Objective: To investigate the spatiotemporal distribution of Oncomelania hupensis snails and infected snails in the endemic areas of schistosomiasis in Anhui Province.
Methods: Based on the snail survey data in Anhui Province in 2016, the distribution of snails and infected snails were analyzed, and the spatial distribution of snails and spatial cluster patterns of infected snails were investigated in snail habitats in Anhui Province from 1950 to 2016.
Results: A total of 22 757 snail habitats and 5 004 infected snail habitats were identified in Anhui Province from 1950 to 2016, which appeared single-peak and double-peak patterns, with an inflection point seen in 1970. There were 141 000 hm2 historically accumulative snail habitats, 88.08% of which were firstly identified from 1950 to 1979, and totally 114 500 hm2 snail habitats were eradicated, 77.17% of which were eradicated from 1970 to 1999. There were 4 830 snail habitats identified until 2016, in which 1 051 were once detected with infected snails. In addition, 78.12% of current snail habitats had been present for over 40 years, and infected snails had been eliminated in 65.75% of the infected snail habitats within 10 years. There was a spatial autocorrelation of the living snail density in current snail habitats in Anhui Province (Moran's I = 0.196, Z = 139.63, P < 0.001), and local hotspot analysis showed spatial clusters of living snails density in snail habitats, with high-value clusters in south of the Yangtze River and low-value clusters in north of the Yangtze River. The 21 high-value clusters of living snail density with statistical significance were distributed along the Yangtze River basin and its branches. Spatiotemporal scan analysis revealed spatiotemporal clusters of infected snails in 4 current snail habitats.
Conclusions: The current snail habitats have been present for a long period of time, and snails are difficult to be eliminated by chemical treatment alone, which requires the combination of environment improvements. There are spatial clusters of living snail density in current snail habitats in Anhui Province. The epidemic factors and risk of human and animal infections still remain in some clusters of historical infected snail habitats revealed by spatiotemporal scan analysis, which should be consid- ered as the key target areas for snail control in Anhui Province.
［摘要］ 目的 了解安徽省血吸虫病流行区钉螺及感染性钉螺时空分布特征。方法 根据 2016 年安徽省钉螺调查建 立的数据库, 描述全省钉螺及感染性钉螺分布和变化趋势, 分析有螺环境中钉螺空间分布和感染性钉螺在 1950–2016 年 聚集分布情况。结果 1950–2016 年, 安徽省共发现钉螺孳生环境 22 757 个, 其中曾为感染性钉螺环境 5 004 个, 分别呈 单峰和双峰状变化, 1970 年是变化拐点; 历史累计有螺面积共 14.10 万 hm2, 其中 88.08% 于 1950–1979 年首次发现; 共消 灭 11.45 万 hm2 有螺面积, 77.17% 的历史有螺环境在 1970–1999 年消灭。截至 2016 年, 全省现有螺环境 4 830 个, 其中曾 为感染性钉螺环境 1 051 个; 78.12% 的现有螺环境已存在 40 年以上, 65.75% 的感染性钉螺环境在 10 年内消除了感染性 钉螺。安徽省现有螺环境活螺密度存在空间自相关 (Moran’s I = 0.196, Z = 139.63, P < 0.001); 局部热点分析显示有螺 环境活螺密度在空间上呈聚集性, 长江以南呈高值聚集, 长江以北呈低值聚集; 21 个具有统计学意义的活螺密度高值聚 集区分布于长江沿线及支流水系。时空扫描分析发现现有螺环境中感染性钉螺在 4 处区域存在时空聚集性。结论 安 徽省现有螺环境存在时间长久, 仅靠药物难以消灭, 必须结合环改灭螺。现有螺环境的活螺密度存在空间聚集性, 部分 聚集区也是近年的高风险区域。时空扫描分析发现的历史上感染性钉螺聚集分布的区域中, 部分环境流行因素和人畜 感染的风险仍然存在, 还需将其作为重点防控区域。.
Keywords: Anhui Province; Oncomelania hupensis; Spatial autocorrelation; Spatio-temporal analysis.