PDF(Pubmed)
Abstract：
BACKGROUND: Oncomelania hupensis is the exclusive intermediate host of Schistosoma japonicum in China. Snail control is an essential component of schistosomiasis elimination programme. With 70 years of continuous efforts, the range of O. hupensis had reduced significantly, but slowed down in last decades. A large number of levees against flooding were constructed along Yangtze River and its affiliated lakes in the middle and lower reaches, which influenced the hydrology and ecology in the alluvial plains. The purpose of this study was to assess the impact of levees on the distribution of O. hupensis in the middle and lower reaches of the Yangtze River.
METHODS: The snail habitats were digitalised by hand-held GPS system. The years for discovery and elimination of snail habitats were extracted from historical records. The accumulated snail-infested range for each habitat was calculated on the basis of annual reports. The current distribution of O. hupensis was determined by systematic and environmental sampling. The geographical distribution of levees was obtained from satellite imagery. To assess the impact of levees, the data pertaining to O. hupensis were divided into two parts: inside and outside the Yangtze River. Joinpoint regression was utilised to divide the study time span and further characterise the regression in each period. The 5-year-period moving averages of eliminated area infested by snails were calculated for the habitats inside and outside Yangtze River. The moving routes of corresponding geographical median centres were simulated in ArcGIS. Hotspot analysis was used to determine the areas with statistical significance clustering of O. hupensis density.
RESULTS: Three periods were identified according to Joinpoint regression both inside and outside Yangtze River. The area infested by O. hupensis increased in the first two periods. It decreased rapidly outside Yangtze River year over year after 1970, while that inside the Yangtze River did not change significantly. Furthermore, the latter was significantly higher than the former. It was observed that the present density of O. hupensis inside Yangtze River was lower than outside the Yangtze River. The median centre for eliminated ranges inside Yangtze River wavered between the east (lower reach) and the west (middle reach). In contrast, the median centre for eliminated ranges continuously moved from the east to the west.
CONCLUSIONS: Our findings indicated that the levees had a considerable negative impact on the distribution of O. hupensis outside Yangtze River. Some hotspots observed in the irrigation areas need a sluice system at the inlet of branch for snail control. The major distribution of O. hupensis located in Hubei might be caused by severe waterlogging. The intensive surveillance should be implemented there. The biggest two freshwater lakes, the major endemic regions historically, were identified as cold spots. The long-term impact of Three Gorges Dam on the distribution of O. hupensis in the lakes should be monitored and evaluated.
METHODS: The snail habitats were digitalised by hand-held GPS system. The years for discovery and elimination of snail habitats were extracted from historical records. The accumulated snail-infested range for each habitat was calculated on the basis of annual reports. The current distribution of O. hupensis was determined by systematic and environmental sampling. The geographical distribution of levees was obtained from satellite imagery. To assess the impact of levees, the data pertaining to O. hupensis were divided into two parts: inside and outside the Yangtze River. Joinpoint regression was utilised to divide the study time span and further characterise the regression in each period. The 5-year-period moving averages of eliminated area infested by snails were calculated for the habitats inside and outside Yangtze River. The moving routes of corresponding geographical median centres were simulated in ArcGIS. Hotspot analysis was used to determine the areas with statistical significance clustering of O. hupensis density.
RESULTS: Three periods were identified according to Joinpoint regression both inside and outside Yangtze River. The area infested by O. hupensis increased in the first two periods. It decreased rapidly outside Yangtze River year over year after 1970, while that inside the Yangtze River did not change significantly. Furthermore, the latter was significantly higher than the former. It was observed that the present density of O. hupensis inside Yangtze River was lower than outside the Yangtze River. The median centre for eliminated ranges inside Yangtze River wavered between the east (lower reach) and the west (middle reach). In contrast, the median centre for eliminated ranges continuously moved from the east to the west.
CONCLUSIONS: Our findings indicated that the levees had a considerable negative impact on the distribution of O. hupensis outside Yangtze River. Some hotspots observed in the irrigation areas need a sluice system at the inlet of branch for snail control. The major distribution of O. hupensis located in Hubei might be caused by severe waterlogging. The intensive surveillance should be implemented there. The biggest two freshwater lakes, the major endemic regions historically, were identified as cold spots. The long-term impact of Three Gorges Dam on the distribution of O. hupensis in the lakes should be monitored and evaluated.
摘要：
背景：钉螺是中国日本血吸虫的唯一中间宿主。蜗牛防治是血吸虫病消灭计划的重要组成部分。经过70年的不断努力，湖北的范围明显减少，但在过去的几十年里放慢了速度。沿江及中下游附属湖泊修建了大量抗洪堤防,影响了冲积平原的水文和生态。这项研究的目的是评估堤防对长江中下游湖北的分布的影响。
方法：通过手持GPS系统将蜗牛栖息地数字化。从历史记录中提取了发现和消除蜗牛栖息地的年份。每个栖息地的累积蜗牛出没范围是根据年度报告计算的。通过系统和环境采样确定了湖北的当前分布。堤防的地理分布是从卫星图像中获得的。为了评估堤坝的影响，与湖北有关的数据分为两个部分：长江内外。Joinpoint回归用于划分研究时间跨度，并进一步表征每个时期的回归。计算了长江内外栖息地的蜗牛出没面积的5年移动平均值。在ArcGIS中模拟了相应地理中位数中心的移动路线。使用热点分析来确定具有统计意义的区域。hupensis密度。
结果：根据Joinpoint回归确定了长江内外三个时期。前两个时期，湖北感染的面积增加了。1970年以后，长江外逐年迅速下降，而长江内没有明显变化。此外，后者明显高于前者。观察到长江内湖北的当前密度低于长江外。长江内部消除范围的中位数中心在东部（下游）和西部（中部）之间波动。相比之下,消除范围的中位数中心不断从东向西移动。
结论：我们的发现表明，堤防对长江外湖北的分布有相当大的负面影响。在灌溉区观察到的一些热点需要在分支入口处的水闸系统来控制蜗牛。湖北湖北的主要分布可能是由严重的内涝引起的。应该在那里进行密集的监视。最大的两个淡水湖，历史上主要的流行地区，被确定为冷点。三峡大坝对湖水分布的长期影响应进行监测和评估。
方法：通过手持GPS系统将蜗牛栖息地数字化。从历史记录中提取了发现和消除蜗牛栖息地的年份。每个栖息地的累积蜗牛出没范围是根据年度报告计算的。通过系统和环境采样确定了湖北的当前分布。堤防的地理分布是从卫星图像中获得的。为了评估堤坝的影响，与湖北有关的数据分为两个部分：长江内外。Joinpoint回归用于划分研究时间跨度，并进一步表征每个时期的回归。计算了长江内外栖息地的蜗牛出没面积的5年移动平均值。在ArcGIS中模拟了相应地理中位数中心的移动路线。使用热点分析来确定具有统计意义的区域。hupensis密度。
结果：根据Joinpoint回归确定了长江内外三个时期。前两个时期，湖北感染的面积增加了。1970年以后，长江外逐年迅速下降，而长江内没有明显变化。此外，后者明显高于前者。观察到长江内湖北的当前密度低于长江外。长江内部消除范围的中位数中心在东部（下游）和西部（中部）之间波动。相比之下,消除范围的中位数中心不断从东向西移动。
结论：我们的发现表明，堤防对长江外湖北的分布有相当大的负面影响。在灌溉区观察到的一些热点需要在分支入口处的水闸系统来控制蜗牛。湖北湖北的主要分布可能是由严重的内涝引起的。应该在那里进行密集的监视。最大的两个淡水湖，历史上主要的流行地区，被确定为冷点。三峡大坝对湖水分布的长期影响应进行监测和评估。
