Abstract:

Objective To investigate and analyze the schistosomiasis endemic status and influencing factors in areas of schistosomiasis transmission control in hilly regions of mountain areas，so as to provide the reference for establishing the strategy and measures to achieve the target of schistosomiasis transmission?interrupted in the similar areas. Methods Dongpo District of Meishan City，Sichuan Province，which was appropriate to the standards of schistosomiasis transmission controlled by national evalua? tion in 2008，was selected as a study area. The data of schistosomiasis control from 2008 to 2010 were collected. A survey for epidemiological factors was carried out from April to November in 2011. The survey of Oncomelania snails was performed with the systematic sampling combined with environmental method. The schistosome infection status of residents was investigated by the seroimmunological test and fecal hatching examination. The schistosome infection status of cattle was investigated by the plastic cup with top tube hatching method. The infested water contact of residents was investigated with questionnaire. At the same time，in 2011，a simple random sampling combined with rapid field assessment method was used to investigate the distribution of outdoor feces，outdoor feces containing schistosome eggs，snails and infected snails in two spots of Jingyang District，Deyang City and Renshou County，Meishan City which had been appropriate to the standards of schistosomiasis transmission controlled in 2006 and 2007 respectively. Results From 2008 to 2010，182.6 thousand-213.3 thousand local residents were examined in Dongpo District，the positive rate of sero?immunological tests of population was 6.30% - 6.81%，and the infection rate of population was 0.02% -0.07% by estimated calculation. Totally 2 835-7 260 heads of cattle were examined and no positive cases were found. The areas of snail habits were 190.00 - 232.00 hm2 ，the intensities of living snails were 0.02 - 0.19 snails/0.1 m2 ，and no infected snails were found. In 2011，totally 204.4 thousand residents were examined and the positive rate of sero? immunological tests of population was 4.98% but no positive cases were founded through the parasitological tests. A total of 1 735 heads of cattle were ex? amined and no positive cases were found. The areas of snail habits were 99.00 hm2 ，the intensity of living snails was 0.18 snails/ 0.1 m2 ，and no infected snails were found. Questionnaire analyses of a total of 537 residents in 4 villages showed that ditch，channel，pond，and paddy field were the major environments of the infested water contact of the residents. In the ditches and paddy fields，the average annual median values of water contact of residents were 15 and 20 person?times respectively before the area was appropriate to the standards of schistosomiasis transmission controlled，and 20 and 30 person?times respectively after the area was appropriate to the standards of schistosomiasis transmission controlled，and there were no significant differences（ χdit ch 2 = 1.61，χpadd field 2 = 0.03，both P＞0.05） . Whereas，in the channels and ponds，the average annual median values of water contact were 15 and 30 person?times respectively before the area was appropriate to the standards of schistosomiasis transmission controlled，but they were significantly reduced after the area was appropriate to the standards of schistosomiasis transmission controlled（χch annel 2 =10.35，χpond 2 =18.69，both P< 0.01） . In 2011，the rapid field investigation and assessment showed that the average appearance rates of snails through screening were 60.15% and 12.12% respectively in the 2 villages. The average densities of living snails were 1.19 snails/0.1m2 and 0.20 snails/0.1m2 respectively in the 2 villages，and there were no infected snails. A total of 78 outdoor feces of cattle and sheep were collected and the fecal hatching examinations showed that there were no positives. Conclusions After the schistosomiasis endemic areas in hilly regions of mountain areas are appropriate to the standards of schistosomiasis transmission controll，the achievements have been consolidated. However，the potential schistosomiasis endemic factors still exist，such as the high positive rate of schistosome sero? immunological tests in population，frequently bovine flowing， and no obviously decrease of the snail area and density of living snails. Therefore，it is an urgent need to develop more suitable new technologies and measures to accelerate the process of schistosomiasis prevention and control.

Key words: Schistosomiasis； Transmission controlled； Transmission risk；Endemic factors；Hilly region of mountain area

摘要：

目的 调查与分析山区丘陵型血吸虫病流行区达到传播控制标准 （传控达标） 后疾病流行现状及影响因素， 为同类地区制定实现传播阻断目标的策略和措施提供参考依据。方法 选择2008年传控达标的四川省眉山市东坡区为研究区， 收集2008-2010年血吸虫病疫情资料； 于2011年4-11月开展血吸虫病流行因素现况调查， 采用系统抽样结合环境抽查法调查钉螺分布情况， 采用血清免疫学和粪便孵化法筛查当地常住居民血吸虫感染情况， 采用塑料杯顶管孵化法普查散养耕牛血吸虫感染情况， 采用问卷法调查当地居民疫水接触情况。选择2006年传控达标的德阳市旌阳区和2007年传控达标的眉山市仁寿县的2个村为传播风险快速评估调查点， 采用简单随机抽样结合快速现场评估方法， 于2011年对钉螺和感染性钉螺分布、 野粪和含血吸虫卵野粪分布等情况进行调查。结果 2008-2010年眉山市东坡区检查居民18.26万～ 21.33万人， 人群血检阳性率为6.30%～6.81%， 血吸虫感染率为0.02%～0.07%； 共检查耕牛2 835～7 260头， 未发现血吸虫感染病畜； 发现钉螺面积190.00～232.00 hm2 ， 活螺密度0.02～0.19只/0.1 m2 ， 未发现感染性钉螺。2011年， 东坡区共检查居民20.44万人， 血检阳性率为4.98%， 未发现粪检阳性者； 普查散放耕牛1 735头， 未发现粪检阳性牛； 共查出有螺面积 99.00 hm2 ， 活螺密度为0.18只/0.1 m2 ， 未发现感染性钉螺； 共在4个村对537名居民进行问卷调查， 沟、 渠、 塘、 水田等是当地居民主要接触疫水环境， 其中沟和水田环境在传控达标前和达标后的年平均接触频次中位数分别为20、 30人次和15、 30 人/次 （χ沟 2 =1.61，χ水田 2 =0.03，P均＞0.05）； 渠和塘达标前年平均接触频次中位数分别为15人次和30人次， 而在达标后则明显减少 （χ渠 2 =10.35，χ塘 2 =18.69 ， P均 < 0.01）。2011年2个村的快速评估调查显示， 有螺框平均出现率分别为60.15%和 12.12%， 活螺平均密度分别为1.19只/0.1 m2 和0.20只/0.1 m2 ， 均未发现感染性钉螺； 共采集牛、 羊等野粪78份， 经孵化检查未发现阳性。结论 山区丘陵型血吸虫病流行区传控达标后， 防治成果较为巩固， 但潜在流行因素依然存在， 表现为人群血检阳性率较高， 耕牛数量较多， 潜在传染源依然存在； 钉螺面积和活螺密度下降不明显。提示亟需开发、 研究更适宜的防治新技术和新措施， 加快推进山丘地区的血防工作进程。

关键词: 血吸虫病； 传播控制； 传播风险； 流行因素； 山区丘陵型