Road development as a driver for microbial transmission in northern coastal Ecuador

Transcription

1 Road development as a driver for microbial transmission in northern coastal Ecuador The influence of global environmental change on infectious disease dynamics Institute of Medicine Forum on Microbial Threat September 23, 2013 Joseph Eisenberg, PhD University of Michigan

2 How New Roads Affect the Transmission of Enteric Pathogens Both ecological and social drivers of transmission are influenced by roads. Past studies focused on Roads and STDs, driven largely by social processes Roads and vectorborne disease s, driven largely by ecological processes Enteric pathogens affected by both types of drivers

3 Roads: What Do They Bring? Primary Roads Lead to secondary road construction

4 Roads Facilitate Movement

5 Roads Facilitate Changes in Population Structure

6 Roads Cause Environmental Change Ecologic Social

7 Public Health Burden Diarrheal diseases major cause of childhood mortality One billion lacking adequate water and sanitation Evolution and spread of antibiotic resistance threatens human health Rural northern Ecuador particularly vulnerable Changing social structures barrier to good water, sanitation and hygiene Human and animal use of antibiotics promoted by road

8 Pathways of Enteric Pathogen Transmission: Multiple pathogens, hosts, and environmental niches result in a complex transmission system Pathogens Viruses, bacteria, protozoa Hosts/Reservoirs Animals, humans, environment Routes Foodborne, personperson, Waterborne, Animal-person

9 Pathways of Enteric Pathogen Transmission (Eisenberg et al, 2007)

10 Evolution and Spread of Antibiotic Resistance Occurs Over Multiple Scales Individual level Antibiotic use for medical reasons Community level Spread through water, sanitation and hygiene pathways Introduction through migration Environmental exposures (spread through water, soil) Antibiotic use for agricultural reasons Natural sources Regional level Spread from village to village by either human movement or water transport All scales are potentially affected by road proximity Need to move beyond the individual scale to an ecologic scale of analysis

11 System of Antibiotic Evolution and Spread at Village-level OUTSIDE FOOD SOURCES F F FOOD CROPS HUMAN ANTIBIOTIC USE F O ANIMAL ANTIBIOTIC USE SOIL Natural Occurrence E HUMAN WASTE E ANIMAL WASTE TRANSMISSION PATHWAYS OF Ab RESISTANCE: F = food E = environment O = occupational exposure RIVER (drinking water source)

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13 Study Site Coastal rainforest Afro-Ecuadorian and Chachi Indians 300-year history of living independently Riverine transport system adequate for gold mining, Rubber tapping, and tagua Road system needed for logging and oil palm plantation 1996 begin road construction linking coast and Andes Connects villages along three rivers

14 Study Design Objective To understand how pathogen transmission is impacted by household, community and regional-level factors Design Villages visited on rotational basis 15-day visits Collect all cases during 15 days Community controls Pathogens of interest Rotavirus, E. coli, Giardia Antibiotic resistant bacteria Humans and chickens Dengue

15 Comparison of Infection Prevalence Overall infection prevalence (including subclinical cases) Estimates adjusted for age, village population size, sanitation level, and rain The remoteness metric compares the farthest village with the closest E. coli Rotavirus Giardia Diarrhea OR (95% CI) OR (95% CI) OR (95% CI) OR (95% CI) Far Medium 3.0 (0.8, 11.9) 1.3 (0.5, 3.2) 1.2 (0.7, 2.0) 1.8 (1.1, 3.0) Close 3.9 (1.1, 13.6) 4.1 (2.0, 8.4) 1.6 (1.0, 2.4) 1.8 (1.2, 2.6) Remoteness 8.4 (1.6, 43.5) 4.0 (1.3, 12.1) 1.9 (1.3, 2.7) 2.7 (1.5, 4.8)

16 Causal Model of Transmission Potential Differences in spatial trends among marker pathogens Pathogens with higher Ro less impacted by remoteness Ro function of shedding rates, environmental persistence, and infectious inoculum Shedding Environmental persistence Infectious inoculum (ID 50 ) Giardia Long-term Asym & Sym Rotavirus High ( ) Long (but depends on temp) Long 10 E coli Lower (10 8 ) Shorter

17 Regional Patterns of Antibiotic Resistance Comparing prevalence of sulfamethoxazole and ampicillin resistance by remoteness Community-level prevalence Sulfamethoxazole and Ampicillin Resistance Remoteness OR (95% CI) Far 1.0 Medium 1.1 (0.6, 1.8) Close 1.8 (1.3, 2.3) Multivariate model controlling for age, population size, and Ab use Adjusting for correlation within the village

18 Possible Explanations of Spatial Patterns Hypotheses Antibiotic use? Spread of antibiotics, antibiotic resistant bacteria, gene-gene transfer? Reintroduction of antibiotic resistant bacteria?

19 Village Level Transmission Analysis Transmission rates (b and h) Use E. coli prevalence in road vs. remote villages (PNAS 2006) Assume SIS model of transmission Antibiotic use rates (r) Survey data (20% random sample of households) h Y l (ingestion rate) Exposed r b Z Amplified Colonized - - Transmission r: Antibiotic use rate

20 Explaining Patterns of E. coli Resistance in Communities Comparing road and remote villages Antibiotic use determines the importance of introduction of resistance vs. transmission Low antibiotic use High antibiotic use

21 Potential chain of causal effects explaining our findings Social networks conduits of transmission (contacts) or protective (relationships)? Disease spreads more slowly to and in remote villages Though reduced contact; greater density of social ties facilitates spread collective protective practices Road Proximity Remoteness Migration In and Out Contact outside village # visitors Short-term travel Social Cohesion Size of social network Infrastructure Sanitation Hygiene Reintroduction of pathogenic strains Diarrhea Pathogen infection

22 Ecological Perspective: Social Networks Heterogeneous social landscape across villages Networks for similar size villages Remote village Close village Isolates not shown

23 Ecological Perspective: Social Networks Risks and protective effects are mediated through a number of social processes OR = 0.49 (0.29, 0.84) Within-village Infectious contacts + OR = 0.89 (0.81, 0.98)

24 Predicted diarrheal prevalence Ecological Perspective: Social Networks There are independent geographic and social components of risk 12 Predicted diarrheal prevalence per 100 persons per 2-week cycle Lowest Highest estimate=3.12 estimate=0.95 Avg. distance from households Spatial index RR RR = (1.1, (1.1, 10) 10.0) Lowest Highest estimate=3.93 estimate=1.15 Contact network (degree) RR=3.4 Contact (1.1, degree 10.1) RR = 3.4 (1.1, 10.1) Lowest Highest estimate=4.66 estimate=0.95 Food network (degree) Food degree RR=4.9 (1.1, 21.9) RR = 4.9 (1.1, 21.9)

25 Ecological Perspective: Social Networks Mechanisms of transmission Geographic component risk factors Population density Contaminated environment Social component risk and protective factors Person to person transmission Social ties

26 An Ecological Perspective The presence of road causes environmental changes (social and ecological) These changes occur differentially across the landscape of villages Affects social structure Spread of microorganisms differentially through water sanitation and hygiene pathways Affects movement and migration patterns at multiple scales Affects climate and hydrological processes Remoteness relative to Borbón Close Medium Far Regional patterns of environmental change will vary over time.

27 Acknowledgments Ecuador William Cevallos (Project director) Gabriel Trueba (PI: Microbiologist) Diana Lopez (Microbiologist) Eugenia Meja (Microbiologist) Maria Ines Baquero (Microbiologist) Andres Acevedo (Field anthropologist) Vilma Requene (Field assistant) Mariuxi Ayovi (Field assistant) Deni Tenorio (Field assistant) Mauricio Ayovi (Field assistant) Maritza Renteria (Field assistant) Jose Ortiz (Transportation coordinator) Emel Bustamante (Data entry) United States James Trostle Betsy Foxman, Carl Marrs, Lixin Zhang, Karen Levy James Fuller Ian Spicknell, Jason Goldstick, Jon Zelner, Robert Wood Health Promoters Deni Orobio, Pastor Mercado, Cecilia Mercado, Carmen Nazareno, Ludis Castillo, Mirtha Campaz, Estela Arroyo, Ramona Sabando, Maria Ayovi, Blanca Vega, Jorge Peralta, Santos Mina, Amelia Preciado, Marco B., Ereccni Cuero, Julio Valdez, Lucrecio Palacio, Heroina Arboleda, Juliana Mina, Adalin Valencia, Mariuxci C., Dominga A., Maria Arroyo, Gonzolo M., Gabriel Ayovi, Maria Corozo