A parasitic infection caused by the nematodes Ancylostoma duodenale and Necator americanus, resulting in hookworm disease. These infections are exceedingly common in tropical and developing countries, millions of people being aﬀected. Classically, A. duodenale occurred in the Far East, Mediterranean littoral, and Middle East, and N. americanus in tropical Africa, Central and South America, and the Far East; however, in recent years, geographical separation of the two human species is less distinct. In areas where standards of hygiene and sanitation are unsatisfactory, larvae (embryos) enter via intact skin, usually the feet. ‘Ground itch’ occasionally occurs as larvae enter the body. They then undergo a complex life-cycle, migrating through the lungs, trachea, and pharynx. Adult worms are 5–13 (mean 12) mm in length; their normal habitat is the small INTESTINE – especially the jejunum – where they adhere to the mucosa by hooks, thus causing seepage of blood into the lumen. A worm-pair produces large numbers of eggs, which are excreted in faeces; when deposited on moist soil they remain viable for many weeks or months. Clinical manifestations include microcytic hypochromic ANAEMIA, hypoalbuminaemia (low serum protein) and, in a severe case, OEDEMA. A chronic infection in childhood can give rise to physical, mental and sexual retardation. Treatment is with one of the benzimidazole compounds, usually mebendazole or albendazole; however, in developing countries, cheaper preparations are used, including tetrachloroethylene, bephenium hydroxynaphthoate, and pyrantel embonate. Anaemia usually responds to iron supplements; blood transfusion is rarely indicated.
Ancylostoma braziliensis A nematode infection of dogs, which in humans causes local disease (larva migrans) only, generally on the soles of the feet. It is usually acquired by walking on beaches contaminated with dog faeces in places such as the Caribbean.