Mapping the potential risk of mycetoma infection in Sudan and South Sudan using ecological niche modeling.

Abdallah M Samy,Wendy W J Van De Sande,Ahmed Hassan Fahal,A Townsend Peterson,Pamela L C Small

doi:10.1371/journal.pntd.0003250

Abdallah M Samy, Wendy W J Van De Sande + Show 3 more

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https://doi.org/10.1371/journal.pntd.0003250

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Abstract

In 2013, the World Health Organization (WHO) recognized mycetoma as one of the neglected tropical conditions due to the efforts of the mycetoma consortium. This same consortium formulated knowledge gaps that require further research. One of these gaps was that very few data are available on the epidemiology and transmission cycle of the causative agents. Previous work suggested a soil-borne or Acacia thorn-prick-mediated origin of mycetoma infections, but no studies have investigated effects of soil type and Acacia geographic distribution on mycetoma case distributions. Here, we map risk of mycetoma infection across Sudan and South Sudan using ecological niche modeling (ENM). For this study, records of mycetoma cases were obtained from the scientific literature and GIDEON; Acacia records were obtained from the Global Biodiversity Information Facility. We developed ENMs based on digital GIS data layers summarizing soil characteristics, land-surface temperature, and greenness indices to provide a rich picture of environmental variation across Sudan and South Sudan. ENMs were calibrated in known endemic districts and transferred countrywide; model results suggested that risk is greatest in an east-west belt across central Sudan. Visualizing ENMs in environmental dimensions, mycetoma occurs under diverse environmental conditions. We compared niches of mycetoma and Acacia trees, and could not reject the null hypothesis of niche similarity. This study revealed contributions of different environmental factors to mycetoma infection risk, identified suitable environments and regions for transmission, signaled a potential mycetoma-Acacia association, and provided steps towards a robust risk map for the disease.

Highlights

Mycetoma is a chronic, devastating, inflammatory disease of the subcutaneous tissues that spread to involve the skin, deep structures and bones, and is characterized by deformity, destruction and disability especially in late stages [1,2,3]
We investigated risk factors associated with mycetoma infections in Sudan using ecological niche modeling (ENM), integrating mycetoma case records, Acacia records, and geospatial data summarizing soil, land-surface temperature, and greenness
ENMs calibrated in endemic districts were transferred across Sudan, and suggested that greatest risk was in a belt across central Sudan

Summary

Introduction

Mycetoma is a chronic, devastating, inflammatory disease of the subcutaneous tissues that spread to involve the skin, deep structures and bones, and is characterized by deformity, destruction and disability especially in late stages [1,2,3]. The organisms causing mycetoma are geographically distributed worldwide, but are common in tropical and subtropical areas, in the so-called ‘mycetoma belt,’ which includes Mexico, Venezuela, Mauritania, Senegal, Chad, Ethiopia, Sudan, Somalia, Yemen, and India [11]. The incidence and geographic distribution of mycetoma are underestimated, as the disease is usually painless and slowly progressive, such that it is presented to health centers only in late disease stages by most of patients; it is not a reportable disease [12,13,14]. Fungal infections responsible for eumycetoma in Sudan are predominantly caused by Madurella mycetomatis [4]

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