日本血吸虫在不同种类宿主中的种群遗传多样性研究

Schistosoma japonicum, which remains a major public health problem in mainland China, is the only schistosome species for which zoonotic transmission is considered important, with over 40 species of wild and domesticated animals suspected to serve as definitive host reservoirs for the parasite. The multiplicity of potential hosts can affect the population structure of parasite, drive the selective pressure and evolution, furthermore, affect at some degree of differential transmission across host species. In order to characterize the population structure and elucidate transmission patterns of S. japonicum across host species, S. japonicum (including miracidia and adult worm) will be sampled and genotyped using whole genome-wide single nucleotide polymorphism(SNP) markers from a range of naturally infected definitive host species in the Jianghan Plain, Hubei Province, China. Additionally,the epidemilogical survey will be implemented for schistosomiasis among the different definitve hosts. The project's significance is that it will identify the main transmission pattern of S. japonicum among different definitive hosts by genome-wide SNPs, especially between human and other nonhuman definitive hosts.It will not only to assess the population genetic diversification within and among hosts species from infrapopulation to suprapopulation level, but also to gain an understanding of the selective pressures involved in population genetic structure of S. japonicum through hosts. The new insights into these factors will be important for the design of new and more effective schistosomiasis control strategies.In addition, as a multi-host parasite, S.japoniucm provides a theoretically and clinically important model to use in understanding the population biology of multi-host pathogens, which acan affect the evolution and dynamicsof infectious disease to some extent, as well as raise signicant implications for disease control.

日本血吸虫病是我国最严重的人兽共患寄生虫病，主要流行于长江流域的湖北、湖南、江西和安徽等省。日本血吸虫可以感染40余种哺乳动物。病原体在不同宿主间的传播可驱动其对宿主的选择性和种群分化，改变其种群遗传结构，影响疾病的传播模式和防治。然而病原体在多宿主间的种群遗传学研究仍十分匮乏，血吸虫在不同甚至是同一种类终末宿主中的种群遗传结构尚不清楚，严重阻碍了对其在不同宿主间传播模式的认识。本项目拟在湖北省江汉平原，调查人、多种常见家畜及野鼠等自然感染血吸虫的宿主体内的寄生虫负荷；并利用全基因组水平的单核苷酸多态性标记，研究不同种类宿主体内血吸虫的种群遗传差异，揭示不同宿主对血吸虫种群遗传结构的影响，并探讨其在疾病传播中的潜在作用。该项目以日本血吸虫为代表，其研究成果将丰富多宿主寄生虫的种群生物学，而且为制定更有效的血吸虫病防治策略，及研制不同宿主（人/畜）用疫苗提供理论基础和科学依据。

日本血吸虫病是我国最严重的人兽共患寄生虫病，主要流行于长江流域的湖北、湖南、江西和安徽等省。日本血吸虫可以感染40余种哺乳动物。病原体在不同宿主间的传播可驱动其对宿主的选择性和种群分化，改变其种群遗传结构，影响疾病的传播模式。本研究在湖北省江汉平原，对中间宿主钉螺和人、牛、羊、野鼠等多种自然感染血吸虫的终末宿主进行了调查，收集了不同宿主体内的尾蚴、毛蚴和成虫等。并利用多重微卫星PCR扩增及测序，对不同宿主、不同寄生部位和不同发育阶段的日本血吸虫种群的遗传多样性和遗传结构进行了研究。结果显示：中间宿主钉螺体内的尾蚴种群具有高水平的基因型数；钉螺内尾蚴的亲缘关系较近，钉螺间尾蚴的亲缘关系较远；尾蚴在钉螺内的聚集并非随机分布，具有遗传背景的驱动。这种遗传结构既有利于单个钉螺内尾蚴内种群的稳定，又有利于流行区尾蚴种群在整体水平上的遗传多样性。雌、雄虫倾向于与其亲缘关系较远的异性配对，并存在更换伴侣的行为，有助于产生更多基因杂合度更大的后代，以增强其抵御宿主清除和适应环境的能力。血吸虫的遗传变异能够在不同宿主体内得到稳定的传递和延续，这种不同发育阶段、不同寄生部位间的种群遗传结构的稳定性传递可能是随机的。不同宿主享有一定量的私有等位基因，在长期的进化中选择压力仍有可能造成种群的分化，因此，对于不同宿主在血吸虫传播中的地位，仍然值得进一步深入研究，警惕可能的种群分化对血吸虫病传播模式的影响。