全国血吸虫病疫情资料回顾性调查 Ⅰ传播阻断县达标前后疫情变化分析

Retrospective investigation on national endemic situation of schistosomiasis Ⅰ Analysis of changes of endemic situation in transmission-interrupted counties

目的分析我国血吸虫病传播阻断地区在达到传播阻断标准(传阻)前后的疫情变化规律,为今后修订传阻标准以及更科学、规范地考核和评价防治工作效果提供依据。方法选择全国9个省17个血吸虫病传阻县,采取回顾性调查方法,收集、记录各县达到传播控制标准(传控)前10年和以后各年(截止2008年或2009年)疫情资料并建立数据库;分析、比较达标前后不同流行类型和地区的各疫情指标的变化规律。结果达传阻后,各类型疫区人群感染率均降至最低水平,少部分湖沼型和山丘型疫区分别在传阻后4年和9年有小幅上升,但均<1%。湖沼型和水网型疫区活螺密度较高、变化较大,山丘型则较低并在传阻前后4年间降至最低;湖沼型疫区感染性钉螺时有发现,水网型和山丘型疫区则分别在达传阻后6年和10年发现有感染性钉螺复现。17个调查县从传控至传阻所历时间平均为17年。疫情非回升县达传阻前无感染性钉螺的平均持续时间为(2.71±1.10)年,其中湖沼型疫区为(3.80±1.43)年。结论达传阻后人群感染水平能维持在较低水平,而疫情回升主要表现在螺情回升。感染性钉螺可作为反映一个地区包括传染源控制等防治工作成效以及流行与传播危险程度的综合指标,持续而有效地控制感染性钉螺,是血吸虫病疫情达到传阻的基础。在我国目前社会经济发展水平和科学技术能力条件下,可将连续5年以上查不到感染性钉螺作为传阻标准之一。

Objective To analyze the changing rules of schistosomiasis endemic situation in the area of transmission that has been interrupted before and after they reach the criteria of transmission interruption,so as to offer the basis of amending to the criteria of schistosomiasis transmission interruption and a more scientific,standardized assessment and evaluation of the effects of schistosomiasis control in the future.Methods Nineteen counties of transmission that has been interrupted in 9 provinces nationwide were selected and investigated with the retrospective research method to collect and record the endemic detailed data 10 years before they reach the criteria of transmission interruption and several years later（ended in 2008 or 2009） and then a database was established.The changing rules of various disease indices in different endemic areas before and after reaching the criteria of transmission interruption were analyzed and compared.Results The average time from the transmission control to the transmission interruption was 17 years in the 17 counties.After reaching the criteria of transmission interruption,the infection rates of people turned down to a minimum level in various endemic areas,the infection rates in a few numbers of lake endemic areas and hilly endemic areas increased slightly after the transmission interruption 4-9 years later,but all of them were below 1%.The densities of living Oncomelania snails in lake endemic areas and water-network endemic areas were high and the changes were great each year,and the densities of living snails were much lower in hilly endemic areas than in the above two types of areas and they came to the lowest 4 years before and after the transmission interruption.The infected snails appeared occasionally in lake endemic areas,and they recurred 6 years and 10 years after the transmission interruption in water-network endemic areas and hilly endemic areas,respectively.The continued time without infected snails found before reaching transmission interruption was 2.71±1.10 years averagely in transmission-interrupted counties with endemic stable,and was 3.80±1.43 years in lake endemic areas.Conclusions It is possible to maintain a low level of population schistosome infection,and the endemic rebound is shown as snail rebound after the endemic areas reach the criteria of transmission interruption,The infected snails could be the comprehensive index reflecting the control achievement and the risk of schistosomiasis transmission.So the persistent control of infected snails is the fundament of schistosomiasis transmission interruption.It is suggested that in our current social and economic development and science and technology capacity conditions,the status of no infected snails found continuously for 5 years would be one of the criteria of schistosomiasis transmission interruption.