Two Nonrecombining Sympatric Forms of the Human Malaria Parasite Plasmodium ovale Occur Globally
Two Nonrecombining Sympatric Forms of the Human Malaria Parasite Plasmodium ovale Occur Globally
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DOI：
10.1086/652240
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发表时间：
2010-05-15
影响因子：
6.4
通讯作者：
Polley, Spencer D.
中科院分区：
文献类型：
--
作者：
Sutherland, Colin J.;Tanomsing, Naowarat;Polley, Spencer D.
背景。人类疟疾是由属于疟原虫属 5 种的顶复门寄生虫引起的。卵形疟原虫感染分布广泛，但很少进行研究，并且由此产生的疾病负担尚不清楚。特定基因的二态性导致 P. ovale 寄生虫分为经典型和变异型。我们假设这些二态性代表不同的寄生虫物种。方法。对来自 12 个非洲国家和 3 个亚太国家的 55 个分离株进行了 6 个遗传性状的多位点序列分析。每个遗传特征都表现出完全的二态性，并且在两种类型之间完美分离。这两种类型均在来自加纳、尼日利亚、圣多美、塞拉利昂和乌干达的样本中被鉴定出来，并且之前在缅甸也有过描述。据估计，这两个谱系的分裂发生在 1.0 至 350 万年前的原始人类宿主中。结论。我们认为 P. ovale 包含 2 个非重组物种，它们分布在非洲和亚洲。我们推测可能导致这种物种形成的情况。此外，英国出现症状的卵形疟原虫感染的输入病例频率相对较高，这表明卵形疟疾引起的发病率被低估了。
Background. Malaria in humans is caused by apicomplexan parasites belonging to 5 species of the genus Plasmodium. Infections with Plasmodium ovale are widely distributed but rarely investigated, and the resulting burden of disease is not known. Dimorphism in defined genes has led to P. ovale parasites being divided into classic and variant types. We hypothesized that these dimorphs represent distinct parasite species.Methods. Multilocus sequence analysis of 6 genetic characters was carried out among 55 isolates from 12 African and 3 Asia-Pacific countries.Results. Each genetic character displayed complete dimorphism and segregated perfectly between the 2 types. Both types were identified in samples from Ghana, Nigeria, Sao Tome, Sierra Leone, and Uganda and have been described previously in Myanmar. Splitting of the 2 lineages is estimated to have occurred between 1.0 and 3.5 million years ago in hominid hosts.Conclusions. We propose that P. ovale comprises 2 nonrecombining species that are sympatric in Africa and Asia. We speculate on possible scenarios that could have led to this speciation. Furthermore, the relatively high frequency of imported cases of symptomatic P. ovale infection in the United Kingdom suggests that the morbidity caused by ovale malaria has been underestimated.