Abstract: Objective To understand the Oncomelania hupensis snail distribution in the working areas of Yangtze River hy? drologic agencies located in the middle and lower reaches of the Yangtze River in 2016，so as to provide the evidence for assess? ing the risk of schistosome infection of hydrological workers and establishing the control strategies. Methods The suspicious en? vironments with O. hupensis snails in the above working areas were selected as study areas，and the snail situation was surveyed by the system sampling method combined with the environmental sampling method. The survey data were collected and analyzed statistically. Results Totally 19 working areas from 17 hydrological agencies were selected as the investigation sites，among which，10 working areas from 9 agencies were found with O. hupensis snail distribution. The constituent ratio of the areas with snails reached to 38.81% of the investigation areas，the occurrence rate of frames with snails was 3.08%，and the average densi? ty of living snails was 0.07 /0.1 m2. By comparison，the average density of living snails and occurrence rate of frames with snails in hydrological agencies under the jurisdiction of the Middle Reaches Administrative Bureau were the most serious among three administrative bureaus of the Yangtze River Water Resources Commission. Conclusions There are various degrees of O. hupen? sis breeding in the working areas of hydrological agencies located in the middle and lower reaches of the Yangtze River，and the hydrological workers are facing with the risk of schistosome infection.

Key words: Oncomelania hupensis snail；Distribution investigation；Hydrological agency；Working area；Middle and lower reaches of Yangtze River

摘要： 目的掌握长江中下游长江水利委员会（长江委）所属水文机构工作区钉螺分布状况，为评估水文工作人员血 吸虫感染风险和制订防治对策提供科学依据。方法对上述水文机构工作区域的可疑环境采用系统抽样结合环境抽样 法进行查螺，对所得数据进行统计分析。结果共调查了17个水文机构的19处工作现场，查出9个水文机构的10处工 作现场有钉螺孳生。有螺面积查出比例达38.81%，活螺框出现率为3.08%，平均活螺密度为0.07只/0.1 m2，其中所处中 游的水文机构工作区的平均活螺密度和活螺框出现率最高。结论长江中下游长江委所属部分水文机构工作区域有不 同程度的钉螺孳生，水文工作人员面临血吸虫感染风险。

关键词: 钉螺；分布调查；水文机构；工作区；长江中下游