Hydrological Regime and Water Shortage as Drivers of the Seasonal Incidence of Diarrheal Diseases in a Tropical Montane Environment.
Hydrological Regime and Water Shortage as Drivers of the Seasonal Incidence of Diarrheal Diseases in a Tropical Montane Environment.
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DOI：
10.1371/journal.pntd.0005195
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发表时间：
2016-12
影响因子：
3.8
通讯作者：
Ribolzi O
中科院分区：
文献类型：
--
作者：
Boithias L;Choisy M;Souliyaseng N;Jourdren M;Quet F;Buisson Y;Thammahacksa C;Silvera N;Latsachack K;Sengtaheuanghoung O;Pierret A;Rochelle-Newall E;Becerra S;Ribolzi O
全球腹泻负担是全世界发病率和死亡率的主要原因。在东南亚山地地区，如老挝北部，最近土地利用的变化导致径流、土壤侵蚀和河流悬浮泥沙负荷增加，并可能导致病原体传播。据我们所知，很少有研究将腹泻发病率与流域尺度的水文因素(如河流流量)、悬浮泥沙和粪便指示菌(FIB)(如大肠杆菌)的负荷，以及社会学因素(如卫生做法)联系起来。我们假设气候因素和人类行为相结合控制了腹泻的发病率，要么是因为更高的降雨量导致更高的河流流量、悬浮泥沙和FIB计数，要么是因为雨季报告的腹泻病例数量更多，或者是因为缺水导致在旱季使用更不安全的水源。因此，本研究的目的是(1)描述老挝北部地区腹泻的流行病学动态；(2)确定哪些水文气象和社会学危险因素与腹泻流行有关。考虑到两个面积分别为22和7,448平方公里的不相连河流流域，我们对老挝琅勃拉邦省南部5个地区的6个卫生院的气象变量(降雨量、气温)、水文变量(流量、悬沙、FIB计数、水温)以及报告的腹泻病例数量进行了回顾时间序列分析。我们还检查了可能影响易受气候因素影响的社会人口因素，如饮用水来源、卫生习惯和娱乐用水暴露。使用这种混合方法，我们发现大肠杆菌全年都存在(100-1,000个最可能数量或MPN 100毫升-1)，这表明粪便污染无处不在且持续存在。我们发现，在干旱时期，人们会将供水从井水转向地表水，后者似乎比市政饮水机受到细菌污染的风险更高。因此，我们发现琅勃拉邦地区的缺水在干燥和炎热的季节引发了腹泻高峰，而降雨和含水层的补给在雨季结束了疫情。报告的每日腹泻病例的时间趋势通常是双峰的，入院人数在2-3月达到高峰，5-7月晚些时候。年发病率在人口密度较高的地区较高，主要发生在0-4岁年龄组和男性患者。我们发现，在决定腹泻流行的季节模式方面，人为驱动因素，如卫生习惯，至少与环境驱动因素一样重要。对于腹泻病风险监测，可将流量或地下水位视为相关指标。应在预警系统的框架内监测这些变量，条件是在监测流域的大小和测量频率之间找到折衷办法。为了确定东南亚山区腹泻流行的最关键驱动因素，我们对老挝北部两个不同河流流域的腹泻报告病例和水文气象变量进行了追溯时间序列分析，并结合社会行为实践。我们发现，在干旱时期，人们将供水从井水切换到地表水，在地表水中我们测量了100-1,000 MPN 100毫升(世界卫生组织建议饮用水来源为0 MPN 100毫升-1)的粪便指示菌(E.Coli)数量。我们发现，缺水会在干燥和炎热的季节引发腹泻高峰，而降雨和随后的含水层补给在雨季结束了疫情。由于地表水中的大肠杆菌数量全年都很高，因此大肠杆菌可能不是该地区粪便风险的相关指标。相反，河流流量和含水层水位似乎是预测腹泻风险的相关指标。在全球变化的背景下，减少发展中国家粪便细菌传播的环境和人为驱动因素是至关重要的：更强的降雨加上易于径流的土地用途的扩大(例如，无林下植树)，可能会减少含水层的补给和污染物保留生态系统的服务，从而威胁到人口获得安全水资源。
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. We hypothesized that climate factors combined with human behavior control diarrhea incidence, either because higher rainfall, leading to higher stream discharges, suspended sediment loads and FIB counts, are associated with higher numbers of reported diarrhea cases during the rainy season, or because water shortage leads to the use of less safe water sources during the dry season. Using E. coli as a FIB, the objectives of this study were thus (1) to characterize the epidemiological dynamics of diarrhea in Northern Laos, and (2) to identify which hydro-meteorological and sociological risk factors were associated with diarrhea epidemics. Considering two unconnected river catchments of 22 and 7,448 km2, respectively, we conducted a retrospective time series analysis of meteorological variables (rainfall, air temperature), hydrological variables (discharge, suspended sediments, FIB counts, water temperature), and the number of diarrheal disease cases reported at 6 health centers located in the 5 southern districts of the Luang Prabang Province, Lao PDR. We also examined the socio-demographic factors potentially affecting vulnerability to the effect of the climate factors, such as drinking water sources, hygiene habits, and recreational water exposure. Using thus a mixed methods approach, we found E. coli to be present all year long (100–1,000 Most Probable Number or MPN 100 mL-1) indicating that fecal contamination is ubiquitous and constant. We found that populations switch their water supply from wells to surface water during drought periods, the latter of which appear to be at higher risk of bacterial contamination than municipal water fountains. We thus found that water shortage in the Luang Prabang area triggers diarrhea peaks during the dry and hot season and that rainfall and aquifer refill ends the epidemic during the wet season. The temporal trends of reported daily diarrhea cases were generally bimodal with hospital admissions peaking in February-March and later in May-July. Annual incidence rates were higher in more densely populated areas and mostly concerned the 0–4 age group and male patients. We found that anthropogenic drivers, such as hygiene practices, were at least as important as environmental drivers in determining the seasonal pattern of a diarrhea epidemic. For diarrheal disease risk monitoring, discharge or groundwater level can be considered as relevant proxies. These variables should be monitored in the framework of an early warning system provided that a tradeoff is found between the size of the monitored catchment and the frequency of the measurement. Aiming to identify the most critical drivers of diarrhea epidemics in montane areas of South-East Asia, we conducted a retrospective time series analysis of diarrhea reported cases and of hydro-meteorological variables measured in two contrasted river basins in northern Laos, together with socio-behavioral practices. We found that during drought periods, the population switches its water supply from wells to surface water where we measured numbers of fecal indicator bacteria (E. coli) of 100–1,000 MPN 100 mL-1 (the World Health Organization recommendation is 0 MPN 100 mL-1 in drinking water supply sources). We found that water shortages trigger diarrhea peaks during the dry and hot seasons and that rainfall and subsequent aquifer refill ends the epidemic during the wet season. As E. coli counts in surface water are high all year long, E. coli may not be a relevant indicator of the fecal risk in this area. Conversely, stream discharge and aquifer water level appear to be relevant proxies to predict diarrheal risk. Mitigating both environmental and anthropogenic drivers of fecal bacteria dissemination in developing countries is critical in the context of global change: more intense rainfall combined to the extension of run-off prone land uses (e.g. tree plantation without understorey) may decrease both the aquifer recharge and the contaminant retention ecosystem service, and thus threaten the availability of safe water resource for the population.
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