日本血吸虫雌雄异体，其生活史各阶段均有雌雄之分，人畜等终宿主只有既感染雌性尾蚴又感染雄性尾蚴后，雌雄性童虫于宿主体内合抱后，雌虫才能发育成熟、产卵，完成生活史。血吸虫以单性个体形式感染宿主是其基本生物学特征，但是仅感染雌性尾蚴或仅感染雄性尾蚴的终宿主，因体内无虫卵产生而无症状、不被常用方法检出和传统观点认为单性（尤其是雌性）血吸虫不能长期存活而一直被忽视。我们近期研究认为感染单性血吸虫的终宿主普遍存在，并且终宿主体内单性血吸虫可长期存活。基于上述认知，我们提出假说：终宿主体内长期存活的单性血吸虫在疾病流行和种群演化中有着重要作用，单性感染者是被忽视重要潜在传染源。围绕此假说，本课题拟采用动物实验、现场调查和群体遗传学方法：探索终宿主体内长期寄生的单性血吸虫的生殖潜能、对药物吡喹酮敏感性及其遗传特征；揭示单性血吸虫感染对区域性疾病流行和血吸虫种群结构的影响。结果将为全球消除血吸虫病提供参考。

Schistosoma japonicum is dioecious. At each stage of its life cycle, the parasites are divided into males and females. Only when a final host (i.e. humans, livestock, or wildlife) is infected with both male and female schistosome cercariae, can the parasites within the host develop, mature and mate with an opposite sex, and then paired females can produce eggs, finally completing the life cycle of the parasite. It is a fundamental biological trait that S. japonicum infects a final host in the form of single schistosome individuals. However, a final host infected with single-sex schistosome is asymptomatic due to the production of no eggs within the host body and is also not detected by common diagnostic methods. Moreover, there is a traditional viewpoint that single-sex schistosome (especially females) are not able to live for a long time within a final host. All the above have resulted in that single-sex schistosome infections in final hosts have long been neglected. One of our recent studies suggested, however, that the number of final hosts infected with single-sex schistosome is huge in nature, and within a final host single-sex schistosome can survive over a long time. Based on the above evidence, we here proposed the hypothesis that the long-term survival of single-sex S. japonicum within a final host is of great importance in the transmission and evolution of the parasite species, and a final host infected with single-sex schistosome can serve as an important potential reservoir for S. japonicum. Under this hypothesis, the purposes of this project are, by using animal experiments, field surveys and population genetics, to explore the reproductive potential and the sensitivity to the drug praziquantel of the single-sex schistosome who have survived over a long time within a final host; and to reveal the genetics of the reproductive potential and drug resistance of the single-sex schistosome and their impact on transmission and population genetics of S. japonicum in a local endemic area. The results from this project would provide great information for realizing the target of the global eradication of schistosomiasis.