Population Genetics Structure Of Schistosoma Japonicum Among Different Strains

Objective: Schistosomiasis is a zoonotic parasitic disease caused by infection and parasitizing of Schistosoma japonicum, which is severely harmful to human health. About 46 mammal species have been suspected as reservoir hosts for this parasite. In China, S. japonicum still remains a major public health problem. Different degree of genetic variation occurs on the S. japonicum individuals due to geographic isolation and other factors, and gradually turned into many different S. japonicum strains, such as geographical strains, resistant strains and laboratory strains etc, which makes it more difficult for further control and eradication of S. japonicum.Population genetics studies of S. japonicum strains can bring significant contribution to the understanding of its transmission dynamics, host-parasite relationships, clinical symptoms and diagnosis and vaccine development. Therefore, this study we applied microsatellite markers to access population genetics of S. japonicum from a hilly region of Anhui province, compared with a laboratory strain and a marshland strain.Methods: In this study, we performed a multi-locus polymerase chain reaction(PCR) with seven microsatellite markers to amplify 570 S. japonicum cercariae from two parasite populations, one field(Shitai of Anhui province) and one laboratory(Wuxi of Jiangsu province). We also used 13 microsatellite markers to amplify 150 S. japonicum adults from four geographical strains(Hexian, Anqing, Shitai of Anhui province and Wuxi of Jiangsu province). We investigated genetic diversity and Hardy-weinberg equilibrium within strains and each locus with the software FSTAT; population structure with the software Structure; the bottleneck effect(a sharp reduction in population size) of the field population and laboratory population with the software bottleneck; construct the phylogenetic tree of the four strains with software Phylip.Results:1. For the field population and laboratory population:(1)A total of 136 S. japonicum cercariae from the field and 86 from the laboratory, which were genetically unique within single snails, were analyzed;(2)The results showed the bigger numbers of alleles and allelic richness in the field parasite population than in the laboratory;(3)The bottleneck effect was detected in the laboratory population;(4)When two parasite populations were combined, there was a very clear distinction between both isolates using the software Structure.2. For the four geographical strains:(1) The Hexian population show the lowest degree of genetic variation; F-statistic indicated that the genetic differentiation among populations was 30.7%(>25%); pairwise Rst show the nearest relationship between Shitai population and Anqing population, and the farthest between Shitai and Wuxi;(2) Wuxi population was clustered into a single category, so was Hexian. And Shitai population and Anqing population were clustered into a category with the software Structure.(3) In constructing the phylogenetic tree, Wuxi populaion was clustered into a single category, and others were clustered into a category.Conclusion:1. The parasites from the laboratory may not represent the natural population of parasites for studies of preventative measures, drug tolerance or vaccines etc;2. The observed genetic difference between two isolates in this study could possibly be attributed to the differential geographical locations or reservoir hosts they originated.3. The population genetic structure of S.japonicum is related with its geography and environmental.