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Genetic and phenotypic variations of Trichomonas SPP in humans

Squire, Daniel (2018) Genetic and phenotypic variations of Trichomonas SPP in humans. PhD thesis, Murdoch University.

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Population genetic studies of Trichomonas vaginalis have detected high genetic diversity associated with phenotypic differences in clinical presentations. In this study, microscopy and multi-locus sequence typing (MLST) were used to identify and genetically characterise T. vaginalis isolates from patients in Australia and Ghana. Epidemiological data were also obtained from the Ghanaian population. Of 479 women recruited from Ghana, 63 (13.2%; 95% CI 9.5-17.6) and 78 (16.8%; 95% CI 12.2-21.1) had T. vaginalis based on microscopy and PCR respectively. Regional prevalence of T. vaginalis infection was 21.7% (95% CI 17.1-26.9%) and 12.8% (95% CI 8.6-18.3%) for Volta and Greater Accra regions respectively. There was a significant difference in prevalence between the two regions (Fisher exact test, P =0.013). Trichomonas vaginalis infection was significantly associated with vaginal itch (OR = 1.38, P = 0.04), a prior history of stillbirth (OR = 3.62, P = 0.04) and participation in oral sex (OR = 1.10, P = 0.04). There were no significant associations between genotypes at any locus and clinical presentation score. Seventy-one polymorphic nucleotide sites, 36 different alleles, 48 sequence types, 24 of which were novel, were identified among 178 isolates, revealing a geneticallly diverse T. vaginalis population. Polymorphism was found at most loci among both Australian and Ghanaian isolates, although there was some variation between countries. The number of alleles for each locus ranged from two to nine. Study results confirmed geographic expansion and diversity of the T. vaginalis population. Two-type population were identified in this study. Linkage disequilibrium was observed, suggesting that the T. vaginalis population is highly clonal. Multillocus disequilibrium was observed even when analysing clades separately, as well as widespread clonal genotypes, suggesting that there is no evidence of recent recombination. The potential impact of genetic diversity on varied pathology observed among T. vaginalis infected individuals requires further research. Ethical clearance for this study was granted by the Ethics and Review Committee of Murdoch University and the Human Ethics Committee of the Ghana Health Service.

Item Type: Thesis (PhD)
Supervisor(s): Thompson, Andrew, Lymbery, Alan and Walters, Jennifer
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