Department of Infectious Diseases, Huashan Hospital, State Key Laboratory of Genetic Engineering, Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Ministry of Education Key Laboratory of Contemporary Anthropology, School of Life Sciences, Fudan University, Shanghai, 200438, People's Republic Of China.
Anhui Provincial Institute of Parasitic Diseases, Hefei, 230061, Anhui Province, People's Republic Of China.
Parasit Vectors. 2020 Mar 19;13(1):146. doi: 10.1186/s13071-020-4004-8.
The East Route Project (ERP) of the South-to-North Water Diversion Project (SNWDP) stretches across schistosomiasis endemic and non-endemic areas in China, which may lead to the dispersal of Oncomelania hupensis, the intermediate host of Schistosoma japonicum, from permissive areas along the Yangtze River Basin to non-permissive areas in northern China. A previous survey demonstrated that O. hupensis could survive and breed for 13 years (12 generations) after being transferred to a non-permissive area, and could be infected by S. japonicum. However, it is not clear if the migrated snails will change their ability to transmit S. japonicum.
We infected mice with the cercariae released from the infected transferred snails bred in Jining city of Shandong Province (non-permissive areas) for 13 years. The mice in the control group were infected with cercariae derived from the snails collected in their original habitat (Jiangdu county of Jiangsu Province, permissive areas). Then, we explored the pathogenicity to mice including worm burden, liver egg count and pathology. Additionally, the gene expression profiles of the adult male and female worms recovered from the infected mice were analyzed by RNA sequencing.
The worm burden, liver egg count and pathology of the mice infected with cercariae released from transferred snails bred in non-permissive areas for 13 years showed no significant differences, when compared with the control cercariae. Slight changes occurred at the transcription level between adult male and female worms recovered from mice infected with cercariae derived from snails bred in permissive and non-permissive areas. Only fourteen genes were significantly differentially expressed in the comparison of adult female worms, and no significantly differentially expressed gene was found in the comparison of adult male worms.
Our findings strongly suggest that transferred snails did not change their schistosomiasis transmission ability and the worms derived from them retained the original pathogenicity, even after migrating from permissive to non-permissive areas for 13 years. Therefore, a long-term surveillance system of snails along the SNWDP is urgently needed to prevent the diffusion of O. hupensis and reduce the risk of transmission of schistosomiasis.
南水北调东线工程（ERP）跨越中国血吸虫病流行区和非流行区，这可能导致日本血吸虫中间宿主湖北钉螺从长江流域的许可区扩散到中国北方的非许可区。先前的调查表明，湖北钉螺转移到非许可区后可以存活和繁殖 13 年（12 代），并可被日本血吸虫感染。然而，迁移的钉螺是否会改变其传播日本血吸虫的能力尚不清楚。
我们用在山东省济宁市（非许可区）繁殖 13 年的感染钉螺释放的尾蚴感染小鼠。对照组的小鼠感染从其原栖息地（江苏省江都市，许可区）采集的钉螺感染的尾蚴。然后，我们探索了包括虫荷、肝卵计数和病理学在内的对小鼠的致病性。此外，还通过 RNA 测序分析了从感染小鼠中回收的雌雄成虫的基因表达谱。
与对照组尾蚴相比，用在非许可区繁殖 13 年的转移钉螺释放的尾蚴感染的小鼠的虫荷、肝卵计数和病理学无显著差异。在从感染许可区和非许可区繁殖的钉螺释放的尾蚴感染的小鼠中回收的雌雄成虫之间，转录水平发生了轻微变化。在雌雄成虫的比较中，只有 14 个基因表达显著差异，而在雄虫的比较中没有发现显著差异的基因。
我们的研究结果强烈表明，转移的钉螺并没有改变其血吸虫病传播能力，即使从许可区迁移到非许可区 13 年，从它们身上衍生的蠕虫仍然保留着原有的致病性。因此，迫切需要建立一个沿南水北调东线工程的钉螺长期监测系统，以防止湖北钉螺的扩散，降低血吸虫病传播的风险。
