Abstract
The Buruli ulcer is an emerging environmentally acquired infectious neglected tropical disease. It causes permanent disability and disfigurement in victims. The causative agent is Mycobacterium ulcerans; however the environmental reservoir and mode of transmission of this bacterium are not known. Attempts to manage the disease have been hampered by lack of knowledge of the mode of transmission and the environmental reservoir of M. ulcerans. Certain environments have been associated with the disease, notably disturbed aquatic environments composed of small bodies of stagnant water. There is no known vector, though aquatic insects have been implicated as possible vectors. A full understanding of the distribution and mode of transmission of the bacterium would help in management of the disease.In this thesis, we use the tools developed in ecological niche modelling to describe the distribution of M. ulcerans. Following the construction of a model in Cameroon, Central Africa, and tested against a second database in French Guiana (South America), the pathogen is found to have notable seasonal changes in its distribution in our study sites in Cameroon. In the wet season, M. ulcerans is more common in large watersheds, while in the dry season the bacterium is more common in small watersheds. This enabled the generation of hazard maps of the pathogen distribution in the study region, which will be used in future studies and management of the disease. Following this we undertook ecological niche modelling to describe the distribution of the aquatic insects suspected to be vectors of M. ulcerans. Based on a sampling protocol that spanned the country of Cameroon, we undertake maximum entropy modelling, which enabled us to interpolate our model across all of West Africa. With these maps we explore the correlation between the predicted distribution of the insects to the prevalence of the Buruli ulcer. We find a significant positive correlation between the distribution of the insects and the distribution of the disease, and find that this correlation undergoes significant changes in space and time, consistent with the model of multi-vectorial transmission of the disease.Finally, in collaboration with other authors, we have assisted in exploring how the distribution of M. ulcerans changes according to community structure networks, how the distribution of the Buruli ulcer disease changes in our study region of Akonolinga, Cameroon, and how the distribution of the disease changes at a larger scale, between Benin and Nigeria. This thesis contributes to our understanding of the distribution and drivers of Mycobacterium ulcerans and the Buruli ulcer, providing evidence of multi-vectorial transmission of the disease, and the first hazard maps of the pathogen for Akonolinga, Cameroon.