Expansion and transmission of M ulcerans in changing environments: multidisciplinary studies – EXTRA-MU

The last twenty years have seen the emergence or rediscovery of Buruli ulcer disease, a devastating skin infection caused by Mycobacterium ulcerans. This disease is characterized by progressive dermis infection causing extensive ulcerated lesions. Complications occur when bones, tendons are affected, and more than 50% of cases present incapacities after healing without additional care. It was described first in Uganda in the 60s and Central Africa, and is emerging in rural West Africa.

M. ulcerans is an aquatic environmental mycobacterium, distantly related to M. tuberculosis and M. leprae. Its transmission route remains elusive, but the water environment has been shown to play a major role in its focal distribution. In Ghana and Ivory Coast, two countries most affected by this disease, national scale studies have shown that the regions most impacted by the disease were the same regions where dams had been constructed and where irrigated agriculture was most developed. It is therefore suspected that the emergence of Buruli ulcer is related to the profound environmental modifications undergone by rural African landscapes over the last decades.

The aim of this project is to investigate the global correlations observed between human-made environmental changes such as dams, irrigation/agriculture, deforestation and endemic foci of this disease. The relationship between Buruli ulcer disease and environmental changes will be addressed in two historically endemic regions in different climates (equatorial and subtropical in Cameroon and Benin, respectively) and one newly discovered endemic focus close to a dam (in Cameroon).

The program originality relies on the simultaneous collection of environmental, entomological, epidemiological and microbiological data from the same field study sites, their parallel processing by various methods and their final integration through mapping and modelling. Several disciplinary fields will interact and complement each other strongly during data collection and at every step of each task: environmental scientists specializing in ecology and geomatics will work closely with field botanists, entomologists and biologists, as well as epidemiologists, anthropologists and microbiologists. Most have a long history of collaborative work on Buruli ulcer attested by a large number of co-authored scientific publications.

Finally, maps of M. ulcerans presence probability, as well as of M. ulcerans exposure risk will be produced at the regional scale and tentatively expanded at the national or supranational scale. Furthermore, understanding of the seasonal dynamics of M. ulcerans presence in the environment will allow recommendations to help population to prevent the disease in endemic regions and to limit the impact of environmental modifications on its spread. These space-time data on M. ulcerans presence and Buruli ulcer disease risk will be designed to be easily handled by public health actors, such as national Buruli ulcer control program officials or NGO personnel. This mapping will allow targeting of interventions such as active case detection or awareness campaigns to the areas identified as presenting the greatest risks. Feedback from Buruli ulcer diagnostic and treatment programs will allow model fine-tuning using field data.