Impact of Human Movement along an Urban-Rural Gradient on Diarrheal Risk and Pathogen-Specific Diarrhea: Case Control Study in Ecuador, 2014 - 2015 Open Access

Abstract

Diarrheal diseases are a common cause of morbidity and mortality, affecting millions of people worldwide. Diarrhea-related deaths disproportionally affect young children and low-income nations. Diarrheagenic E. coli (DEC) infections in particular are associated with diarrheal presence globally, including throughout Latin America and Ecuador. Despite reductions seen in diarrheal deaths, Ecuador still maintains a high burden of disease. Thus there is a need to further the understanding of diarrheal risk and pathogen-specific diarrhea, and to understand how the burden of specific pathogens varies between urban and rural locations. Within-country human movement between urban and rural locations has the potential to increase disease transmission and should be included in the assessment of diarrheal risk.

The EcoZur study is a case-control study of diarrheal diseases along an urban-rural gradient in Ecuador. At each study site, ~100 diarrheal cases were recruited from Ministry of Health clinics and age-matched to ~100 non-diarrheal controls from the same facility. Demographics, medical history, WASH practices, animal contacts, and recent travel history information was collected on all participants using an electronic survey. Additionally, stool samples were collected within 24 hours from all participants for enteric pathogen testing.

The study found that the urban-rural gradient accurately represented a gradient of socioeconomic status and access to clean and safe water/sanitation. Treatment of drinking water was significantly protective against diarrhea in urban sites (Quito aOR: 0.58, 95% CI: 0.34, 0.97; Esmeraldas aOR: 0.41, 95% CI: 0.22, 0.75) and improved sanitation practices were protective against diarrhea in rural sites, specifically in the town of Borbón (aOR: 0.28; 95% CI: 0.09, 0.73). Travel in the past year was significantly associated with diarrhea among all participants (aOR: 1.36; 95% CI: 1.05, 1.77), and specifically among participants from Esmeraldas (aOR: 2.53; 95% CI: 1.36, 4.81), with travel to Quito being a greater risk for not only diarrheal disease, but also DEC infections in general. Urban sites were also found to be associated with a higher proportion of DAEC infection compared to rural sites that had higher EPEC-a and ETEC infections. Interestingly, DAEC infections were significantly associated with diarrhea only in urban centers and ETEC infections were significantly associated with diarrhea in the rural center of Borbón only. This study highlights the differential etiologic agents of diarrhea in urban versus rural areas of one country, and identifies travel as a risk factor for diarrhea and DEC, in addition to the known water and sanitation risk factors.

Table of Contents

Table of Contents

I. BACKGROUND.............................................................................................................. 1

Global Diarrheal Disease Burden........................................................................................................................... 1

Pathogen-Specific Diarrheal Disease................................................................................................................... 2

Diarrheal Diseases in Latin America and Ecuador..................................................................................... 4

Water, Sanitation and Hygiene (WASH) Risk Factors for Diarrheal Diseases..................... 5

Travel as a Risk Factor for Diarrheal Diseases.......................................................................................... 6

Study Significance................................................................................................................................................................ 7

II. METHODS...................................................................................................................... 9

Study Design.............................................................................................................................................................................. 9

Study Participants............................................................................................................................................................ 10

Data Collection................................................................................................................................................................... 11

Pathogen Identification................................................................................................................................................ 12

Data Cleaning........................................................................................................................................................................ 13

Bivariate Analysis............................................................................................................................................................. 13

Multivariate Analysis.................................................................................................................................................... 15

III. RESULTS.................................................................................................................... 18

Participant Characteristics..................................................................................................................................... 18

Bivariate Analysis............................................................................................................................................................. 19

Risk Factors for Diarrheal Disease...................................................................................................................... 19

Pathogen-Specific Risk Factors for Diarrheal Disease.......................................................................... 25

Multivariate Analysis.................................................................................................................................................... 32

Association between enteric infections and diarrheal diseases.................................................... 34

IV. DISCUSSION.............................................................................................................. 36

Risk Factors for Diarrheal Diseases................................................................................................................. 36

Risk Factors for Pathogen-Specific Diarrhea............................................................................................ 38

Pathogen-Specific Associations with Diarrheal Disease.................................................................... 40

Strengths and Weaknesses........................................................................................................................................... 40

Limitations............................................................................................................................................................................... 41

Future Direction................................................................................................................................................................. 41

V. REFERENCES.............................................................................................................. 42

VI. APPENDIX. Supplemental Tables and Figures....................................... 45

About this Master's Thesis

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School	Rollins School of Public Health
Department	Epidemiology
Subfield / Discipline	Global Epidemiology - MPH & MSPH
Degree	MPH
Submission	Master's Thesis
Language	English
Research Field	Health Sciences, Public Health Environmental Health Health Sciences, Epidemiology
Keyword	travel enteroaggregative E. coli sanitation urban-rural gradient diarrheal diseases Ecuador drinking water enteroinvasive E. coli enteropathogenic E. coli enterotoxigenic E. coli rotavirus diffusely adhering E. coli
Committee Chair / Thesis Advisor	Levy, Karen, Emory University
Partnering Agencies	University, college or educational institution (other than Emory)

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