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Title: Genetic Diversity, Multiplicity of Infection and Population Structure of Schistosoma Mansoni Isolates of Ethiopia within Human Hosts
???metadata.dc.contributor.*???: Prof. Berhanu Erko
Mulugeta, Aemero
Keywords: Ethiopia;Genetic diversity;Population structure;Microsatellite;Schistosoma mansoni
Issue Date: Oct-2011
Publisher: aau
Abstract: Schistosomiasis is a chronic parasitic disease, affecting over 200 million people and causing over 300,000 deaths per year mainly in sub-Saharan Africa. Strains from the same or different geographical locations have shown differences in egg production, infectivity, pathogenicity and susceptibility to chemotherapy. The objective of this study was to assess the dynamics, genetic polymorphism and structure of Schistosoma mansoni isolates from four endemic foci in Ethiopia. In a cross-sectional study involving 1,073 study participants from Kemissie (10°43'30''N, 039°04'20''E), Wondo Genet (07°05'35''N, 038°36'66''E), Ziway (07°56'37''N, 038°43'25''E), and Sille-Elgo (05°28'39''N, 037°26'02''E), stool specimens were collected and examined for Schistosoma mansoni infection using Kato method. Stool specimens were again collected from 91 positive individuals for molecular studies. The overall prevalence and intensity of Schistosoma mansoni infection from study subjects of Kemissie, Wondo Genet and Ziway was found to be 60.48% and 273 eggs per gram of stool, respectively. Out of 288 miracidia genotyped at a molecular level, 164 unique alleles were counted for all the 11 loci typed from Kemissie (127), Sille-Elgo (102), Wondo Genet (123) and Ziway (94). At a population level, the mean number of alleles per locus, allelic richness, expected heterozygosity in Hardy–Weinberg equilibrium and pairwise FST values ranged from 8.5 to 11.5, 3.46-20.8, 0.66–0.73 and 3.57–13.63%, respectively. The Bayesian structuration showed 67.5-87.3% genetic differentiation of the study populations. The PCA and the Bayesian STRUCTURE had shown four clusters of population. Generally, high level of genetic diversity and population differentiation characterized the S. mansoni isolates of Ethiopia. Genetic diversity and multiplicity of infection with Schistosoma mansoni isolates among and within individual subjects from the four endemic areas of Ethiopia at infrapopulation level also showed a value of 3.09 to 7.55, 1-1.96, 0.59–0.73 and 0.1763–0.4989, mean number of alleles per locus, allelic richness, expected heterozygosity in Hardy–Weinberg equilibrium and FIS, respectively. Mean estimated genetically unique adult worm pairs within hosts ranged from 66-92% revealing the occurrence of infection of a single host with multiple S. mansoni strains. The data also indicated the occurrence of inter- and intra-host genetic variations. Based on previous suggestions about the East African origin of S. mansoni, the present study enabled us to speculate that Ethiopia could be the probable country of origin for xi schistosomes. However, definite conclusion requires further investigation using other genetic markers.
Description: A Dissertation Submitted to the School of Graduate Studies of Addis Ababa University in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Biology (Biomedical Sciences)
Appears in Collections:Thesis - Biology

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