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The soil-transmitted helminths (also called geohelminths) are a group of intestinal parasites belonging to the class Nematoda that are transmitted primarily through contaminated soil. They are so called because they have a direct life cycle which requires no intermediate hosts or vectors, and the parasitic infection occurs through faecal contamination of soil, foodstuffs and water supplies. The adult forms are essentially parasites of humans, causing soil-transmitted helminthiasis (SHT), but also infect domesticated mammals. The juveniles are the infective forms and they undergo tissue-migratory stages during which they invade vital organs such as lungs and liver. Thus the disease manifestations can be both local and systemic. The geohelminths together present an enormous infection burden on humanity, amounting to 135,000 deaths every year, and persistent infection of more than two billion people. ==Types== Soil-transmitted helminths are caused by four groups of nematodes, namely *Ascaris (''Ascaris lumbricoides'') *Whipworm (''Trichuris trichiura'') *Hookworms (''Ancylostoma duodenale'' and ''Necator americanus'') *Pinworm/threadworm (''Strongyloides stercoralis'') 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「geohelminth」の詳細全文を読む スポンサード リンク
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