Rethinking Indicators of Microbial Drinking Water Quality for Health Studies in Tropical Developing Countries: Case Study in Northern Coastal Ecuador

• Type of Material: Article
• Authors: Karen Levy, Emory University; Kara L. Nelson, University of California Berkeley; Alan Hubbard, University of California Berkeley; Joseph N. S. Eisenberg, University of Michigan
• Language: English
• Date: 2012-03-01
• Publisher: American Society of Tropical Medicine and Hygiene
• Publication Version: Final Published Version
• Copyright Statement: ©The American Society of Tropical Medicine and Hygiene
• Final Published Version (URL): http://www.ajtmh.org/content/86/3/499
• Title of Journal or Parent Work: American Journal of Tropical Medicine and Hygiene
• ISSN: 0002-9637
• Volume: 86
• Issue: 3
• Start Page: 499
• End Page: 507
• Grant/Funding Information: his study was supported by grants from the National Institute of Allergy and Infectious Diseases (RO1AI050038), the University of California Pacific Rim Research Program, and the University of California Center for Occupational and Environmental Health.
• Research Categories: Health Sciences, Epidemiology; Health Sciences, Public Health

Abstract

To address the problem of the health impacts of unsafe drinking water, methods are needed to assess microbiologic contamination in water. However, indicators of water quality have provided mixed results. We evaluate five assays (three for Escherichia coli and one each for enterococci and somatic coliphage) of microbial contamination in villages in rural Ecuador that rely mostly on untreated drinking water. Only membrane filtration for E. coli using mI agar detected a significant association with household diarrheal disease outcome (odds ratio = 1.29, 95% confidence interval = 1.02–1.65 in household containers and odds ratio = 1.18, 95% confidence interval = 1.02–1.37) in source samples. Our analysis and other published research points to the need for further consideration of study design factors, such as sample size and variability in measurements, when using indicator organisms, especially when relating water quality exposure to health outcomes. Although indicator organisms are used extensively in health studies, we argue that their use requires a full understanding of their purposes and limitations.