Effects of sanitation on pathogen transmission and child health in Bangladesh

描述（由申请人提供）：腹泻病在低收入国家的儿童中造成了巨大而持久的疾病负担；死亡率估计将全球5岁以下儿童死亡的10%归因于腹泻。粪口病原体（被认为是腹泻的最重要原因）通过多种复杂的环境介导途径从粪便传播到新的宿主，这些途径相互作用，也受人类行为的影响。防止病原体从粪便传播到环境中的卫生干预措施（例如提供厕所）可以阻断这些传播途径并减轻腹泻病的负担。尽管卫生设施在减少腹泻方面具有潜在的重要性，但迄今为止关于农村环境中儿童胃肠道感染的卫生干预措施的所有研究都采用了非随机设计。此外，很少有研究包括对卫生相关行为的详细监测和对从粪便到儿童疾病的复杂病原体传播途径的微生物学评估。目的：本研究的主要目的是评估改善卫生基础设施和家庭卫生习惯对孟加拉国农村病原体传播途径中粪便污染的影响，并评估这些途径如何调节卫生设施改善对24个月以下儿童腹泻和寄生虫感染的影响。我们假设改善的卫生设施将减少饮用水、家庭土壤和儿童手部的污染；我们还假设这些途径将介导干预引起的腹泻患病率和寄生虫感染的任何减少。方法：我们将通过在WASH Benefits中嵌套微生物和行为测量来验证我们的假设。WASH Benefits是由盖茨基金会资助并由我们的团队领导的一项随机对照试验，目前正在孟加拉国农村进行。从干预后12个月开始，我们将每季度访问试验卫生和控制部门的720个家庭，为期2年。每次来访时，我们将采集管井、池塘、储水、儿童游乐区土壤、管井附近土壤和儿童手上的样本进行粪便指示菌分析。在最后两轮采样中，我们将分析突出的粪便病原体样本，并进行来源跟踪，以区分人类和动物的粪便污染。我们将通过抽查和被动红外传感器测量来监测卫生状况。这些数据将利用现有试验方案中测量的健康结果（腹泻、粪便中的蠕虫和原生动物感染）。我们将使用意向治疗和编译平均因果效应估计来比较研究组之间的粪便污染。我们将通过分析直接和间接影响，估计污染对健康结果的贡献。我们的团队（UC Berkeley, Stanford， ICDDR，B）在由NIH， CDC， DFID， USEPA和盖茨基金会资助的项目中，在孟加拉国和其他低收入国家的水，环境卫生和个人卫生研究方面具有丰富的合作经验。

DESCRIPTION (provided by applicant): Diarrheal illness creates a large and persistent disease burden among children in low-income countries; mortality estimates attribute 10% of global deaths among children < 5 to diarrhea. Fecal-oral pathogens (believed to be the most important causes of diarrhea) are transmitted from feces to new hosts through a variety of complex, environmentally mediated pathways that interact with each other and are also influenced by human behavior. Sanitation interventions that prevent the spread of pathogens from feces into the environment (e.g. provision of latrines) could block these transmission pathways and reduce the burden of diarrheal disease. Despite the potential importance of sanitation in reducing diarrhea, all studies to date of sanitation interventions on child gastrointestinal infections in rural settings have used non-randomized designs. Additionally, few studies have included detailed monitoring of sanitation-related behaviors and microbiological assessment of the complex pathogen transmission pathways that lead from feces to child illness. Aims: The principal aims of this study are to assess the impact of improvements in sanitation infrastructure and household sanitation practices on fecal contamination along pathogen transmission pathways in rural Bangladesh, and to assess how these pathways mediate the impact of sanitation improvements on diarrhea and parasitic infections in children < 24 months old. We hypothesize that improved sanitation will reduce contamination of drinking water, household soil, and children's hands; we also posit that these pathways will mediate any reductions in diarrhea prevalence and parasitic infections caused by the intervention. Methods: We will test our hypotheses by nesting microbiological and behavioral measurements within WASH Benefits, a randomized controlled trial currently underway in rural Bangladesh funded by the Gates Foundation and led by our team. We will visit a total of 720 households from the trial's sanitation and control arms quarterly for 2 years, starting 12 months after intervention. At each visit, we will collect samples from tubewells, ponds, stored water, soil from the child play area, soil near tubewells and from children's hands for analysis of fecal indicator bacteria. During the last two sampling rounds, we will analyze samples for prominent fecal pathogens and perform source tracking to distinguish fecal contamination from humans versus animals. We will monitor sanitation practices through spot checks and passive infrared sensor measurements. These data will leverage the health outcomes measured in the existing trial protocol (diarrhea and helminth and protozoan infections in stool). We will compare fecal contamination between the study arms using intention to treat and complier average causal effect estimators. We will estimate the contribution of contamination to health outcomes through individual pathways by analysis of direct and indirect effects. Our team (UC Berkeley, Stanford, ICDDR,B) has extensive experience collaborating on studies of water, sanitation and hygiene in Bangladesh and other low-income countries on projects funded by the NIH, CDC, DFID, USEPA and the Gates Foundation.