关键词: 血吸虫病, 钉螺, 监测, 云南省, 传播阻断后

Abstract: Objective　To investigate the distribution characteristics of Oncomelania hupensis snails in Yunnan Province following interruption of schistosomiasis transmission, so as to provide the evidence for assessing the risk of schistosomiasis transmission and scientifically formulating the schistosomiasis surveillance program. Methods　According to the requirements of the National Schistosomiasis Surveillance Scheme (2020 Edition), O. hupensis snail surveillance data were collected from 18 schistosomiasis⁃endemic counties (cities, districts) in Yunnan Province from 2020 to 2024, including area of snail survey, area of snail habitats, area of re⁃emerging snail habitats, number of frames surveyed, number of frames with O. hupensis snails, number of O. hupensis snails captured, and number of living snails, and the occurrence of frames with snails and mean density of living snails were calculated. Changes in snail status over the 5⁃year period from 2020 to 2024 and the differences in snail distributions specified by epidemic intensity, environmental type, and vegetation type were analyzed. Results　The areas of snail survey increased from 1 727.96 hm2 in 2020 to 3 894.45 hm2 in 2024 (peak) across 18 schistosomiasis⁃endemic counties (cities, districts) in Yunnan Province during the period from 2020 through 2024. The areas of snail habitats increased from 70.36 hm2 in 2020 to a peak in 2023 (172.04 hm2), followed by a reduction to 132.36 hm2 in 2024, and the areas of re⁃emerging snail habitats increased from 42.71 hm2 in 2020 to a peak in 2022 (78.43 hm2), followed by a reduction to 40.21 hm2 in 2024. The occurrence of frames with snails and mean density of living snails increased from 1.24% (3 025/244 404) and (0.033 2 ± 0.038 7) snails/0.1 m2 in 2020 to peaks at 2.03% (6 231/307 563) and (0.066 9 ± 0.068 4) snails/0.1 m2 in 2023, followed by reductions to 1.04% (5 829/559 941) and (0.032 6 ± 0.057 7) snails/0.1 m2 in 2024, respectively. There was a significant difference in the occurrence of frames with snails over the 5⁃year study period ([χ2] = 1 962.95, P < 0.05), and the occurrence of frames with snails reduced by 48.71% in 2024 relative to in 2023 ([χ2] = 1 411.05, P < 0.005); however, there was no significant difference in the mean density of living snails over the 5 years (H = 5.310, P > 0.05). There were significant differences in the occurrence of frames with snails ([χ2] = 481.27, P < 0.05) and mean density of living snails (H = 6.872, P < 0.05) in schistosomiasis⁃endemic areas with different epidemic intensities. The occurrence of frames with snails ([χ2] = 25.32 and 38.70, both P values < 0.017) and mean density of living snails (Z = 28.55 and 49.96, both P values < 0.017) were higher in schistosomiasis transmission⁃interrupted and eliminated areas with snails than in schistosomiasis⁃eliminated areas without snails, and the occurrence of frames with snails ([χ2] = 453.54, P < 0.017) and mean density of living snails (Z = -56.97, P < 0.017) were higher in schistosomiasis⁃eliminated areas with snails than in schistosomiasis transmission⁃interrupted areas with snails. O. hupensis snails were mainly distributed in paddy fields, dry farmlands and ditches; however, the occurrence of frames with snails (13.40%, 424/3 164) and mean density of living snails [(0.252 8 ± 0.158 7) snails/0.1 m2] were higher in ponds/weirs than in other types of environments (both P values < 0.05). Rice, dry farmland crops and weeds were main vegetations in which O. hupensis snails were distributed, and the occurrence of frames with snails (2.29%, 7 111/310 140) and mean density of living snails [(0.072 3 ± 0.018 9) snails/0.1 m2] were higher in weeds than in other types of environments (both P values < 0.05). Conclusions　O. hupensis snails have been effectively controlled in Yunnan Province following implementation of integrated schistosomiasis control measures; however, there are still risk factors for schistosomiasis transmission, including reduced attention to schistosomiasis control and snail re⁃emergence. Improved control efforts and surveillance system construction and timely identification of risk factors of snail status and timely management are recommended to ensure the achievement of the target of schistosomiasis elimination as scheduled. 

Key words: Schistosomiasis, Oncomelania hupensis, Surveillance, Yunnan Province, Post?transmission interruption