Village Settlements in Mountainous Tropical Areas, Hotspots of Fecal Contamination as Evidenced by and Stanol Concentrations in Stormwater Pulses.

Fecal bacteria in surface water may indicate threats to human health. Our hypothesis is that village settlements in tropical rural areas are major hotspots of fecal contamination because of the number of domestic animals usually roaming in the alleys and the lack of fecal matter treatment before entering the river network. By jointly monitoring the dynamics of and of seven stanol compounds during four flood events (July-August 2016) at the outlet of a ditch draining sewage and surface runoff out of a village of Northern Lao PDR, our objectives were (1) to assess the range of concentration in the surface runoff washing off from a village settlement and (2) to identify the major contributory sources of fecal contamination using stanol compounds during flood events.

Distribution of Burkholderia pseudomallei within a 300-cm deep soil profile: implications for environmental sampling.

The environmental distribution of Burkholderia pseudomallei, the causative agent of melioidosis, remains poorly understood. B. pseudomallei is known to have the ability to occupy a variety of environmental niches, particularly in soil.

Experimental and modelling evidence of splash effects on manure borne Escherichia coli washoff.

In tropical montane South-East Asia, recent changes in land use have induced increased runoff, soil erosion and in-stream suspended sediment loads. Land use change is also contributing to increased microbial pathogen dissemination and contamination of stream waters. Escherichia coli (E.

Effects of hydrological regime and land use on in-stream Escherichia coli concentration in the Mekong basin, Lao PDR.

In the basin of Mekong, over 70 million people rely on unimproved surface water for their domestic requirements. Surface water is often contaminated with fecal matter and yet little information exists on the underlying mechanisms of fecal contamination in tropical conditions at large watershed scales. Our objectives were to (1) investigate the seasonality of fecal contamination using Escherichia coli as fecal indicator bacteria (FIB), and (2) establish links between the fecal contamination in stream water and its controlling factors (hydrology and land use).

Whole-Genome Assemblies of 16 Burkholderia pseudomallei Isolates from Rivers in Laos.

We report 16 genomes, including 5 new multilocus sequence types, isolated from rivers in Laos. The environmental bacterium causes melioidosis, a serious infectious disease in tropical and subtropical regions. The isolates are geographically clustered in one clade from around Vientiane, Laos, and one clade from further south.

Modeling the Impact of Land Use Change on Basin-scale Transfer of Fecal Indicator Bacteria: SWAT Model Performance.

Land use change from annual crops to commercial tree plantations can modify flow and transport processes at the watershed scale, including the fate and transport of fecal indicator bacteria (FIB), such as . The Soil and Water Assessment Tool (SWAT) is a useful means for integrating watershed characteristics and simulating water and contaminants. The objective of this study was to provide a comprehensive assessment of the impact of land use change on microbial transfer from soils to streams using the SWAT model.

Vicinal land use change strongly drives stream bacterial community in a tropical montane catchment.

Impact of land use (LU) change on stream environmental conditions and the inhabiting bacterial community remains rarely investigated, especially in tropical montane catchments. We examined the effects of LU change and its legacy along a tropical stream by comparing seasonal patterns of dissolved organic carbon (DOC) / colored dissolved organic matter (CDOM) in relation to variations in structure, diversity and metabolic capacities of particle-attached (PA) and free-living (FL) bacterial communities. We hypothesized that despite seasonal differences, hydrological flows that accumulate allochthonous carbon along the catchment are a major controlling factor of the bacterial community.

Rivers as carriers and potential sentinels for Burkholderia pseudomallei in Laos.

Burkholderia pseudomallei, causative agent of the often fatal disease melioidosis, dwells in tropical soils and has been found in freshwater bodies. To investigate whether rivers are potential habitats or carriers for B. pseudomallei and to assess its geographical distribution in Laos, we studied 23 rivers including the Mekong, applying culture-based detection methods and PCR to water filters and streambed sediments.

Linking crop structure, throughfall, soil surface conditions, runoff and soil detachment: 10 land uses analyzed in Northern Laos.

In Montane Southeast Asia, deforestation and unsuitable combinations of crops and agricultural practices degrade soils at an unprecedented rate. Typically, smallholder farmers gain income from "available" land by replacing fallow or secondary forest by perennial crops. We aimed to understand how these practices increase or reduce soil erosion.

From shifting cultivation to teak plantation: effect on overland flow and sediment yield in a montane tropical catchment.

Soil erosion supplies large quantities of sediments to rivers of Southeastern Asia. It reduces soil fertility of agro-ecosystems located on hillslopes, and it degrades, downstream, water resource quality and leads to the siltation of reservoirs. An increase in the surface area covered with commercial perennial monocultures such as teak plantations is currently observed at the expanse of traditional slash-and-burn cultivation systems in steep montane environments of these regions.

Hydrological modeling of Fecal Indicator Bacteria in a tropical mountain catchment.

The occurrence of pathogen bacteria in surface waters is a threat to public health worldwide. In particular, inadequate sanitation resulting in high contamination of surface water with pathogens of fecal origin is a serious issue in developing countries such as Lao P.D.

Hydrological Regime and Water Shortage as Drivers of the Seasonal Incidence of Diarrheal Diseases in a Tropical Montane Environment.

Background: The global burden of diarrhea is a leading cause of morbidity and mortality worldwide. In montane areas of South-East Asia such as northern Laos, recent changes in land use have induced increased runoff, soil erosion and in-stream suspended sediment loads, and potential pathogen dissemination. To our knowledge, few studies have related diarrhea incidences to catchment scale hydrological factors such as river discharge, and loads of suspended sediment and of Fecal Indicator Bacteria (FIB) such as Escherichia coli, together with sociological factors such as hygiene practices.

Effect of land use and hydrological processes on Escherichia coli concentrations in streams of tropical, humid headwater catchments.

Lack of access to clean water and adequate sanitation continues to be a major brake on development. Here we present the results of a 12-month investigation into the dynamics of Escherichia coli, a commonly used indicator of faecal contamination in water supplies, in three small, rural catchments in Laos, Thailand and Vietnam. We show that land use and hydrology are major controlling factors of E.

Modelling of faecal indicator bacteria (FIB) in the Red River basin (Vietnam).

Many studies have been published on the use of models to assess water quality through faecal contamination levels. However, the vast majority of this work has been conducted in developed countries and similar studies from developing countries in tropical regions are lacking. Here, we used the Seneque/Riverstrahler model to investigate the dynamics and seasonal distribution of total coliforms (TC), an indicator of faecal contamination, in the Red River (Northern Vietnam) and its upstream tributaries.

Land use and soil type determine the presence of the pathogen Burkholderia pseudomallei in tropical rivers.

Burkholderia pseudomallei is the bacterium that causes melioidosis in humans. While B. pseudomallei is known to be endemic in South East Asia (SEA), the occurrence of the disease in other parts of the tropics points towards a potentially large global distribution.

Use of fallout radionuclides ((7)Be, (210)Pb) to estimate resuspension of Escherichia coli from streambed sediments during floods in a tropical montane catchment.

Consumption of water polluted by faecal contaminants is responsible for 2 million deaths annually, most of which occur in developing countries without adequate sanitation. In tropical aquatic systems, streambeds can be reservoirs of persistent pathogenic bacteria and high rainfall can lead to contaminated soils entering streams and to the resuspension of sediment-bound microbes in the streambed. Here, we present a novel method using fallout radionuclides ((7)Be and (210)Pbxs) to estimate the proportions of Escherichia coli, an indicator of faecal contamination, associated with recently eroded soil particles and with the resuspension of streambed sediments.

A short review of fecal indicator bacteria in tropical aquatic ecosystems: knowledge gaps and future directions.

Given the high numbers of deaths and the debilitating nature of diseases caused by the use of unclean water it is imperative that we have an understanding of the factors that control the dispersion of water borne pathogens and their respective indicators. This is all the more important in developing countries where significant proportions of the population often have little or no access to clean drinking water supplies. Moreover, and notwithstanding the importance of these bacteria in terms of public health, at present little work exists on the persistence, transfer and proliferation of these pathogens and their respective indicator organisms, e.

Evaluation of Molecular Methods To Improve the Detection of Burkholderia pseudomallei in Soil and Water Samples from Laos.

Burkholderia pseudomallei is the cause of melioidosis, a severe and potentially fatal disease of humans and animals. It is endemic in northern Australia and Southeast Asia and is found in soil and surface water. The environmental distribution of B.

Land use and water quality along a Mekong tributary in northern Lao P.D.R.

Improving access to clean water has the potential to make a major contribution toward poverty reduction in rural communities of Lao P.D.R.

Trapping efficiencies of cultivated and natural riparian vegetation of northern Laos.

In northern Laos, intensification of cultivation on sloping land leads to accelerated erosion processes. Management of riparian land may counteract the negative impacts of higher sediment delivery rates on water quality. This study assessed water and sediment concentration trapping efficiencies of riparian vegetation in northern Laos and the effect of cultivation of riparian land on water quality.