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''Trypanosoma cruzi'' is a species of parasitic euglenoid protozoan. Amongst the protozoa, the trypanosomes characteristically bore tissue in another organism and feed on blood, and lymph. This behaviour causes disease or the likelihood of disease that varies with the organism: for example, trypanosomiasis in humans (Chagas disease in South America and sleeping sickness in Africa), dourine and surra in horses, and a brucellosis-like disease in cattle. Parasites need a host body and the haematophagous insect triatomine (descriptions "assassin bug", "cone-nose bug", and "kissing bug") is the major vector in accord with a mechanism of infection. The triatomine likes the nests of vertebrate animals for shelter, where it bites and sucks blood for food. Individual triatomines infected with protozoa from other contact with animals transmit trypanosomes when the triatomine deposits its faeces on the host's skin surface and then bites. Penetration of the infected faeces is further facilitated by the scratching of the bite area by the human or animal host. Trypanosomiasis in humans progresses with the development of the trypanosome into a trypomastigote in the blood and into an amastigote in tissues. The acute form of trypanosomiasis is usually unnoticed, although it may manifest itself as a localized swelling at the site of entry. The chronic form may develop 10 to 20 years after infection and affect internal organs (e.g., the heart, the oesophagus, the colon, and the peripheral nervous system). Affected people may die from heart failure. Acute cases are treated with nifurtimox and benznidazole, but no effective therapy for chronic cases is currently known. ==Life cycle== The ''Trypanosoma cruzi'' life cycle starts in an animal reservoir, usually mammals, wild or domestic, including humans. A triatomine bug serves as the vector. While taking a blood meal, it ingests ''T. cruzi''. In the triatomine bug (''Triatoma infestans'') the parasite goes into the epimastigote stage, making it possible to reproduce. After reproducing through binary fission, the epimastigotes move onto the rectal cell wall, where they become infectious. Infectious ''T. cruzi'' are called metacyclic trypomastigotes. When the triatomine bug subsequently takes a blood meal from a human, it defecates. The trypomastigotes are in the feces and are capable of swimming into the host's cells using flagella, a characteristic swimming tail dominant in the Euglenoid class of protists.〔 〕 The trypomastigotes enter the human host through the bite wound or by crossing mucous membranes. The host cells contain macromolecules such as laminin, thrombospondin, heparin sulphate, and fibronectin that cover their surface. These macromolecules are essential for adhesion between parasite and host and for the process of host invasion by the parasite. The trypomastigotes must cross a network of proteins that line the exterior of the host cells in order to make contact and invade the host cells. The molecules and proteins on the cytoskeleton of the cell also bind to the surface of the parasite and initiate host invasion.〔 When they enter a human cell, they become amastigotes. This is another reproductive stage. After reproducing through binary fission until a large amount of amastigotes are present in a cell, pseudocysts are formed there. The amastigotes then turn back into trypomastigotes, and the cell bursts. The trypomastigotes swim along to either infect other cells or get sucked up by other reduviid bugs. 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「trypanosoma cruzi」の詳細全文を読む スポンサード リンク
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