Andrus, Peter S.
(2023)
An exploration of gastropod-borne parasites with a focus on intestinal schistosomiasis in Biomphalaria snails inhabiting the Great African Lakes.
PhD thesis, University of Nottingham.
Abstract
Gastropod-borne parasitic diseases are a significant concern for public health all over the world, but particularly in developing countries. Many species of terrestrial and freshwater gastropods serve as the intermediate host for various parasites with medical and/or veterinary significance. One such example is the intravascular trematode species, Schistosoma mansoni (Digenea: Schistosomatidae), which is the leading cause of intestinal schistosomiasis globally. The obligatory intermediate host of S. mansoni is the freshwater snail genus, Biomphalaria (Gastropoda: Planorbidae). The vast majority of intestinal schistosomiasis cases occur in sub-Saharan regions of Africa, with countries in East Africa suffering from a high prevalence of S. mansoni in and around the Great African Lakes. The hyper-endemic nature of intestinal schistosomiasis at Lake Albert and Lake Victoria is a significant public health concern.
In addition to trematodes, other gastropod-borne parasites such aslungworms (Strongylida) are common causes of disease in humans and companion animals. Unlike digenetic trematodes, lungworms do not specialise in their choice of obligatory intermediate host and can use numerous species of both terrestrial and freshwater gastropods to infect their definitive host, typically through consumption. The parasitic nematode genus, Angiostrongylus(Chromadorea: Angiostrongylidae) for example, contains species that cause angiostrongyliasis in humans (An. cantonensis) and dogs (An. vasorum). Despite being endemic to tropical regions, an An. cantonensis infection was recently reported in France as the first ever autochthonous human case of angiostrongyliasis in mainland Europe. Conversely, An. vasorum is found globally. In the UK, it is most prevalent in Southern England and Southern Wales, though there have been reports of the parasite as far north as Scotland.
Chapter 3 “Comparing shell size and shape with canonical variate analysis of sympatric Biomphalaria species within Lake Albert and Lake Victoria” utilises landmark-based geometric morphometric techniques to differentiate the conchological characteristics of four Biomphalaria species inhabiting the Great African Lakes of Uganda. The study found that it was possible to accurately discriminate and identify all Biomphalaria species present at the Great African Lakes in Uganda (B. choanomphala, B. pfeifferi, B. stanleyi and B. sudanica) using a canonical variate analysis (CVA) of the apical and apertural angles of the shell.
Chapter 4 “Schistosoma mansoni infection in Biomphalaria snails at the Ugandan shorelines of Lake Albert and Lake Victoria” uses PCR-based molecular infection detection methods to quantify the prevalence of S. mansoni infection among the Biomphalaria species present at the Ugandan shorelines of Lake Albert (B. pfeifferi, B. stanleyi and B. sudanica) and Lake Victoria (B. choanomphala). It also measures prevalence of infection for each of the wet and dry seasons over a two year period for both lakes. The study found that the mean prevalence of S. mansoni infection was higher at Lake Albert (12.5%) than Lake Victoria (5%), with B. stanleyi (15%) having the highest mean infection prevalence of the four species tested. In addition, the wet seasons at both lakes had a higher mean prevalence of infection than the dry seasons, though this difference was not statistically significant.
Chapter 5 “Schistosoma mansoni infection and population genetic structure of Biomphalaria choanomphala snails in Lake Victoria” uses PCR-based molecular infection detection methods to quantify the prevalence of S. mansoni infection across the Kenyan, Tanzanian and Ugandan shorelines of Lake Victoria. Additionally, several abiotic (temperature, pH, physiochemical etc.) and biotic (snail genetic diversity) factors were measured to investigate which factors are involved in schistosomiasis transmission. The study found the mean prevalence of S. mansoni infection among B. choanomphala snails across Lake Victoria was 9.3%, with the Tanzanian shoreline having the highest prevalence, followed by the Ugandan and Kenyan shorelines. There was a significant positive relationship with infection prevalence and B. choanomphala abundance, calcium, and magnesium concentrations. Conversely, there was a significant negative correlation between infection prevalence and increasing water alkalinity. Lastly, populations of B. choanomphala where S. mansoni infection was present had a higher mean haplotype diversity score and less private haplotypes than populations without infection present.
Chapter 6 “Nematodes and trematodes associated with terrestrial gastropods in Nottingham, England” implements traditional parasitological and molecular identification techniques to survey the terrestrial gastropod populations in and around the city of Nottingham, with the intention of finding medical (or veterinary) important parasites. The study found the mean infection prevalence of terrestrial gastropods was 28.3%, with slugs and snails having similar prevalence of infection. Of the gastropod-borne parasites extracted, seven nematode species and four trematode species were identified. No medical or veterinary important parasites were discovered in or around the city of Nottingham.
| Item Type: |
Thesis (University of Nottingham only)
(PhD)
|
| Supervisors: |
Wade, Chris M.
Davison, Angus |
| Keywords: |
Parasitology; Schistosoma mansoni, Schistosomiasis; Nematodes; Trematodes; Gastropods, Biomphalaria |
| Subjects: |
Q Science > QL Zoology > QL360 Invertebrates |
| Faculties/Schools: |
UK Campuses > Faculty of Medicine and Health Sciences > School of Life Sciences |
| Item ID: |
73788 |
| Depositing User: |
Andrus, Peter
|
| Date Deposited: |
18 Jul 2023 04:40 |
| Last Modified: |
18 Jul 2023 04:40 |
| URI: |
https://eprints.nottingham.ac.uk/id/eprint/73788 |
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