Disease Information for Hookworm (Ancylostomiasis) disease: Definition

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  • One-fourth of the world"s population is infected with one of the two hookworm species (A duodenale and N americanus). Most infected individuals are asymptomatic; Hookworm disease develops from a combination of factors—a heavy worm burden, a prolonged duration of infection, and an inadequate iron intake—and results in iron-deficiency anemia and, on occasion, hypoproteinemia; Adult hookworms, which are 1 cm long, use buccal teeth (Ancylostoma) or cutting plates (Necator) to attach to the small-bowel mucosa and suck blood (0_2 mL/d per Ancylostoma adult) and interstitial fluid; The adult hookworms produce thousands of eggs daily; The eggs are deposited with feces in soil, where rhabditiform larvae hatch and develop over a 1-week period into infectious filariform larvae; Infective larvae penetrate the skin and reach the lungs by way of the bloodstream; There they invade alveoli and ascend the airways before being swallowed and reaching the small intestine; The prepatent period from skin invasion to appearance of eggs in the feces is about 6 to 8 weeks, but it may be longer with A duodenale; Larvae of A duodenale, if swallowed, can survive and develop directly in the intestinal mucosa; Adult hookworms may survive over a decade but usually live about 6 to 8 years for A duodenale and 2 to 5 years for N americanus; Epidemiology; A duodenale is prevalent in southern Europe, North Africa, and northern Asia, and N americanus is the predominant species in the western hemisphere and equatorial Africa; The two species overlap in many tropical regions, particularly Southeast Asia; In most areas, older children have the greatest incidence and intensity of hookworm infection; In rural areas where fields are fertilized with night soil, older working adults also may be heavily affected; Most hookworm infections are asymptomatic; Infective larvae may provoke pruritic maculopapular dermatitis ("ground itch") at the site of skin penetration as well as serpiginous tracks of subcutaneous migration (similar to cutaneous larva migrans) in previously sensitized hosts; Larvae migrating through the lungs occasionally cause mild transient pneumonitis, but this condition develops less frequently in hookworm infection than in ascariasis;

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