Evo-epidemiology of Scistosoma mansoni in children in Kenya

描述(由申请人提供)：这项研究将主要在肯尼亚的Mwea和内罗毕的肯尼亚医学研究所(KEMRI)与Gerald Mkoji博士合作进行，作为NIH题为“肯尼亚西部曼氏血吸虫的Evo-流行病学”的申请R01 AI044913的延伸，新墨西哥大学的Eric S.Loker担任私人投资。家长赠款的主要目标之一是开发强有力的基于微卫星的新技术，以揭示人类宿主中的血吸虫生物学，并特别关注维多利亚湖沿岸的成人受试者和传播点。在家长赠款开发的技术的基础上，我们将补充和扩大其影响，将这些技术应用于MWEA的学童群体，这些学生参加了由东部和南部非洲国际寄生虫控制中心的Charles Mwandawiro博士领导的一项研究，该研究是在日本政府的支持下，通过日本国际协力事业团于2001年在KEMRI建立的。Mwea地区曼氏葡萄球菌的传播是以溪流为基础的，因此代表了这种寄生虫在撒哈拉以南非洲大部分地区存在的环境。通过多重聚合酶链式反应扩增从23名感染儿童的粪便样本中获得的13个曼氏血吸虫毛虫微卫星基因座，我们将检验与人体血吸虫生物学有关的基本假设。我们将测试曼氏沙门氏菌的遗传多样性(通过等位基因丰富度评估)是否随着受试者的年龄(6至14岁)和感染强度(从1到400个卵/克粪便)而增加，以及蠕虫种群是否由于感染机会有限而表现出克隆迹象。还将确定曼氏血吸虫种群在每个儿童和来自特定村庄或学校的儿童之间的基因差异程度。作为日本国际协力事业团伞式项目的一部分，每个被研究的儿童都将接受吡喹酮治疗，我们将评估治疗对他们所庇护的曼氏葡萄球菌种群遗传构成的影响。此外，JICA项目的设计允许在儿童如预期的那样再次感染时对他们进行再次治疗，因此我们还将监测一次或可能多次再次治疗后的毛滴虫基因类型。由于类似的针对儿童的治疗方案现在在非洲很普遍，我们必须开发这些方法，作为监测控制方案的有效性和可能出现的耐药性的有效方法。FIRCA的这项建议还将使我们能够与父母资助的结果进行有洞察力的比较，该资助涉及不同年龄和生活在根本不同的传播环境中的人类受试者。公共卫生相关性：血吸虫病是一种被忽视的寄生虫病，全世界估计有2亿人感染，许多人因这种疾病而患有严重的疾病(Crompton，1999；Chitsulo等人)。2000)。目前，唯一得到广泛认可的控制血吸虫病的方法是用吡喹酮(PZQ)治疗。鉴于目前的一维控制方法，我们需要更好地监测蠕虫生物学的变化以及我们控制它们的努力。只有更详细地了解曼氏血吸虫的进化史和种群生物学，才有可能做到这一点。利用新的技术，我们提出的研究将从遗传多样性、遗传结构和克隆基因型的存在方面表征人类体内的血吸虫种群，并监测新蠕虫的招募过程和耐药性的进化。这些信息将对了解血吸虫的传播动力学、新特征的传播(如抗药性)和种群动态有价值。

DESCRIPTION (provided by applicant): This research will be done primarily in Kenya at the Kenya Medical Research Institute (KEMRI) in Mwea and Nairobi, in collaboration with Dr. Gerald Mkoji, as an extension of NIH application R01 AI044913 entitled "Evo-epidemiology of Schistosoma mansoni in western Kenya" for which Eric S. Loker, University of New Mexico, serves as PI. The parent grant has as one of its primary aims the development of robust new microsatellite-based techniques for revealing the biology of schistosomes in the human host, and focuses particularly on adult human subjects and foci of transmission along the shores of Lake Victoria. Building on the techniques developed in the parent grant, we will complement and expand its impact by applying these techniques to a population of schoolchildren in Mwea who are enrolled in a study directed by Dr. Charles Mwandawiro of the Eastern and Southern Africa Centre of International Parasite Control (ESACIPAC) which was established at KEMRI in 2001 with the support of the Japanese Government, through the Japan International Cooperation Agency (JICA). Transmission of S. mansoni in Mwea is stream-based and is thus representative of the setting in which this parasite exists in much of sub-Saharan Africa. Using multiplex PCR amplification of 13 microsatellite loci from individual S. mansoni miracidia obtained from fecal samples from ~23 infected children, we will test fundamental hypotheses relating to schistosome biology in the human host. We will test whether S. mansoni genetic diversity (as assessed by measures of allelic richness) increases with subject age (aged 6 to 14) and infection intensity (ranging from 1 to >400 eggs/gram of feces), and whether worm populations exhibit signs of clonality as a result of restricted opportunities for infection. The extent to which S. mansoni populations are genetically differentiated among each child and among children from a particular village or school will also be determined. Each child to be studied will be treated with praziquantel as part of the umbrella JICA project, and we will assess the impact of treatment on the genetic composition of the S. mansoni populations they harbor. Furthermore, the design of the JICA project allows for retreatment of children should they become reinfected as expected, so we will also monitor miracidial genotypes following one and possibly more re-treatments. As similar treatment programs targeting children are widespread in Africa now, it is imperative that we develop these approaches as powerful ways to monitor the efficacy of the control programs and the possible emergence of resistance. This FIRCA proposal will also allow us to make insightful comparisons with the results of the parent grant involving human subjects of different age and living in fundamentally different circumstances of transmission. PUBLIC HEALTH RELEVANCE: Schistosomiasis is a neglected parasitic disease that infects an estimated 200 million people world wide with many suffering from severe morbidity due to this disease (Crompton, 1999; Chitsulo et al. 2000). At present, the only widely endorsed means for controlling schistosomiasis is treatment with praziquantel (PZQ). Given the current one dimensional approach to control, we need to better monitor changes in the biology of the worms and our efforts to control them. This will only be possible with a more detailed understanding of the evolutionary history and population biology of S. mansoni. Using novel techniques, our proposed research will characterize schistosome populations within humans in terms of genetic diversity, genetic structuring, and presence of clonal genotypes as well as monitor the recruitment process of new worms and the evolution of drug resistance. This information will be valuable for understanding transmission dynamics, spread of novel traits such as drug resistance, and population dynamics of schistosomes.