Predictors of Enteric Pathogens in the Domestic Environment from Human and Animal Sources in Rural Bangladesh.

Erica R Fuhrmeister ,Alan Hubbard ,Leanne Unicomb ,Laura H Kwong ,Ayşe Ercümen ,Debashis Sen ,Sharmin Islam ,Sara Brown ,Stephen P Luby ,Mahfuza Islam ,Alexandria B Boehm ,Mahbubur Rahman ,Kaitlyn M Jeanis ,Mohammad Murshid Alam ,John M Colford ,Mir Himayet Kabir ,Amy J Pickering ,Benjamin F Arnold ,Mahaa Ahmed ,Kara L Nelson

doi:10.1021/acs.est.8b07192

Abstract

Fecal indicator organisms are measured to indicate the presence of fecal pollution, yet the association between indicators and pathogens varies by context. The goal of this study was to empirically evaluate the relationships between indicator Escherichia coli, microbial source tracking markers, select enteric pathogen genes, and potential sources of enteric pathogens in 600 rural Bangladeshi households. We measured indicators and pathogen genes in stored drinking water, soil, and on mother and child hands. Additionally, survey and observational data on sanitation and domestic hygiene practices were collected. Log10 concentrations of indicator E. coli were positively associated with the prevalence of pathogenic E. coli genes in all sample types. Given the current need to rely on indicators to assess fecal contamination in the field, it is significant that in this study context indicator E. coli concentrations, measured by IDEXX Colilert-18, provided quantitative information on the presence of pathogenic E. coli in different sample types. There were no significant associations between the human fecal marker (HumM2) and human-specific pathogens in any environmental sample type. There was an increase in the prevalence of Giardia lamblia genes, any E. coli virulence gene, and the specific E. coli virulence genes stx1/2 with every log10 increase in the concentration of the animal fecal marker (BacCow) on mothers’ hands. Thus, domestic animals were important contributors to enteric pathogens in these households.

Highlights

In low- and middle-income countries, diarrheal illness is a leading cause of morbidity and mortality.[1]
Pathogens associated with both human and animal feces include Cryptosporidium, Giardia lamblia, EPEC, STEC, and ETEC.[15−17] Humans serve as a reservoir of typical EPEC, while animals such as pigs and chickens can serve as reservoirs of atypical EPEC.[17,18]
We investigated threshold trends in stored water associated with the WHO water quality guidelines by evaluating PPV, NPV, sensitivity, and specificity of pathogen presence and indicator E. coli concentrations above cutoff values

Summary

Introduction

In low- and middle-income countries, diarrheal illness is a leading cause of morbidity and mortality.[1] In Bangladesh, 6% of the 129 000 deaths in children under five in 2013 were attributed to diarrheal diseases.[2] Diarrheal illness results from exposure to fecal pathogens which can be transmitted from feces to a new human host through a variety of environmental pathways, including fingers, fields, flies, fluids, and food, described in the F-diagram.[3] Recent additions to the F-diagram stress the importance of animal hosts by expanding fecal sources to include feces from livestock, free-roaming animals, and synanthropic rodents.[4] While it is well-known that enteric pathogens are transmitted through these pathways, few studies have measured pathogens to characterize exposure from different animal reservoirs. There is a high potential for zoonotic enteric disease transmission in low- and middle- income countries where animal husbandry is a primary source of income.[5] For example, in Bangladesh raising livestock such as cows, goats, and chickens results in animals roaming freely within the home environment.[6] Close proximity to domesticated animals can lead to human exposure to livestock feces. Of the five most common etiological agents of moderate to severe diarrhea in children 0−11 months in Received: December 21, 2018 Revised: July 24, 2019 Accepted: July 29, 2019 Published: July 29, 2019

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Results