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''Plasmodium knowlesi'' is a primate malaria parasite commonly found in Southeast Asia. It causes malaria in long-tailed macaques (''Macaca fascicularis''), but it may also infect humans, either naturally or artificially. ''Plasmodium knowlesi'' is the sixth major human malaria parasite (following the division of ''Plasmodium ovale'' into 2 species). It may cause severe malaria as indicated by its asexual erythrocytic cycle of about 24 hours, with an associated fever that typically occurs at the same frequency (i.e. the fever is quotidian).〔 This is an emerging infection that was reported for the first time in humans in 1965.〔 It accounts for up to 70% of malaria cases in certain areas in South East Asia where it is mostly found. This parasite is transmitted by the bite of an ''Anopheles'' mosquito.〔 ''Plasmodium knowlesi'' has health, social and economic consequences for the regions affected by it. ==History of discovery== The first person to see ''P. knowlesi'' was probably the Italian Giuseppe Franchiti in 1927 when he was examining the blood of ''Macaca fascicularis'' and he noted that it differed from ''Plasmodium cynomolgi'' and ''Plasmodium inui''.〔Franchini G (1027) Su di un plasmodio pigmentato di una scimmia. Arch Ital Sci Med Colon 8:187–90〕 It was later seen by Campbell in 1931 in a long-tailed macaque imported from Singapore to the Calcutta School of Tropical Medicine and Hygiene in India. Campbell was interested in kala azar and was working under Napier. Napier inoculated the strain into three monkeys, one of which was a rhesus macaque (''Macaca mulatta''), which developed a fulminating infection. Knowing that the Protozoological Department were looking for a monkey malaria strain, they handed the original infected monkey to Biraj Mohan Das Gupta, who was the assistant of Robert Knowles. Dr Das Gupta maintained the species by serial passage in monkeys until Dr Knowles returned from leave. In 1932, Knowles and Das Gupta described the species in detail for the first time and showed that it could be transmitted to man by blood passage, but failed to name it. It was named by Sinton and Mulligan in 1932 after Dr Knowles. From early in the 1930s to 1955, ''P. knowlesi'' was used as a pyretic agent for the treatment of patients with neurosyphillis.〔 In 1957, it was suggested by Garnham et al. that ''P. knowlesi'' could be the fifth species capable of causing endemic malaria in humans. In 1965, the first case of a naturally occurring infection of knowlesi malaria in humans was reported in an American man who had returned after working in the jungle in peninsular Malaysia. Although the infecting parasite was initially identified as ''P. falciparum'', one day later it was then identified as ''P. malariae'' and it was only confirmed to be ''P. knowlesi'' after infected blood was used to inoculate Rhesus monkeys.〔 A second report emerged in 1971 about the natural infection of a man in Malaysia with ''Plasmodium knowlesi'' followed by the description of a large focus of human infections in the Kapit Division of Sarawak, Malaysian Borneo.〔 This was made possible due to the development of molecular detection assays which could differentiate between ''Plasmodium knowlesi'' and the morphologically similar ''Plasmodium malariae.'' Since 2004, there has been an increasing number of reports of the incidence of ''P. knowlesi'' among humans in various countries in South East Asia, including Malaysia, Thailand, Singapore, the Philippines, Vietnam, Myanmar and Indonesia. Work with archival samples has shown that infection with this parasite has occurred in Malaysia at least since the 1990s and it is now known to cause 70% of the malaria cases in certain areas of Sarawak. 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「Plasmodium knowlesi」の詳細全文を読む スポンサード リンク
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