 3199]
SIGNS & SYMPTOMS
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>fatigue, weakness
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>fever
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E pharyngitis
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G abdominal pain
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G blood in stool
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G constipation
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G diarrhea
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G nausea, vomiting
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H anemia
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H eosinophilia
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N headache
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R cough
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R dyspnea
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R hemoptysis
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R wheezing
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S papules or plaques
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S pustule
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S skin blister or vesicles
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S urticaria
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S skin lesion, linear or serpiginous
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X lung infiltrates
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*pneumonia
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*pneumonitis
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*stupor, coma
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*weight loss
ENTRY
Ingestion, Skin or Mucous Membranes (Includes Conjunctiva)
SOURCE
Person-to-Person, Human Fecal-Oral, Fecally Contaminated Soil, Soil or Dust (Ingesting or Inhaling), Eating Contaminated Food, Eating Contaminated Produce
RESERVOIR
Cats, Dogs, Human
RISK FACTORS
- Ingest infectious agents in food/water
- Walk barefooted in contaminated soil
REFERENCES FOR CASES/YEAR
1. (US) A control program established by the Rockefeller Commission in 1909 virtually eliminated transmission in the US; Guesstimate: 0.0000005 X global cases/yr = 288; (See Ascariasis.)
2. (Global) 1.5 billion (Ascariasis, Trichuriasis, and hookworm infections (N. americanus & A. duodenale); [Fact sheets from WHO 2013] Global prevalence 576 million; [Harrison ID, p. 1132t] About 450 million chronically infected; [PPID, p. 3439]