Environmental and spatial determinants of enteric pathogen infection in rural Lao People’s Democratic Republic: A cross-sectional study

Though the health risks associated with poor access to water, sanitation, and hygiene (WASH) are well established, recent large-scale WASH trials have found limited impact on enteric disease. The aims of this study were to: 1. estimate the prevalence of enteropathogens among children <5, school-aged children, and adults; 2. model associations between WASH transmission pathways and enteropathogen infections; and 3. quantify clustering of enteropathogen infections at the household- and village-level. We conducted a cross-sectional survey in 50 villages in Saravane Province, Lao People’s Democratic Republic. From 297 households, we collected 891 fecal samples from one child <5, one school-aged child, and one adult living in the same household, and collected survey and observational data on household demographics, WASH access, and animal ownership. Fecal samples were analyzed for 25 enteropathogens using a qRT-PCR assay. We observed near universal infection with at least one enteropathogen (98.3%). Few household or village-level WASH covariates were statistically associated with enteropathogen infection. Concordant household infection was higher than expected under the independence assumption for 14 of the 21 pathogens for which we had sufficient data, indicating strong household correlation for many infections. Median odds ratios (MORs), a measure of cluster-level (e.g. village and household) influence on an individual’s odds of infection, were elevated at the village level, particularly for viruses (MOR: 3.89; 95% confidence interval [CI]: 2.64, 6.69), protozoa (MOR: 2.07; 95% CI: 1.59, 3.10), and soil-transmitted helminths (MOR: 2.46; 95% CI: 1.89, 3.56), indicating strong village-level differences in individuals' odds of enteric infections. WASH access, as hypothesized, is associated with fewer enteroinfections, but WASH access as currently defined does not reveal a measurably protective association with infection for many etiologies. Household- and community-level factors beyond WASH access, such as intra-household pathogen transmission, exposure to animal feces, and contextual factors in the public domain may be important risk factors for enteric infections. TRIAL REGISTRATION: clinicaltrials.gov (NCT02342860).