Spatial Distribution of Leprosy and Schistosomiasis and the Role of Coinfection in Leprosy Disease Severity in Minas Gerais, Brazil Open Access

Abstract

Background. Leprosy and schistosomiasis are co-endemic in certain areas of Brazil. It has been demonstrated that leprosy can present in its more infectious and debilitating multibacillary form if the patient concurrently has a helminth infection due to a change in immune response. We hypothesized that this association can be presented spatially and aspatially.

Methods. Aspatial logistic regression was applied to case-control data (n = 126) from a population in Minas Gerais, Brazil to estimate the association between schistosomiasis infection and leprosy infection, as well as multibacillary leprosy. The Kulldorff spatial scan statistic was used to identify clusters of infections and coinfections The Cuzick-Edwards method was used to test for heterogeneity in disease distribution. The local join count statistic was used to identify cluster cores of infections and coinfections by assessing for spatial autocorrelation.

Results. Leprosy was associated with a 4.97 (1.03, 24.09) times higher odds of schistosomiasis infection compared to non-cases. Multibacillary leprosy was associated with a 5.28 (95% CI 1.49, 18.75) times higher odds of schistosomiasis compared to paucibacillary cases. The spatial scan statistic identified schistosomiasis and coinfection clusters, while the local join count statistic identified leprosy and schistosomiasis clusters, albeit in the same general vicinity. The Cuzick-Edwards method results showed global spatial autocorrelation in leprosy cases and schistosomiasis cases. The spatial scan and local join count identified clusters of infected and coinfected individuals in the same section of the study area.

Conclusion. We successfully described aspatial and spatial associations between leprosy and schistosomiasis infection in a coendemic area in Minas Gerais, Brazil. Furthermore, we estimated the aspatial association between multibacillary leprosy and schistosomiasis infection which supports the hypothesis that schistosomiasis may be a factor in the sustained transmission of leprosy in co-endemic areas.

Table of Contents

Table of Contents

Background 1

Methods 7

Results 12

Discussion 15

References 19

Figures and Figure Legends 23

Figure 1. The distribution of study participants in Minas Gerais, Brazil. 23

Figure 2. Bernoulli Spatial Scan Clusters of Schistosomiasis and Coinfections. 24

Figure 3. Local Join Count Cluster Cores. 25

Tables 26

Table 1. Demographic Data 26

Table 2. Logistic Regression Parameter Estimates 27

Table 3. Logistic Regression Odds Ratios for Schistosomiasis Infection 27

Table 4. Bernoulli Spatial Scan Clusters 28

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	Health Sciences, Public Health Health Sciences, Epidemiology
Keyword	neglected tropical diseases spatial epidemiology leprosy schistosomiasis GIS
Committee Chair / Thesis Advisor	Juan S. Leon, Emory University
Committee Members	Julie Clennon, Emory University Jessica Fairley, Emory University

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