Environmental influences on urban schistosomiasis transmission and elimination

今天，血吸虫病低度至中度流行国家管理血吸虫病的巨大挑战是 从控制疾病发展到根除疾病大多数努力都看到了流行率和强度的初步下降 其次是低水平的传播，如果被忽视，就会不断威胁到死灰复燃。人类移民 寄生虫种群的健康状况、潜在的耐药性、气候条件和人类粪便的水平 地表沃茨的污染都可能导致持久性。根除甚至消灭作为一个公共 健康问题可以被看作是导致灭绝努力。虽然灭绝和保护是 群体遗传学为管理做出了重要贡献， 在规划和决定寄生虫防治时，很少采用这种观点。在纵向 农村感染的治疗研究，人口遗传结构的分析表明，移民（基因 在低流行率下，广泛的药物管理不太可能促进 耐药性，持续性感染不太可能代表耐药性， 人口统计学和再感染可与持续性区分开来。通常被认为是一种农村疾病， 血吸虫病越来越多地在大城市地区被发现，85%的巴西人口 居住，从城市地区消除血吸虫病可能是一个更容易处理的问题，而不是从一个 农村地区。城市疫源地一般由较轻的感染组成，因此作为一个起点， 点此外，城市的卫生条件一般较好。最后，病灶清除更可能发生在感染的城市， 存在于小的“岛屿”中。S.在一个病例中发现了曼氏菌传播和人类感染， 在巴西巴伊亚的萨尔瓦多附近，一个有300万人口的城市，和其他社区的感染蜗牛。分析 的人口结构表明，甚至更大的空间碎片比农村网站。感染情况如何 以及人类、寄生虫和蜗牛种群如何随时间变化， 如何消除传播的影响。本提案将收集纵向人口统计数据， 巴西血吸虫病传播城市疫源地的寄生虫遗传学、软体动物学和环境数据。 两个社区的血吸虫病流行率将每年进行调查， 信息和血吸虫粪便卵，感染者将得到治疗。当地的水接触点也将 每月进行一次关于蜗牛感染、人类粪便污染和气候条件的调查。寄生虫 将对人口进行遗传表征和跟踪，并研究人类的空间和纵向分布。 将评估粪便污染和蜗牛数量，并将其与风险联系起来。人口、环境 气候数据将为解释寄生虫种群结构的变化提供背景。理解 寄生虫种群在压力下的反应将指导消灭的管理战略。

Today, the great challenge for management of schistosomiasis in countries with low to moderate endemicity is to move from morbidity control to eradication. Most efforts see initial reductions in prevalence and intensity followed by low-level transmission that constantly threatens resurgence if neglected. Human immigration, the health of the parasite population, potential drug resistance, climatic conditions and the level of human fecal contamination of surface waters can all contribute to persistence. Eradication or even elimination as a public health problem can be viewed as an effort to produce extinction. While extinction and conservation are subjects where population genetics have made important contributions for management, a population genetics perspective is rarely applied when planning and making decisions about parasite control. In longitudinal treatment studies of rural infections, an analysis of population genetic structure showed that immigration (gene flow) contributes little to persistence, at low prevalence widespread drug administration is not likely to promote drug resistance, persistent infections are unlikely to represent drug resistance, there are no host preferences by demographics and re-infection can be distinguished from persistence. Often considered a rural disease, schistosomiasis is increasingly being identified in large urban areas where 85% of the Brazilian population resides, and elimination of schistosomiasis from an urban area can be a more tractable problem than from a rural area. Urban foci in general consist of lighter infections and thus are nearer to elimination as a starting point. Also, urban sanitation is generally better. Finally, focal elimination is more likely in cities where infection exists in small "islands". An active site of S. mansoni transmission and human infection was identified in one neighborhood of Salvador, Bahia, Brazil, a city of 3 million, and infected snails in other neighborhoods. Analysis of population structure suggested even greater spatial fragmentation than in rural sites. How the infection is distributed within communities and how the human, parasite and snail populations change over time have implications for how transmission might be eliminated. This proposal will collect longitudinal demographic, parasite genetic, malacologic and environmental data from urban foci of schistosomiasis transmission in Brazil. Two neighborhoods where the prevalence of schistosomiasis will be surveyed yearly for demographic information and schistosome stool eggs, and those infected will be treated. Local water contact sites will also be surveyed monthly for snail infections, human fecal contamination and climatic conditions. Parasite populations will be genetically characterized and tracked, and the spatial and longitudinal distribution of human fecal contamination and snail populations will be assessed and related to risk. The demographic, environmental and climatic data will provide a context for interpreting changes in parasite population structure. Understanding the response of parasite populations under pressure will guide management strategies toward eradication.