Environmental change and diarrheal disease: A natural experiment

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DESCRIPTION (provided by applicant): Diarrheal diseases are predictable outcomes when fecal-oral pathogens meet human poverty and-dislocation. Are diarrheal diseases sensitive indicators of change in socioeconomic level, resource availability, and human social contacts? Processes like these are extremely difficult to study in a controlled fashion. The construction of a new road in coastal Ecuador provides a valuable natural experiment for this purpose. This road will link some previously remote villages to local, regional, and national networks of goods, services, and people, creating new connections among them. We hypothesize that: (1) the level and type of connections between villages are correlated with infection of enteric pathogens; and (2) the changing social connections, new resources, and sanitary and hygienic behaviors of individuals within villages are correlated with infection of enteric pathogens. These hypotheses use the village as their unit of analysis. When estimating the contribution of various exposure risks to disease incidence, it is also important to explore the implications of interdependence between these pathways. This is the third aim of our study: analyzing the joint effects of changes in these contact patterns using disease transmission models. Using a quasi-experimental design, twenty villages will be followed for 4 years, selected so that a rural-urban continuum is fully represented. This continuum will be measured by several factors that relate a given village to Borbon, the town located at the confluence of two rivers that support the villages within the region. Data will be collected at three levels. First, health promoters who live in the villages under study will implement an active surveillance program. They will administer a new survey tool to measure the incidence of all the diarrheal illnesses and monitor both proximal and distal determinants of disease, in a given village. Second, a biannual visit to each community will be conducted by our field team, which has recently completed a cross sectional feasibility study in these villages. Each visit will last two weeks. In these visits, stool samples will be collected from all symptomatic individuals and a random selection of controls. In addition, during these visits, survey tools will be used to collect information on water-use behavior sanitation, hygiene, food consumption patterns, and travel and migration. Third, semi-annual visits to each village will be undertaken by the local Ecuadorian anthropologist. These visits will include open-ended interviews as well as additional questions about social network formation and change. The visits will also allow village development and road.