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Mwea和内罗毕的肯尼亚医学研究所（KEMRI）进行，与Gerald Mkoji博士合作，作为NIH申请R01 AI044913“肯尼亚西部曼氏血吸虫的进化流行病学”的延伸，该申请由新墨西哥大学Eric S. Loker担任PI。该赠款的主要目的之一是开发基于微卫星的强大新技术，以揭示人类宿主体内的血吸虫生物学，并特别侧重于成人受试者和维多利亚湖沿岸的传播焦点。在父母赠款开发的技术基础上，我们将补充并扩大赠款的影响，将这些技术应用于Mwea的学童，这些学童参加了东部和南部非洲国际寄生虫控制中心（esacacpac）的Charles Mwandawiro博士指导的一项研究。该中心是在日本政府的支持下，通过日本国际协力机构（JICA）于2001年在KEMRI成立的。曼氏S. mansoni在Mwea的传播是以溪流为基础的，因此代表了该寄生虫存在于撒哈拉以南非洲大部分地区的环境。利用多重PCR扩增从23名感染儿童的粪便样本中获得的马氏血吸虫个体的13个微卫星位点，我们将检验与人类宿主血吸虫生物学有关的基本假设。我们将测试曼氏梭菌的遗传多样性（通过测量等位基因丰富度来评估）是否随着受试者年龄（6 - 14岁）和感染强度（1 - 400个卵/克粪便）的增加而增加，以及蠕虫种群是否由于感染机会有限而表现出克隆迹象。还将确定每个儿童之间以及来自特定村庄或学校的儿童之间曼索尼血吸虫种群的遗传差异程度。作为日本国际协力机构项目的一部分，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拥有的mansoni种群遗传组成的影响。此外，JICA项目的设计允许在儿童如预期再次感染的情况下对其进行重新治疗，因此我们还将在一次或多次重新治疗后监测微型基因型。由于针对儿童的类似治疗方案目前在非洲广泛开展，我们必须开发这些方法，作为监测控制方案效果和可能出现的耐药性的有力途径。这项FIRCA提案还将使我们能够对涉及不同年龄和生活在完全不同的传播环境中的人类受试者的父母补助金的结果进行深刻的比较。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，其中许多人因这种疾病而严重发病（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吡喹酮治疗。鉴于目前的单维控制方法，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mansoni的进化史和种群生物学，这才有可能。利用新技术，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等方面描述人类血吸虫种群，并监测新蠕虫的招募过程和耐药性的进化。这些信息将有助于了解血吸虫的传播动态、新性状（如耐药性）的传播以及种群动态。

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.