Spatiotemporal Distribution of Visceral Leishmaniasis with Consideration of Environmental Risk Factors, Minas Gerais, Brazil, 2012-2018 Open Access

Abstract

Visceral leishmaniasis (VL) is endemic in Brazil, representing 97% of all VL cases in the Americas. Previous studies have described the distribution of visceral leishmaniasis cases in Minas Gerais (MG), Brazil, indicating spatial heterogeneity at a mesoregion level. Environmental factors such as urbanization, rainfall, vegetation, and temperature, have been found to be associated with VL, but data are limited for MG. This study describes the incidence of VL in MG, evaluates environmental factors impacting VL incidence in the state, and reviews areas of high risk and clustering of the disease. A spatiotemporal ecological study utilizing confirmed cases of VL by municipality through the Brazilian Notifiable Disease Information System (SINAN) was conducted from January 2012 through December 2018. Maps of VL cumulative and annual incidence were created to evaluate the spatial heterogeneity of disease across the state. Multivariate negative binomial regression models were developed for the overall time period, as well as annually to evaluate the association between minimum temperature, maximum temperature, total precipitation, urban residence, and normalized vegetation, and VL incidence. Local indicator of spatial autocorrelation (LISA) and Kulldorff spatial scan statistics were conducted to evaluate clustering. Over the study period 3,501 cases of VL were reported across Minas Gerais, for a cumulative incidence of 16.5 cases per 100,000 persons. The average annual incidence rate in MG was 2.1 cases per 100,000 persons. Maximum temperature and rainfall displayed significant association with VL incidence in MG in the overall model. Annual models differed with temperature, rainfall, and urbanicity being significant across different years. Significant clustering of VL was observed in northern MG. This study offers insight into the distribution of VL in Minas Gerais, how environmental factors are impacting the disease in the state, and where clustering is most likely occurring. These results help offer guidance on prevention and control efforts for VL in Minas Gerais, Brazil.

Table of Contents

LITERATURE REVIEW 1

MANUSCRIPT 10

ABSTRACT 10

INTRODUCTION 12

METHODS 14

RESULTS 18

DISCUSSION 21

REFERENCES 28

TABLES 39

Table 1. Descriptive Characteristics of Visceral Leishmaniasis Cases in Minas Gerais, Brazil, 2012-2018. 39

Table 2. Descriptive Characteristics of Environmental Factors Considered in Minas Gerais, Brazil, 2012-2018. 40

Table 3. Overall Multivariate Analysis of Association between Environmental Risk Factors and Visceral Leishmaniasis Incidence in Minas Gerais, Brazil, 2012-2018. 41

Table 4. Annual Multivariate Analysis of Association between Environmental Risk Factors and Visceral Leishmaniasis Incidence in Minas Gerais, Brazil, 2012-2018. 42

FIGURES 44 

Figure 1. Map of Minas Gerais, Brazil 44

Figure 2. Distribution of Visceral Leishmaniasis Cases by Resident Municipality, Minas Gerais, Brazil, 2012-2018. 45

Figure 3. Cumulative Incidence of Visceral Leishmaniasis by Resident Municipality in Minas Gerais, Brazil, 2012-2018. 46

Figure 4. Annual Visceral Leishmaniasis Incidence by Resident Municipality in Minas Gerais, Brazil, 2012-2018. 47

Figure 5. Municipalities Considered Signficiant High Risk Areas for Visceral Leishmaniasis in Minas Gerais, Brazil, 2012-2018. 48

Figure 6. Municipalities Considered Signficiant High Risk Areas for Visceral Leishmaniasis in Minas Gerais, Brazil, 2013 & 2017. 49

Figure 7. Local Spatial Autocorrelation of Visceral Leishmaniasis Incidence, Minas Gerais, Brazil, 2012-2018. 50

Figure 8. Local Spatial Autocorrelation of Visceral Leishmaniasis Incidence, Minas Gerais, Brazil, 2013 & 2017. 51

Figure 9. Locations of Most Likely Visceral Leishmaniasis Clustering, Minas Gerais, Brazil, 2012-2018. 52

CONCLUSIONS 53

SUMMARY 53

PUBLIC HEALTH IMPLICATIONS 53

FUTURE DIRECTIONS 54

APPENDIX 56

Figure S1. Distribution of Visceral Leishmaniasis Cases by Reporting Municipality, Minas Gerais, Brazil, 2012-2018. 56

Figure S2. Cumulative Incidence of Visceral Leishmaniasis by Reporting Municipality in Minas Gerais, Brazil, 2012-2018. 57

Figure S3. Annual Visceral Leishmaniasis Incidence by Reporting Municipality in Minas Gerais, Brazil, 2012-2018. 58

Figure S4. Aspatially Smoothed Bayes Annual Visceral Leishmaniasis Incidence by Resident Municipality in Minas Gerais, Brazil, 2012-2018. 59

Figure S5. Spatially Smoothed Bayes Annual Visceral Leishmaniasis Incidence by Resident Municipality in Minas Gerais, Brazil, 2012-2018. 60

About this Master's Thesis

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School	Rollins School of Public Health
Department	Epidemiology
Subfield / Discipline	Epidemiology - MPH & MSPH
Degree	M.P.H.
Submission	Master's Thesis
Language	English
Research Field	Environmental Sciences Health Sciences, Public Health Health Sciences, Epidemiology
Keyword	Leishmaniasis Brazil Environment
Committee Chair / Thesis Advisor	Kitron, Uriel, Emory University
Committee Members	Clennon, Julie, Emory University Fairley, Jessica, Emory University

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