Population Genetic Analyses Of Schistsoma Japonicum From 2012 To 2015 In A Mountainous Area Of China

Objective: Schistosomiasis japonica is a parasitic disease infected by Schistosoma japonicum,which is severely harmful to human health.The disease is very serious in China,which has been resurging in areas where it was previously well controlled or its transmission interrupted.Different degree of genetic variation occurs in the S.japonicum population due to the factors of geographical isolations or reservoir hosts and so on.At the same time,the bottleneck effect,founder effect and gene flow can cause temporal genetic change of S.japonicum.Genotyping errors can bias the frequencies reported for a population.Even a small per-locus genotyping error rate can result in relatively large probabilities of a multilocus genotype containing at least one error.Therefore,the study assessed the genotyping errors on seven commonly used S.japonicum microsatellites for the parasite families and then conducted the population genetic analyses of S.japonicum from 2012 to 2015 in a mountainous areas(village)of Anhui province to evaluate the efficacy of prevention and control measures and to provide guidance by understanding temporal genetic change of the disease.Methods: The S.japonicum pedigree was established from laboratory crosses of parasites,with adult worm pairs,and their offspring(miracidia,which were stored on Whatman FTA cards)from each parasite family,collected.Each parasite was genotyped in an individual multiplex PCR reaction.Genotyping errors in offspring with the seven microsatellite loci were detected and further estimate with the program CERVUS V3.0.7.We conducted the population genetic analyses of S.japonicum from 2012 to 2015 in the mountainous schistosomiasis endemic areas of central China revealed by microsatellite markers.We calculate indexes of genetic diversity,genetic structure and investigate molecular variance,Hardy-weinberg equilibrium with the software GenAlEx.We study genetic structure with Structure and detect the bottleneck effect by BOTTLENECK.Results:1.The error rate per locus differed among loci,with the highest of 9.8% for sjp22 and the lowest of 0 for sjp4 and sjp18.The mean error rate over loci was 4.3%.The main genotyping error was missing alleles.2.A total of 16 mismatching calls were detected in known mother-offering pairs and 15 in known father-offering pairs.No mistyping was identified for either sjp4 or sjp18.The highest mistyping rate of up to 11.4% in mother-offering and 17.1% in father-offering was estimated for the locus sjp22.The second highest was observed for the locus TS2.3.The average number of alleles in the S.japonicum population from 2012 to 2015 ranged from 7.286 to 12.000,with the lowest in the population of 2015.The population of 2015 for sjp22 conformed to Hardy-weinberg equilibrium,while the rest loci of the population and all loci of other populations showed departure from the equilibrium.4.Wright's Fst between populations was from 0.009(2013 VS 2014)to 0.093(2012 VS 2015).Nei genetic distance was from 0.028(2014 VS 2015)to 0.079(2012 VS 2014).The result of Structure showed the most likely number of genetic clusters could be 4 according to the highest value of ?K.AMOVA analyses indicated that the variance among populations,among individuals and within individuals significant explained 2%,43% and 55% of the observed genetic variation.5.The population of 2015 changed significantly based the infinite allele model(IAM)but not under the two-phased model(TPM).Besides the population of 2015,other populations all appeared normal L-shaped distribution of the allele frequency.Conclusions:1.The loci sjp4 and sjp18 were highly informative for this kind of analyses.2.There were some genotyping errors.However,if the same multiplex reactions are used to compare populations,then the errors should not affect the overall conclusions.3.The overall population size of S.japonicum in the region had a reduction,but not to an extent sufficient to impact significantly on genetic diversity.The reduction of heterogeneity may be relative with temporal gene flow,host-induces selection pressures,the bottleneck effect and the Wahlund effect.4.The genetic variance of S.japonicum populations from 2012 to 2015 was significant difference,which might partly explained by local long-term intensive control measures or repopulation from elsewhere.5.The potential bottleneck effect was revealed in the last year.Samples of S.japonicum in the same areas from the following years should be collected and used to further analysis,which will be valuable for evaluating the efficacy of prevention and control measures and for providing guidance of controlling and eliminating of schistosomiasis.