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Soil-transmitted helminthiasis (STH) is a type of helminth infections (helminthiasis) caused by different species of roundworms. It is caused specifically by those worms which are transmitted through soil contaminated with faecal matter and are therefore called soil-transmitted helminths. Three types of soil-transmitted helminthiasis can be distinguished: ascariasis, hookworm disease and trichuriasis. These three types of infection are therefore caused by the large roundworm ''A. lumbricoides; ''the hookworms'' ''Necator americanus'' or ''Ancyclostoma duodenale; and by the whipworm ''Trichuris trichiura ''respectively''. '' It has become the most common parasitic disease of humans worldwide. Approximately two billion people (about a third of global population) are infected as of the latest estimate, and four billion at risk, surpassing even the all-time most prevalent parasitic disease, malaria. The largest numbers of cases occur in impoverished rural areas of Subsaharan Africa, Latin America, Southeast Asia, and China. Its main cause, like for many types of helminth infections, is lack of sanitation, such as the practice of open defecation and lack of hygiene such as hand washing. It is regarded as one of the world's most important causes of intellectual and physical retardation. The helminthic disease is so named because the infection is transmitted through ingestion of the nematode eggs in the soil, which is contaminated through excrements. Therefore, the disease is most prevalent in warm and moist climates where sanitation and hygiene are poor and waters are unsafe, including the temperate zones during warmer months. STH is categorised among Neglected Tropical Diseases because it inflicts tremendous disability and suffering, which can be clinically treated and relatively easily be prevented (primarily through improved sanitation), yet negligible attention has been given for many years. It is now among the target diseases of ''London Declaration on Neglected Tropical Diseases'' (launched on 30 January 2012) to be controlled/eradicated by 2020. Simple prevention and control strategies are access to improved sanitation, public awareness on personal hygiene and health education. ==Signs and symptoms== Symptoms becomes evident only when the intensity of infection is relatively high. Thus the degree of negative outcomes is directly related to worm burden; more worms means greater severity of disease. 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「Soil-transmitted helminthiasis」の詳細全文を読む スポンサード リンク
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