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Title: Population genetics of Wuchereria bancrofti and its bacterial endosymbiont Wolbachia
Author: Gibbons, Sarah Jane
ISNI:       0000 0001 3496 6418
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2007
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Wuchereria bancrofli is a filarial parasite responsible for 90% of lymphatic filariasis worldwide. Currently a mass drug administration programme, The Global Programme for the Elimination of Lymphatic Filariasis (GPELF) is underway, through the administration of three drugs: diethylcarbamazine (DEC), albendazole and ivermectin, to eliminate lymphatic filariasis as a global he~lth problem. The major aims of the research described in this thesis, were to investigate the genetic diversity of W. bancrofli and their endosymbiotic bacteria Wolbachia and to investigate the presence of putative resistance benzimidazole alleles of W. bancrofli p-tubulin. Attempts were made to isolate W. bancrofli microsatellites using a novel magnetic bead isolation technique. This technique was not successful in identifying microsatellites of w.bancrofli due to overwhelming contamination with human microsatellite DNA. Wolbachia endosymbionts are vertically transmitted and show congruent phylogenies with their nematode hosts, therefore the diversity of W. bancrofli Wolbachia was explored as an indirect marker of w.bancrofli diversity. To investigate the diversity of Wolbachia, genes of the major surface protein (wsp) and cell-division protein (jisZ) were sequenced from W. bancrofli collected from different geographical endemic areas (Burkina Faso, Malawi, Sri Lanka) and were phylogeneticallyanalysed. Although sequence data generated in this study indicates that identical haplotypes of Wolbachia do exist in W. bancrofli samples from different geographical areas, a large amount of diversity was observed in both wsp and flsZ gene sequences in individual W. bancrofli and pooled samples from within these sites. Unweighted Pair Group Method with Arithmetic mean (upGMA) phylogenetic trees generated indicate that Wolbachia is divided into two distinct clades with elevated rates of sequence evolution, especially at non-synonymous sites. Due to the mass drug administration programme currently underway to eliminate lymphatic filariasis, combined with previous reports of benzimidazole resistance (as indicated by Schwab et al. (2006) by the presence of mutation TYR200 in Burkina Faso) experiments to screen for putative resistance benzimidazole alleles in W. bancrofli p-tubulin were investigated. Results demonstrate that the resistanceassociated mutation of benzimidazole at either codon 167 or 200 of the p-tubulin gene was not observed in W. bancrofli samples in patients with varying drug histories from Burkina Faso and Sri Lanka, in contrast to published reports from identical sample sites (village of Tangonko, Burkina Faso). Overall the absence of resistance observed in the study is encouraging for the future of mass drug administration, although further research is required to explain the dynamics of putative resistant alleles under pressure of MDA.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available