Effect of WASH interventions on population resilience to climate-driven enteric pathogen transmission along a gradient of socio-economic position

Background: Most of rural Bangladesh is situated in the Ganges-Brahmaputra-Meghna river basin which is home to over 618 million people and represents one of the most climate-sensitive populations in the world. Living in the basin exposes the population to extreme climates such as heavy precipitation during annual monsoons. The country also has one of the highest diarrhea prevalence rates among children under 5. The enteric pathogens that cause diarrhea are impacted differently by seasonal and long-term changes in precipitation or temperature depending on their biology and modes of transmission. Water, sanitation and handwashing (WASH) interventions have been crucial in preventing and reducing enteric pathogens transmission. However, whether WASH interventions mitigate climate-driven transmission for several enteric pathogens and whether these effects are equitable along a gradient of socio-economic position is still unknown. Aims: The principal aim of this study is to measure the effect of an integrated WASH intervention to prevent climatically driven, seasonal increases in enteric pathogen seroconversion among rural Bangladeshi children and examine whether effects vary along a wealth gradient. We hypothesize that the protective benefit of the WASH intervention on enteric pathogen seroconversion will be larger among children who were exposed to more months of monsoon season, defined as the period of seasonally elevated precipitation. We also hypothesize that the WASH intervention will reduce enteric pathogen seroconversion more among children born into poorer households than among children born into more affluent households. We further hypothesize that the protective benefits of improved WASH to reduce enteric pathogen seroconversion during the monsoon season will be largest in poorer households and that we can use geospatial methods to transport effects from the trial to larger areas, and thus identify populations in rural Bangladesh that would benefit the most from similar WASH interventions. Methods: To test our hypotheses, we will use the serology of 10 enteric pathogens collected from the entire birth cohort of the cluster-randomized trial in our ongoing grant (R01AI166671) after 2 years of intervention when the children were around 24 months old (n=3,831), and from an intensive substudy that collected samples at ages 6, 12, and 24 months from ~1,500 children. We will measure the effect of an integrated WASH intervention on enteric pathogen seroconversion by the number of months exposed to monsoon season and along a gradient of socio-economic position using generalized additive models. We will transport pathogen-specific effects estimated within the trial to broader populations throughout rural Bangladesh which will enable us to identify vulnerable regions that would benefit most from the integrated WASH interventions. This study will represent a generalizable example of extending large-scale randomized controlled trials in climate-sensitive populations with new geospatial data to answer key questions related to climate change and health.