Dissémination des bactéries pathogènes dans les hydrosystèmes tropicaux : transport et devenir d’Escherichia coli dans le bassin versant du Mékong au Laos

Soutenance de thèse de Paty Nakhle

Abstract Fecal contamination of surface water remains a major threat to public health especially in the rural areas of developing countries. Over 70 million people depend on unimproved water resources in the lower Mekong basin. Diarrheal diseases are a leading cause of death especially among children under age five, due to inadequate sanitation infrastructure, low access to safe water resources, and poor medical care in developing countries. Reducing the disease burden requires a better understanding of fecal pathogens dynamics in tropical context under the impact of rapid global changes. This research work is based on a multi-disciplinary approach (in situ monitoring, experimental, statistical and modelling approaches), aiming to identify key factors controlling the fate and transport of the fecal indicator bacteria, Escherichia coli (E. coli), at different spatial-temporal scales of major Mekong tributaries in Lao PDR. Our results reported seasonal variabilities of in-stream E. coli concentrations, and pointed out the importance of land use management as one of major factors affecting E. coli dissemination at watershed-scale in a tropical context prone to soil erosion. This work underlines the important role of total suspended sediments in providing attached E. coli protection from environmental stressors, and the transport within the watershed. At last, given the importance of the hydro-sedimentary dynamics on bacterial dissemination, we assessed the hydropower dam impact on the hydrology and water quality downstream of the dam. Overall, this thesis work provides new insights on fecal pathogen dynamics in a tropical context that could be helpful in establishing effective strategies for water resource management.

Le jury sera composé de 
M. Jean MARTINS (Directeur de recherche, CNRS, Rapporteur)
M. Kyunghwa CHO (Professeur associé, Ulsan National Institute of Science and Technology, Rapporteur)
M. Bruno LARTIGES (Professeur des universités, Université Toulouse III, Examinateur)
Mme Michelle GOURMELON (Chargée de recherche, IFREMER, Examinatrice)
Mme Emilie JARDE (Chargée de recherche, CNRS, Examinatrice)
Mme Emma ROCHELLE-NEWALL (Directrice de recherche, IRD, Examinatrice)
M. Olivier RIBOLZI (Directeur de recherche, IRD, Directeur de thèse)
Mme Laurie BOITHIAS (Physicienne-Adjointe, Université Toulouse III, Co-directrice de thèse)

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