title: Human fecal and pathogen exposure pathways in rural Indian villages and the effect of increased latrine coverage.
abstract: Efforts to eradicate open defecation and improve sanitation access are unlikely to achieve health benefits unless interventions reduce microbial exposures. This study assessed human fecal contamination and pathogen exposures in rural India, and the effect of increased sanitation coverage on contamination and exposure rates. In a cross-sectional study of 60 villages of a cluster-randomized controlled sanitation trial in Odisha, India, human and domestic animal fecal contamination was measured in community tubewells and ponds (n = 301) and via exposure pathways in homes (n = 354), using Bacteroidales microbial source tracking fecal markers validated in India. Community water sources were further tested for diarrheal pathogens (rotavirus, adenovirus and Vibrio cholerae by quantitative PCR; pathogenic Escherichia coli by multiplex PCR; Cryptosporidium and Giardia by immunomagnetic separation and direct fluorescent antibody microscopy). Exposure pathways in intervention and control villages were compared and relationships with child diarrhea examined. Human fecal markers were rarely detected in tubewells (2.4%, 95%CI: 0.3-4.5%) and ponds (5.6%, 95%CI: 0.8-10.3%), compared to homes (35.4%, 95%CI: 30.4-40.4%). In tubewells, V. cholerae was the most frequently detected pathogen (19.8%, 95%CI: 14.4-25.2%), followed by Giardia (14.8%, 95%CI: 10.0-19.7%). In ponds, Giardia was most often detected (74.5%, 95%CI: 65.7-83.3%), followed by pathogenic E. coli (48.1%, 95%CI: 34.8-61.5%) and rotavirus (44.4%, 95%CI: 34.2-54.7%). At village-level, prevalence of fecal pathogen detection in community drinking water sources was associated with elevated prevalence of child diarrhea within 6 weeks of testing (RR 2.13, 95%CI: 1.25-3.63) while within homes, higher levels of human and animal fecal marker detection were associated with increased risks of subsequent child diarrhea (P = 0.044 and 0.013, respectively). There was no evidence that the intervention, which increased functional latrine coverage and use by 27 percentage points, reduced human fecal contamination in any tested pathway, nor the prevalence of pathogens in water sources. In conclusion, the study demonstrates that (1) improved sanitation alone may be insufficient and further interventions needed in the domestic domain to reduce widespread human and animal fecal contamination observed in homes, (2) pathogens detected in tubewells indicate these sources are microbiologically unsafe for drinking and were associated with child diarrhea, (3) domestic use of ponds heavily contaminated with multiple pathogens presents an under-recognized health risk, and (4) a 27 percentage point increase in improved sanitation access at village-level did not reduce detectable human fecal and pathogen contamination in this setting.
authors.affiliation: Dept. of Civil and Environmental Engineering, University of California, Davis, One Shields Avenue, Davis, CA, USA.
authors.forename: Mitsunori
authors.initials: M
authors.lastname: Odagiri
authors.affiliation: Dept. of Civil and Environmental Engineering, University of California, Davis, One Shields Avenue, Davis, CA, USA.
authors.forename: Alexander
authors.initials: A
authors.lastname: Schriewer
authors.affiliation: Dept. of Veterinary Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA, USA.
authors.forename: Miles E
authors.initials: ME
authors.lastname: Daniels
authors.affiliation: Dept. of Civil and Environmental Engineering, University of California, Davis, One Shields Avenue, Davis, CA, USA; Singapore Centre for Environmental Life Sciences Engineering (SCELSE), Nanyang Technological University, 60 Nanyang Drive, Singapore; School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore.
authors.forename: Stefan
authors.initials: S
authors.lastname: Wuertz
authors.affiliation: Dept. of Veterinary Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA, USA.
authors.forename: Woutrina A
authors.initials: WA
authors.lastname: Smith
authors.affiliation: Dept. of Environmental Health, Rollins School of Public Health, Emory University, Atlanta, GA, USA; Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK.
authors.forename: Thomas
authors.initials: T
authors.lastname: Clasen
authors.affiliation: Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK.
authors.forename: Wolf-Peter
authors.initials: WP
authors.lastname: Schmidt
authors.affiliation: Dept. of Civil and Environmental Engineering, University of California, Davis, One Shields Avenue, Davis, CA, USA.
authors.forename: Yujie
authors.initials: Y
authors.lastname: Jin
authors.affiliation: Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK.
authors.forename: Belen
authors.initials: B
authors.lastname: Torondel
authors.affiliation: Asian Institute of Public Health, Bhubaneswar, Odisha, India.
authors.forename: Pravas R
authors.initials: PR
authors.lastname: Misra
authors.affiliation: Dept. of Epidemiology, Center for Global Health and Development, College of Public Health, University of Nebraska Medical Center, Omaha, NE, USA; Dept. of Pediatrics, Center for Global Health and Development, College of Public Health, University of Nebraska Medical Center, Omaha, NE, USA.
authors.forename: Pinaki
authors.initials: P
authors.lastname: Panigrahi
authors.affiliation: Dept. of Civil and Environmental Engineering, University of California, Davis, One Shields Avenue, Davis, CA, USA; Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK. Electronic address: mwjenkins@ucdavis.edu.
authors.forename: Marion W
authors.initials: MW
authors.lastname: Jenkins
mesh_terms: D000818:Animals; D002648:Child; D003430:Cross-Sectional Studies; D003967:Diarrhea / Q000517:prevention & control*; D004926:Escherichia coli; D005243:Feces / Q000382:microbiology; D006801:Humans; D011634:Public Health; D012306:Risk; D012499:Sanitation; D014038:Toilet Facilities; D014881:Water Supply
keywords: Bacteroidales; Child diarrhea prevalence; Drinking water contamination; Hand contamination; Improved sanitation; Microbial source tracking