Thiele E A, Sorensen R E, Gazzinelli A, Minchella D J
Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA.
Int J Parasitol. 2008 Mar;38(3-4):389-99. doi: 10.1016/j.ijpara.2007.07.011. Epub 2007 Aug 6.
The digenean trematode Schistosoma mansoni is responsible for chronic schistosomiasis worldwide, and in Brazil alone an estimated 35 million people are at risk. To evaluate epidemiological patterns among human definitive hosts, we assessed genetic diversity and population subdivision of S. mansoni infrapopulations in human hosts from the highly endemic village of Virgem das Graças in the state of Minas Gerais, Brazil. We believe this is the largest such survey to date. Genetic diversity of parasites, measured over eight polymorphic microsatellite loci, was relatively high and standard measures of inbreeding indicated that the population was panmictic. Furthermore, there was no significant isolation-by-distance of parasite infrapopulations, and measures of population subdivision indicated significant but low to moderate levels of population differentiation. We conclude that patients within this village sample from a broad range of schistosome genetic diversity and effectively act as "genetic mixing bowls" for the parasites. These results contrast with those previously observed in the Brazilian village of Melqui ades and thus provide the opportunity for comparisons of environmental and epidemiological differences that are likely to influence host-parasite coevolution and parasite transmission.
双口吸虫曼氏血吸虫在全球范围内引发慢性血吸虫病，仅在巴西就估计有3500万人面临感染风险。为了评估人类终宿主中的流行病学模式，我们对巴西米纳斯吉拉斯州高度流行的维尔京达斯格拉西亚斯村人类宿主中的曼氏血吸虫种群内的遗传多样性和种群细分进行了评估。我们认为这是迄今为止规模最大的此类调查。通过八个多态微卫星位点测量的寄生虫遗传多样性相对较高，近交的标准测量表明该种群是随机交配的。此外，寄生虫种群内没有显著的距离隔离，种群细分测量表明种群分化程度显著但较低至中等。我们得出结论，该村庄样本中的患者来自广泛的血吸虫遗传多样性范围，并有效地充当了寄生虫的“基因混合碗”。这些结果与之前在巴西梅尔基阿德斯村观察到的结果形成对比，从而为比较可能影响宿主 - 寄生虫共同进化和寄生虫传播的环境和流行病学差异提供了机会。
