Hookworm

Pathophysiology: Filariform (L3) larvae in fecally contaminated soil penetrate the skin, enter venous circulation, travel to the lungs, are coughed up and swallowed, and mature into adults in the small intestine. Adult worms attach to the intestinal mucosa using cutting plates (Necator) or teeth (Ancylostoma) and feed on blood, causing chronic blood loss leading to iron-deficiency anemia and hypoproteinemia. Eggs are passed in feces and hatch in soil, releasing rhabditiform larvae that molt into infective filariform larvae.

Clinical features: Initial skin penetration causes pruritic maculopapular rash ("ground itch"). Larval migration through lungs may cause transient cough, wheezing, and eosinophilia (Loeffler-like syndrome). Chronic intestinal infection leads to abdominal pain, diarrhea, and signs of iron-deficiency anemia (fatigue, pallor, koilonychia) and, in children, growth retardation and cognitive impairment due to malnutrition.

Diagnosis: Identification of oval, thin-shelled eggs with a clear space between shell and developing embryo in stool ova and parasite exam. Peripheral eosinophilia is common during larval migration.

Treatment: Albendazole or mebendazole (benzimidazoles that inhibit microtubule formation in helminths). Iron supplementation is given for anemia.

Prevention: Wearing shoes, improved sanitation, and proper disposal of human feces to prevent soil contamination.

High-yield associations: Necator americanus is more prevalent worldwide, while Ancylostoma duodenale is more common in parts of Asia and can also be transmitted orally. Hookworm infection is a classic cause of iron-deficiency anemia in endemic tropical/subtropical regions, distinguishing it from other causes like menorrhagia or GI malignancy in different populations.