Molecular approaches to improve understanding of the distribution of human-infecting Schistosoma species

Abstract

It is estimated that over 200 million people are at risk from schistosomiasis, a Neglected Tropical Disease caused by Schistosoma trematode parasites that has significant health and socioeconomic consequences. To enable the successful control and eradication of this disease, it is crucial to develop and employ accurate diagnostics of Schistosoma trematodes in the natural environment. The overarching aims of the work for this thesis were i) to assess the potential of environmental DNA (eDNA)-based approaches to assess the distribution and abundance of schistosomes, and ii) to investigate the utility of eDNA to enable a broader understanding of the ecology of the freshwater communities where schistosomes are found. Environmental DNA-based tests for the human-infecting schistosomes S. mansoni and S. haematobium are reported. These are shown to exhibit a high-level of species specificity, especially the S. mansoni assay, and shown to be capable of detecting schistosomes in natural freshwater environments. A novel eDNA xenomonitoring approach to detect the schistosome infection in intermediate host snails is reported. The results correspond strongly with those obtained from direct tests of snails infection status from molecular analyses of their tissue samples, suggesting eDNA-based xenomonitoring could be a powerful surveillance tool for assessing infection status of host snail populations. A metabarcoding study of biological diversity within African freshwaters is reported. The results highlight the potential of eDNA metabarcoding for the characterization of metazoan communities from different habitats, but clearly demonstrate the need for very high levels of sequence read coverage and/or taxon-specific primers to more fully describe
the biological communities present. Overall, the results presented support the concept that eDNAbased approaches are useful for monitoring schistosome presence in endemic freshwaters, potentially enabling enhanced detection of schistosomiasis infection risk, and evaluating the success of interventions to control and eliminate this disease.

Date of Award	23 Jun 2020
Original language	English
Awarding Institution	The University of Bristol
Supervisor	Martin J Genner (Supervisor) & Eric R Morgan (Supervisor)