Landscape and environmental influences on Mycobacterium ulcerans distribution among aquatic sites in Ghana.

Shannon M Pileggi,Charles Quaye,Pamela Small,Daniel Boakye,William Opare,Jenni Gronseth,Ellen Whitney,Jiaguo Qi,Ryan Kimbirauskas,M Eric Benbow,Heather Jordan,Lance A Waller,Julie A Clennon,Mollie Mcintosh,Lindsay Campbell,Edwin Ampadu,Richard Merritt,Ulrike Gertrud Munderloh

doi:10.1371/journal.pone.0176375

Abstract

Buruli ulcer, caused by Mycobacterium ulcerans, is highly endemic in West Africa. While the mode of transmission is unknown, many studies associate Buruli ulcer with different types of water exposure. We present results from the largest study to date to test for M. ulcerans in aquatic sites and identify environmental attributes associated with its presence. Environmental samples from 98 aquatic sites in the Greater Accra, Ashanti, and Volta regions of Ghana were tested for the presence of M. ulcerans DNA by polymerase chain reaction. The proportion of aquatic sites positive for M. ulcerans varied by region: Ashanti 66% (N = 39), Greater Accra 34% (N = 29), and Volta 0% (N = 30). We explored the spatial distribution of M. ulcerans positive and negative water bodies and found no significant clusters. We also determined both highly localized water attributes and broad scale remotely sensed land cover and terrain environmental characteristics associated with M. ulcerans presence through logistic regression. Our results concur with published results regarding conditions suitable for M. ulcerans growth and associations with Buruli ulcer disease burden with regards to water characteristics and disturbed environments, but differ from others with regards to spatial associations and topographic effects such as elevation and wetness. While our results suggest M. ulcerans is an environmental organism existing in a specific ecological niche, they also reveal variation in the elements defining this niche across the sites considered. In addition, despite the causal association between Buruli ulcer and M. ulcerans, we observed no significant statistical association between case reports of Buruli ulcer and presence of M. ulcerans in nearby waterbodies.

Highlights

Buruli ulcer (BU) is a neglected tropical disease (NTD) caused by infection with Mycobacterium ulcerans
Though no cases of BU had been reported from the Volta region during our study period, we sought to determine if this was due to the absence of M. ulcerans in the Volta region
For the present study, data from the Volta region were excluded from further analyses in order to investigate factors relating to variation in M. ulcerans presence

Summary

Introduction

Buruli ulcer (BU) is a neglected tropical disease (NTD) caused by infection with Mycobacterium ulcerans. This potentially debilitating skin disease often begins as a painless nodule and if left untreated can ulcerate, resulting in permanent scarring and disability [1]. BU cases have been reported in at least 31 countries spread across Africa, Asia, Australia, and Latin America, demonstrating increasing prevalence and expanding geographic distribution during the past century [3]. Accurate surveillance data reflecting the true disease incidence in West Africa remains elusive due to local variations in aspects such as case confirmation, access to care, diagnosis, and reporting practices

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