Genetic diversity and evolution within the genus Bulinus and species-level interactions with the transmission of Schistosoma haematobium group parasites

Pennance, Thomas 2020. Genetic diversity and evolution within the genus Bulinus and species-level interactions with the transmission of Schistosoma haematobium group parasites. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

Schistosomiasis is a Neglected Tropical Disease (NTD) prevalent across much of Africa, and also regions in South America, Asia, the Middle East and parts of Southern Europe. Caused by infections with dioecious parasitic flatworms of the Schistosoma genus, schistosomiasis results in an undue degree of suffering for humans and animals, particularly in Sub-Sharan Africa. Transmission occurs in freshwater containing specific intermediate host snails that act as vectors for the parasites; hosts becoming infected when the larval stages, released (shed) from the snails, burrow through the skin of the mammalian hosts that come into contact with the freshwater. Therefore, in humans this is a preventable water borne disease disproportionately affecting those that do not have access to safe water sources and good sanitation infrastructures. Mass drug administration (MDA) for the control of human schistosomiasis, which can occur in both intestinal and urogenital forms, is the recommended strategy by the World Health Organization (WHO), however, various factors contribute to the maintenance of schistosomiasis transmission in endemic areas of Africa. Potentially the biggest cause for persistence is the reservoir of infection that remains in freshwater intermediate host snails. Establishing the geographical distribution of intermediate host species in endemic regions and determining their associations with different schistosome species is paramount during schistosomiasis control programmes. Following years of neglect, a resurgence of interest in snail focussed surveillance and control is currently underway, with the WHO even recognising it as a critical action point in their 2020 road map for schistosomiasis control and elimination goals by 2030. However, rigorously tested and refined tools necessary for incorporating snails into schistosomiasis control programmes and the fundamental knowledge about the diversity of the snails and schistosomes underpinning such developments, are not available. Focusing on two endemic regions for urogenital schistosomiasis: the Niger River Valley, and the elimination setting of the Zanzibar Archipelago, this study provides new insights into the genetic diversity of Bulinus spp. and importantly, the associations they have with multiple S. haematobium group species in these regions. Furthermore, the first largescale approach for snail surveillance protocols are tested, showing the advantages that this approach will provide in certifying future elimination and in monitoring disease endemicity. Additionally, novel mitogenome data produced for Bulinus spp. from across Sub-Saharan Africa and the Indian Ocean islands are analysed, which sheds light on the evolutionary radiation of this important genus and the cryptic species diversity that has traditionally confounded taxonomy. The findings can be applied to implement new policies on snail surveillance in schistosomiasis control, whilst also providing a valuable resource for future research investigating the Bulinus genus.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Biosciences
Subjects:	Q Science > Q Science (General)
Date of First Compliant Deposit:	15 October 2020
Last Modified:	16 Oct 2020 10:58
URI:	https://orca.cardiff.ac.uk/id/eprint/135638

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