Date Published: March 22, 2018
Publisher: The American Society of Tropical Medicine and Hygiene
Author(s): Tala Navab-Daneshmand, Max N. D. Friedrich, Marja Gächter, Maria Camila Montealegre, Linn S. Mlambo, Tamuka Nhiwatiwa, Hans-Joachim Mosler, Timothy R. Julian.
Escherichia coli pathotypes (i.e., enteropathogenic and enterotoxigenic) have been identified among the pathogens most responsible for moderate-to-severe diarrhea in low- and middle-income countries (LMICs). Pathogenic E. coli are transmitted from infected human or animal feces to new susceptible hosts via environmental reservoirs such as hands, water, and soil. Commensal E. coli, which includes nonpathogenic E. coli strains, are widely used as fecal bacteria indicator, with their presence associated with increased likelihood of enteric pathogens and/or diarrheal disease. In this study, we investigated E. coli contamination in environmental reservoirs within households (N = 142) in high-population density communities of Harare, Zimbabwe. We further assessed the interconnectedness of the environmental compartments by investigating associations between, and household-level risk factors for, E. coli contamination. From the data we collected, the source and risk factors for E. coli contamination are not readily apparent. One notable exception is the presence of running tap water on the household plot, which is associated with significantly less E. coli contamination of drinking water, handwashing water, and hands after handwashing. In addition, E. coli levels on hands after washing are significantly associated with handwashing water contamination, hand contamination before washing, and diarrhea incidence. Finally, we observed that animal ownership increases E. coli contamination in soil, and E. coli in soil are correlated with contamination on hands before washing. This study highlights the complexity of E. coli contamination in household environments within LMICs. More, larger, studies are needed to better identify sources and exposure pathways of E. coli—and enteric pathogens generally—to identify effective interventions.
Gastrointestinal diseases cause an estimated 5–700,000 deaths in children aged less than 5 years annually.1 Recent studies have identified a subset of enteric pathogens (enterotoxigenic and enteropathogenic Escherichia coli, Shigella spp., rotavirus, calicivirus, and Cryptosporidium spp.) as the leading causes of moderate-to-severe diarrhea and/or mortality in low- and middle-income countries (LMICs).2,3 These pathogens are likely transmitted from human or animal feces to susceptible hosts through interactions with food and environmental compartments (i.e., flies, hands, soil, surfaces, and water).3–5 Fecal indicator bacteria, including E. coli, are widely used as indicators to study the sources and fate of fecal contamination in the environment. The presence of E. coli in drinking water, for example, is associated with increased risk of both enteric pathogens and diarrheal disease, generally.6–8 Research to date largely focuses on the role of food and water in the transmission of enteric bacteria, but recent evidence has highlighted the potential importance of other compartments including hands and soil.9–13
In households with young children in peri-urban Harare, Zimbabwe, we observed extensive E. coli contamination of environmental compartments, including drinking and handwashing water, soil, and hands before and after handwashing. The source and risk factors for E. coli contamination are not readily apparent from the data we collected on either household-level WASH risk factors or E. coli contamination of other compartments. One notable exception, however, is the presence of running tap water which is associated with significantly less E. coli contamination of drinking water, handwashing water, and hands after handwashing (but not soil nor hands before handwashing).