Environmental influences on urban schistosomiasis transmission and elimination

今天，在低至中等地方性国家管理血吸虫病面临的巨大挑战是 从发病率控制转向根除。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、潜在的抗药性、气候条件和人类排泄物水平 地表水的污染都可能有助于持久化。作为公众的根除甚至消灭 健康问题可以被视为一种导致灭绝的努力。虽然灭绝和保护是主题 其中种群遗传学对管理做出了重要贡献，一种种群遗传学 在规划和做出有关寄生虫控制的决策时，很少使用视角。纵向的 农村感染的治疗研究，对人口遗传结构的分析表明，移民(基因 流动)对持久性几乎没有贡献，在低流行率的情况下，广泛的药物管理不太可能促进 耐药性，持续感染不太可能代表耐药性，没有宿主偏好的 人口统计数据和再次感染可以与持续性区分开来。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，那里85%的巴西人口 在城市地区消灭血吸虫病可能是一个比从一个城市地区 农村地区。城市疫源地一般由较轻的感染组成，因此更接近于从消除开始。 指向。此外，城市卫生设施总体上要好一些。最后，在感染的城市更有可能消除局部感染。 存在于小的“岛屿”中。在一例中发现了曼氏葡萄球菌传播和人类感染的活跃部位 巴西巴伊亚州萨尔瓦多的一个社区，这座拥有300万人口的城市，在其他社区感染了蜗牛。分析 人口结构的变化表明，与农村地区相比，人口的空间碎片化程度更大。感染情况如何？ 以及人类、寄生虫和蜗牛种群如何随着时间的变化而变化 对如何消除传播的影响。这项提案将收集纵向人口统计数据， 巴西城市血吸虫病传播疫源地的寄生虫遗传、软化和环境数据。 将每年对血吸虫病流行情况进行人口统计调查的两个社区 信息和血吸虫粪便虫卵，那些感染者将得到治疗。当地的水接触地点也将 每月调查钉螺感染情况、人类粪便污染情况和气候条件。寄生虫 将对种群进行遗传特征和跟踪，以及人类的空间和纵向分布 将对粪便污染和蜗牛种群进行评估，并与风险相关。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引导管理战略走向根除。

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.