Abstract: Objective　To analyze the distribution characteristics of emerging and reemerging Oncomelania hupensis snails after the criteria for transmission control of schistosomiasis were achieved in China, so as to provide insights into assessment of schistosomiasis transmission risk and formulation of snail control strategies during the elimination phase. Methods　O. hupensis survey data in China from 2015 to 2021 were collected from the National Schistosomiasis Pevention and Control Information Management System, and the distribution characteristics of emerging and reemerging O. hupensis snails were descriptively analyzed. Results　Emerging and reemerging O. hupensis snails were identified in China each year from 2015 to 2021, with relatively larger areas with emerging and reemerging O. hupensis snail habitats in 2016 and 2021, and relatively higher numbers of counties (districts) where emerging and reemerging O. hupensis snails were detected in 2016 and 2021. A total of 4 586.30 hm2 of emerging O. hupensis snail habitats were found in 10 schistosomiasis⁃endemic provinces of China (except Fujian and Yunnan Provinces) from 2015 to 2021, with 96.80% in Anhui, Hunan and Hubei provinces, where marshland and lake endemic foci were predominant. A total of 21 023.90 hm2 of reemerging O. hupensis snail habitats were found in 12 schistosomiasis⁃endemic provinces of China from 2015 to 2021, with 97.67% in six provinces of Hubei, Sichuan, Jiangxi, Jiangsu, Yunnan and Anhui, where marshland and lake and hilly endemic regions were predominant. Emerging snail habitats were found in 15.08% of all schistosomiasis⁃endemic counties (districts) in China from 2015 to 2021, and 78.75% of all emerging snail habitats were identified in 11 schistosomiasis⁃endemic counties (districts), with the largest area of emerging snail habitats found in Lixian County, Hunan Province (645.00 hm2). Reemerging snail habitats were found in 47.67% of all schistosomiasis⁃endemic counties (districts) in China from 2015 to 2021, and 43.29% of all reemerging snail habitats were identified in 11 schistosomiasis⁃endemic counties (districts), with the largest area of reemerging snail habitats found in Weishan Li and Hui Autonomous County of Hunan Province (1 579.70 hm2). Conclusions　Emerging and reemerging O. hupensis snails were identified in China each year from 2015 to 2021, with much larger areas of reemerging snail habitats than emerging snail habitats, and larger numbers of schistosomiasis⁃endemic provinces and counties (districts) with reemerging snails were found that those of provinces and counties (districts) with emerging snails. Specific snail control interventions are required tailored to the causes of emerging and reemerging snail habitats. Both emergence and reemergence of O. hupensis snails should be paid attention to in marshland and lake endemic areas, and Guangxi Zhuang Autonomous Region, Shanghai Municipality and Zhejiang Province where schistosomiasis had been eliminated, and reemergence of O. hupensis snails should be given a high priority in hilly areas. In addition, monitoring of O. hupensis snails should be reinforced in snail⁃free areas after flooding.

Key words: Oncomelania hupensis, Emergence, Reemergence, Geographical distribution, China

摘要： 目的　分析我国达到血吸虫病传播控制标准后新发和复现钉螺分布特征，为评估血吸虫病传播风险、制定消除阶段钉螺控制策略提供参考。方法　收集全国血吸虫病防治信息管理系统中2015—2021年全国钉螺调查基本信息，对新发和复现钉螺分布特征进行描述性分析。 结果　2015—2021年，全国每年均有新发和复现钉螺环境报告，其中2016、2021年新发和复现钉螺面积均较高，新发和复现钉螺分布县（市、区）数也以2016、2021年居多。2015—2021年，全国累计新发钉螺面积4 586.30 hm2，分布于除福建省、云南省外的其他10个血吸虫病流行省份，其中96.80%分布于以湖沼型流行区为主的安徽省、湖南省和湖北省；累计复现钉螺面积21 023.90 hm2，12个血吸虫病流行省份均有分布，其中97.67%分布于以湖沼型流行区和山丘型流行区为主的湖北省、四川省、江西省、江苏省、云南省和安徽省。2015—2021年，全国15.08%的血吸虫病流行县（市、区）报告新发钉螺环境，78.75%的新发钉螺面积分布于11个流行县（市、区），其中湖南省澧县累计新发钉螺面积最大（645.00 hm2）；47.67%的流行县（市、区）报告复现钉螺环境，43.29%的复现钉螺面积分布于11个流行县（市、区），其中云南省巍山彝族回族自治县累计复现钉螺面积最大（1 579.70 hm2）。 结论　2015—2021年，全国每年均有新发和复现钉螺环境报告，复现钉螺面积远大于新发钉螺面积，且出现钉螺复现的流行省份数、流行县（市、区）数均高于钉螺新发省份和县（市、区）数。需结合新发和复现钉螺环境形成原因采取相应的钉螺控制措施，湖沼型血吸虫病流行区以及广西壮族自治区、上海市、浙江省等消除省份需同时关注新发和复现钉螺问题，山丘型流行区需重点关注钉螺复现问题。此外，应加强洪涝灾害后无螺区钉螺监测。 　

关键词: 钉螺, 新发, 复现, 地理分布, 中国