Dissemination of pathogenic bacteria in tropical hydrosystems: transport and fate of Escherichia coli in the Mekong watershed in Lao PDR

Paty Nakhle, PhD student within M-TROPICS CZO, defended her PhD thesis today at GET.

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 a tropical context, under the impact of a rapid global change. In this thesis based on a multi-disciplinary approach (in situ monitoring, experimental, statistical and modelling approaches), Paty aimed at identifying the key factors controlling the fate and transport of the fecal indicator bacteria, Escherichia coli (E. coli), at different spatial and temporal scales of the major Mekong tributaries in Lao PDR. Her 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. Paty underlined 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, Paty assessed the impact of a hydropower dam on the hydrology and water quality downstream of the dam. Overall, her 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.

Congratulations Paty!

More news


M-TROPICS was in the spotlight at the OZCAR annual meeting 2022

Emma Rochelle-Newall (iEES Paris-IRD) gave a talk as ‘Grand Témoin’ at the OZCAR annual meeting in Vogüé, Ardèche (March 7-10). She explained how sediment and their interactions with pollutants influence ecosystem and human health, and she took examples from the many studies carried out by M-TROPICS in Lao PDR and Vietnam.



Handing over of equipment to DALaM and MouNoy Dev

As part of the long-term collaboration between IRD (UMRs iEES-Paris and GET) and its Lao partners, which has resulted into the implementation of several partnership instruments such as the JEAI-EcoRubber, the LMI LUSES, and more recently the PSF-Sud AgreesLao, GDRI CompacSol, as well as the CZO M-TROPICS and the SEALNET network, in January 2022 research/production […]



Land use, surface runoff, soil erosion: multi-scale impact assessment of teak tree plantation management in a tropical humid mountainous agro-ecosystem

Layheang Song, PhD student within M-TROPICS CZO, defended his thesis today at GET. His thesis work was under the international double degree program between the University Paul Sabatier and the Institute of Technology of Cambodia. Soil erosion is one of the most concerning environmental problems on the global scale. Soil erosion is increasingly driven by […]