加州大学的一组研究者近日在《美国国家科学院院刊》(Proceedings of the National Academy of Sciences)发表论文称,引起疟疾的疟原虫是由16世纪的非洲奴隶交易被引进南美洲的。
多年来,关于疟疾是如何进入南美的这一论题一直争论不休,有人认为疟疾是在数千年前由鸟类迁徙而跨国大西洋的,而该研究团队的这一发现有力地驳斥了上述理论。
为研究清楚南美洲疟原虫的根源,该研究小组搜集了南美洲、中亚、非洲鸡东南亚17个国家的被感染者的血液标本,然后对每一份标本进行了DNA分析,并对所有标本的分析结果进行比对。随后,研究者对蚊子的代数进行了估计,来计算南美最早出现疟疾的时间。
为了降低估算的不精确性,研究者使用蚊子每一代的最长时间和最短时间进行计算,即每年12代和每年6代。使用每年12代的计算结果是,疟疾约217至495年前在南美出现;使用每年6代的计算结果是,疟疾约434至900年前出现在南美。
第一个出现疟疾的地方在南美的北部,如墨西哥、哥伦比亚等,其估算时间与西班牙奴隶主到南美进行奴隶交易的时间吻合,而另外一个地方在南美南部,其估算时间与葡萄牙奴隶主到巴西进行奴隶交易的时间吻合。
因此,该团队认为疟疾是随着欧洲奴隶主到南美进行奴隶交易而出现的,当时这些携带有疟原虫的非洲奴隶们被贩卖到南美从事稀有金属的开采和甘蔗种植工作。(生物谷bioon.com)
doi:10.1073/pnas.1119058109
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Multiple independent introductions of Plasmodium falciparum in South America
Erhan Yalcindag, Eric Elguero, Céline Arnathau, Patrick Durand, Jean Akiana, Timothy J. Anderson, Agnes Aubouy, François Balloux, Patrick Besnard, Hervé Bogreau, Pierre Carnevale, Umberto D'Alessandro, Didier Fontenille, Dionicia Gamboa, Thibaut Jombart, Jacques Le Mire, Eric Leroy, Amanda Maestre, Mayfong Mayxay, Didier Ménard, Lise Musset, Paul N. Newton, Dieudonné Nkoghé, Oscar Noya, Benjamin Ollomo, Christophe Rogier, Vincent Veron, Albina Wide, Sedigheh Zakeri, Bernard Carme, Eric Legrand, Christine Chevillon, Francisco J. Ayalas,François Renaud , and Franck Prugnolle
The origin of Plasmodium falciparum in South America is controversial. Some studies suggest a recent introduction during the European colonizations and the transatlantic slave trade. Other evidence—archeological and genetic—suggests a much older origin. We collected and analyzed P. falciparum isolates from different regions of the world, encompassing the distribution range of the parasite, including populations from sub-Saharan Africa, the Middle East, Southeast Asia, and South America. Analyses of microsatellite and SNP polymorphisms show that the populations of P. falciparum in South America are subdivided in two main genetic clusters (northern and southern). Phylogenetic analyses, as well as Approximate Bayesian Computation methods suggest independent introductions of the two clusters from African sources. Our estimates of divergence time between the South American populations and their likely sources favor a likely introduction from Africa during the transatlantic slave trade.