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''Cryptosporidium parvum'' is one of several protozoal species that cause cryptosporidiosis, a parasitic disease of the mammalian intestinal tract. Primary symptoms of ''C. parvum'' infection are acute, watery, and non-bloody diarrhea. ''C. parvum'' infection is of particular concern in immunocompromised patients, where diarrhea can reach 10–15L per day. Other symptoms may include anorexia, nausea/vomiting and abdominal pain. Extra-intestinal sites include the lung, liver and gall bladder where it causes respiratory cryptosporidosis, hepatitis and cholecystitis.〔”Cryptosporidiosis.” Laboratory Identification of Parasites of Public Health Concern. CDC. 5 Sept 2007. Infection is caused by ingestion of sporulated oocysts transmitted by the faecal-oral route. In healthy human hosts, the median infective dose is 132 oocysts. The general ''C. parvum'' life cycle is shared by other members of the genus. Invasion of the apical tip of ileal enterocytes by sporozoites and merozoites causes pathology seen in the disease. Infection is generally self-limiting in immunocompetent people. In immunocompromised patients, such as those with AIDS or those undergoing immunosuppressive therapy, infection may not be self-limiting, leading to dehydration and, in severe cases, death. ==Detection== ''Cryptosporidium parvum'' oocysts are very difficult to detect and therefore diagnose. The oocysts in fecal samples would indicate if the parasite is present in the body but they have a very small size and so detection is made very difficult. Doing a fecal ELISA method to detect the presence of the parasite would eliminate the difficulty due to the small size and many other methods are unable to distinguish between past and present infections; something serological ELISA would not allow to distinguish.〔DuPont et al "The Infectivivty of Cryptosporidium parvum in healthy Volunteers" http://www.nejm.org/doi/pdf/10.1056/NEJM199503303321304〕 ''C. parvum'' is considered to be the most important waterborne pathogen in developed countries. The protozoa also caused the largest waterborne-disease outbreak ever documented in the United States, making 403,000 people ill in Milwaukee, Wisconsin in 1993.〔”Surveillance for Waterborne-Disease Outbreaks -- United States, 1993-1994” CDC. 1996. 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「Cryptosporidium parvum」の詳細全文を読む スポンサード リンク
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