基于风险评价的血吸虫病防治措施区划研究

Schistosomiasis in China has been in the situation of a low prevalence in large areas and a resurgence risk in few regions. To achieve the goal of schistosomiasis elimination, it’s particularly important to implement precision control measures with more precise identification of control targets. We have been fully implemented the integrated strategy for schistosomiasis control with focus on infectious source control and will insist it for a long time, but how to scientifically give classified guide and reasonable allocate the limited resources as to achieve optimal combination of the intervention measures under different natural and cultural environment was proposed. Based on the current classification of schistosomiasis endemic regions, this project intends to introduce the concept of regionalization into the optimization study of integrated prevention and control measures of schistosomiasis. First, the Schistosomiasis epidemics comprehensive index will be proposed. Then, the Geographically and Temporally Weighted Regression and the Hierarchical Bayesian Spatiotemporal Model will be used to reveal the relationship between environmental and sociological factors and the distribution and growth of the index in order to obtaining risk factors. On this basis, we will discuss the mode of interventions’ regionalization, using the risk factors and the corresponding intervention measures as zoning indices. The regionalization result will be the personalized control scheme for each region according to its individual risk characteristics, that could provide scientific guidance to the rational layout of integrated control strategy for schistosomiasis control. This study is a response and an attempt to the advocation of precision schistosomiasis control and strengthening the application-oriented research on the prevention and treatment of schistosomiasis in China.

我国血吸虫病疫情已处于大范围低度流行、局部地区存在复燃风险的状态，为实现消除血吸虫病的目标，精确定位防治靶点、实施精准防治显得尤为重要。血吸虫病防治工作中已全面实施并将长期坚持“以控制传染源为主的综合防治策略”，但面临如何科学地分类指导、合理配置有限的血防资源，实现不同自然及人文环境下各干预措施优化组合的问题。本项目拟在现有血吸虫病流行区分类的基础上，将区划的理念引入到血吸虫病综合防治措施优化研究中，首先提出血吸虫病疫情综合指标的概念，运用时空地理加权回归模型和层次贝叶斯时空模型解析影响其分布及消长的环境与社会经济因子，基于此，探讨以风险因子及其相对应的干预措施为区划指标进行防治措施综合区划的模式。区划成果即根据每个区域的个体化风险特征因地制宜地制定个性化防治方案，可为干预措施优化组合提供科学依据。本研究是对我国血吸虫病防治新形势下提倡精准血防、加强血防应用型研究的响应和尝试。

为精准定位血吸虫病防治靶点，本项目首先开展社会经济因素回顾性调查，调查中发现多数地区血防意识有削弱倾向、改厕普遍落实不到位、灭螺方法实施不科学等特征且存在地区差异。同时，搜集多年血吸虫病疫情各个指标数据并分析其时空格局，结果显示，调查初始年（2012年）综合疫情最为严重，疫情指数极高值区（0.50-0.69）散布在东荆河沿岸、潜江市中南部、长江洪湖市段、长江石首市段及松滋市中部，占流行村的3.4%；此后血吸虫病疫情综合指数逐年降低，至2016年用于计算综合疫情指数的7个指标，包括居民血吸虫病感染率、突发疫情数、急性血吸虫病例数、家畜血吸虫病感染率、感染螺密度、感染螺面积和钉螺感染率等均为0。因此，重点解析螺情时空变化及其影响因素，在此基础上制定钉螺综合防治措施区划方案。首先，将1985年-2015年每间隔五年村级螺情资料与村级土地利用（水田、旱地面积占比）、景观指标、植被指数NDVI、地表湿度、与长江的距离、是否灭螺等空间关联，构建并求解了活螺密度及有螺面积的多水平模型，主要结论如下：活螺密度及有螺面积经过多年控螺措施均有所降低，但活螺密度的时间变异明显，而有螺面积的区域差异明显。螺情较轻的地区，灭螺效果不如螺情较严重的地区。长江水位影响钉螺孳生环境且距长江的越远影响程度随小。灭螺措施对活螺密度降低的累积效果较有螺面积显著。植被生长良好的环境对钉螺密度及面积均有积极影响。越是不规则（如狭长）的钉螺孳生地钉螺密度越大，但钉螺面积越小。景观越是破碎、旱地占比越大的村钉螺面积越小，但这些宏观环境指标对钉螺密度无影响。基于反映螺情时空动态、自然环境适宜性及钉螺防控措施实施效果等方面特征指标，构建了钉螺防控分区指标体系，将江汉平原钉螺防控划分为三个一级分区和7个二级分区。本项目关于血吸虫病及唯一中间宿主钉螺的时空格局分析、自然和社会经济环境因子的解析以及基于以上研究的防治区划方案的制定可为当前“精准血防”提供有力支撑和技术保障。