Characterization of Trypanosoma cruzi in southern Ecuador

描述(由申请人提供)：有效的全国恰加斯病控制方案的设计取决于对在克氏锥虫的维持和传播中起作用的不同因素的了解。清楚地了解这种寄生虫的传播动态及其与病媒和宿主物种的关系，对于设计旨在阻止向人类传播的控制措施至关重要。南美洲北部主要的克氏锥虫病媒物种占据了海岛和国内的栖息地。随着海尔夫传播者的居留，周围环境中的血源成为海尔夫斯传播者和国内传播周期之间的桥梁。海岛和共生载体与哺乳动物宿主之间的相互作用有利于寄生虫菌株的持续交换及其向人类的传播。我们推测，克氏锥虫II(TCII)谱系将在国内生境中占主导地位，随着生境从国内生境转移到周缘生境再到森林生境，TCI谱系将变得更加普遍。此外，我们还假设，在厄瓜多尔南部的国内、周缘和海岛生境中，从不同宿主分离的寄生虫之间存在很高的遗传相似性，表明寄生虫交换频繁。我们将通过以下方式验证这些假设：(1)对厄瓜多尔南部不同宿主的克氏锥虫分离株进行分子特征分析，并确定它们的遗传相似性；(3)最后，为了了解影响寄生虫种群间基因流动的生物和非生物因素，我们建议检验遗传距离和地理距离之间的关系。为了实现这些目标，我们将在厄瓜多尔南部洛哈省不同生态区的一组农村社区收集三聚氰胺、哺乳动物水库和人类血液。我们将通过PCR扩增微小外显子基因24Sa rRNA和18Sa rRNA的非转录间隔区，从这些来源分离和鉴定克鲁兹毛滴虫。此外，我们将通过分析多达11个多态微卫星座位，结合系统发育树的构建，确定感染不同宿主的寄生虫种群之间的遗传流动。最后，我们将使用地统计学技术来检验不同克氏锥虫分离株的遗传距离和空间距离之间的关系。除了帮助了解克氏锥虫的传播周期外，该项目还将为本科生、研究生和医学生提供极好的培训机会，同时加强PI的研究计划和加强院校研究环境，从而实现学术研究促进奖(AREA)的目标。该项目的成果将增加现有的基本生物学知识库，并有助于国家过敏和传染病研究所(NIAID)了解和预防传染病的使命，从而改善美国和世界各地数百万人的健康。公共卫生相关性：感染克氏锥虫寄生虫威胁着拉丁美洲的1亿人，并构成该地区心脏病的主要原因。拟议的项目将研究厄瓜多尔南部这种寄生虫的传播周期，这是南美洲一大片地区的代表，过去几乎没有研究过影响克氏锥虫传播的生物因素。拟议的研究将扩大关于安第斯地区克氏锥虫传播生物学的知识，这对于建立旨在阻止寄生虫传播到人类群体的控制方案至关重要。

DESCRIPTION (provided by applicant): The design of effective country-wide Chagas disease control programs depend on the understanding of the different factors that play a role in the maintenance and transmission of Trypanosoma cruzi. A clear comprehension of the transmission dynamics of this parasite and its relationship to its vector and reservoir species is crucial for the design of control measures aimed at stopping transmission to humans. The predominant T. cruzi vector species in Northern South America occupy both sylvatic and domestic habitats. As sylvatic vectors become domiciliated, blood sources in the peridomestic environment serve as a bridge between the sylvatic and domestic cycles of transmission. Interaction between sylvatic and synanthropic vectors and mammalian reservoirs favors the constant exchange of parasite strains and their transmission to humans. We hypothesize that the T. cruzi II (TCII) lineage will predominate in domestic habitats, and the TCI lineage will become more prevalent as habitats move from domestic to peridomestic to sylvatic habitats. In addition, we also hypothesize that there is high genetic similarity among parasites isolated from different hosts collected in the domestic, peridomestic and sylvatic habitats in Southern Ecuador, indicating frequent parasite exchange. We will test these hypotheses by: (1) molecularly characterizing T. cruzi isolates from different hosts at domestic, peridomestic and sylvatic environments in Southern Ecuador and (2) determining their genetic similarity; (3) Finally, in order to understand the biotic and abiotic factors that influence gene flow between parasite populations, we propose to examine the relationship between genetic distance and geographical distance. To accomplish these aims we will collect triatomines, mammalian reservoirs and human blood in a set of rural communities located in different ecological zones within Loja Province, in Southern Ecuador. We will isolate and molecularly characterize T. cruzi from these sources using PCR amplification of the non-transcribed spacer regions of the mini-exon gene, 24Sa rRNA and 18Sa rRNA. In addition we will determine the genetic flow among parasite populations infecting the different hosts by analyzing up to 11 polymorphic microsatellites loci in conjunction with the construction of phylogenetic trees. Finally, we will use geostatistical techniques to examine the relationship between the genetic and spatial distances of the various T. cruzi isolates. In addition to helping understand the transmission cycles of T. cruzi, this project will provide excellent training opportunities for undergraduate, graduate and medical students while fortifying the PI's research program and strengthening the institutional research environment, thereby fulfilling the goals of Academic Research Enhancement Award (AREA). The results of this project will add to the existing basic biological knowledge base and contribute towards the National Institute of Allergy and Infectious Diseases' (NIAID) mission of understanding and preventing infectious diseases and thus, improving the health of millions of people in the United States and around the world. PUBLIC HEALTH RELEVANCE: Infection with the parasite Trypanosoma cruzi threatens 100 million people in Latin America, and constitutes a major cause of heart disease in this region. The proposed project will examine the transmission cycles of this parasite Southern Ecuador, which is representative of a vast region of South America where the biological factors affecting T. cruzi transmission have been scarcely studied in the past. The proposed research will expand the knowledge regarding the biology of T. cruzi transmission in the Andean region, which is paramount for the establishment of control programs aimed at stopping transmission of the parasite to human populations.