An exploration of gastropod-borne parasites with a focus on intestinal schistosomiasis in Biomphalaria snails inhabiting the Great African Lakes

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

An exploration of gastropod-borne parasites with a focus on intestinal schistosomiasis in Biomphalaria snails inhabiting the Great African Lakes

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

Differentiation of Bulinus senegalensis and Bulinus forskalii Snails in West Africa Using Morphometric Analysis

Purpose: Accurate identification of medically important intermediate host and vector species is crucial for understanding disease transmission and control. Identifying Bulinus snails which act as intermediate host species for the transmission of schistosomiasis is typically undertaken using conchological and genital morphology as well as molecular methods. Methods: Here, a landmark-based morphometric analysis of shell morphology was undertaken to determine its utility to distinguish the closely related and morphologically similar sister species Bulinus senegalensis and Bulinus forskalii. The method was developed to increase the accuracy of conchological morphology methods to identify Bulinus species in the field. Both species are found in West Africa, but only B. senegalensis is implicated in the transmission of urogenital schistosomiasis. Results: We found when scaled down to the same length, 3-whorl and 4-whorl (juvenile) B. senegalensis shells had a longer spire, narrower body whorl and shorter aperture than B. forskalii. In contrast, 5-whorl (adult) B. senegalensis had a shorter spire, but still had a shorter aperture and narrower body whorl than B. forskalii. Canonical Variate Analysis (CVA) showed minimal overlap between B. senegalensis and B. forskalii for 3-whorl and 4-whorl shells, with a clear separation for 5-whorl shells. Overall, B. senegalensis had a consistently shorter aperture size and narrower body whorl than B. forskalii for all development stages. Spire length was variable depending on the stage of development, with 3-whorl and 4-whorl shells having the opposite trends of adult shells. Conclusions: Our study demonstrates the applicability of landmark-based morphometrics in distinguishing the medically important, Bulinus senegalensis from its morphologically similar sister species, Bulinus forskalii. We recommend using measurements based on spire length, penultimate whorl length, body whorl width and aperture size to differentiate B. senegalensis and B. forskalii, when used with the appropriate information for each shell’s development stage

Seasonal patterns of Schistosoma mansoni infection within Biomphalaria snails at the Ugandan shorelines of Lake Albert and Lake Victoria

Intestinal schistosomiasis is hyperendemic in many sub-Saharan African countries. In Uganda, it is endemic at both Lake Albert (LA) and Lake Victoria (LV) and caused by S. mansoni that uses Biomphalaria snails as obligatory intermediate snail hosts. To shed light on local patterns of infection, we utilised two PCR-based methods to detect S. mansoni within Biomphalaria spp. as collected at the Ugandan shorelines of Lake Albert and Lake Victoria from 2009–2010. Overall, at our Lake Albert sites, the mean infection prevalence was 12.5% (15 of 120 snails), while at our Lake Victoria sites the prevalence was 5% (3 of 60 snails). At our Lake Albert sites, the highest infection prevalence of 13.3% (8 of 60 snails) was at Walukuba, while at our Lake Victoria sites, the highest infection prevalence of 10% (2 of 20 snails) was at Lwanika. Three species of Biomphalaria, B. pfeifferi, B. stanleyi and B. sudanica, were identified at our Lake Albert collection sites, while only a single species, B. choanomphala, was identified at our Lake Victoria collection sites. Biomphalaria stanleyi (2 of 20 snails; 15%) had the highest infection prevalence, followed by B. sudanica (5 of 60 snails; 13.3%), B. pfeifferi (4 of 40 snails; 10%) and B. choanomphala (3 of 60 snails; 5%). Of the Biomphalaria species identified, B. choanomphala had the highest haplotype (gene) diversity score, followed by B. stanleyi, B. sudanica and B. pfeifferi. Sites with a higher mean prevalence of S. mansoni infection had higher intra-species haplotype diversity scores than sites with a lower mean prevalence. The wet seasons (LA: 13.3%; LV: 8.7%) had a consistently higher mean infection prevalence of S. mansoni than the dry seasons (LA: 9.5%; LV: 5%) for all species and all sites tested at both Lake Albert (n = 480) and Lake Victoria (n = 320), though the difference was not statistically significant

Seasonal patterns of Schistosoma mansoni infection within Biomphalaria snails at the Ugandan shorelines of Lake Albert and Lake Victoria

Intestinal schistosomiasis is hyperendemic in many sub-Saharan African countries. In Uganda, it is endemic at both Lake Albert (LA) and Lake Victoria (LV) and caused by S. mansoni that uses Biomphalaria snails as obligatory intermediate snail hosts. To shed light on local patterns of infection, we utilised two PCR-based methods to detect S. mansoni within Biomphalaria spp. as collected at the Ugandan shorelines of Lake Albert and Lake Victoria from 2009–2010. Overall, at our Lake Albert sites, the mean infection prevalence was 12.5% (15 of 120 snails), while at our Lake Victoria sites the prevalence was 5% (3 of 60 snails). At our Lake Albert sites, the highest infection prevalence of 13.3% (8 of 60 snails) was at Walukuba, while at our Lake Victoria sites, the highest infection prevalence of 10% (2 of 20 snails) was at Lwanika. Three species of Biomphalaria, B. pfeifferi, B. stanleyi and B. sudanica, were identified at our Lake Albert collection sites, while only a single species, B. choanomphala, was identified at our Lake Victoria collection sites. Biomphalaria stanleyi (2 of 20 snails; 15%) had the highest infection prevalence, followed by B. sudanica (5 of 60 snails; 13.3%), B. pfeifferi (4 of 40 snails; 10%) and B. choanomphala (3 of 60 snails; 5%). Of the Biomphalaria species identified, B. choanomphala had the highest haplotype (gene) diversity score, followed by B. stanleyi, B. sudanica and B. pfeifferi. Sites with a higher mean prevalence of S. mansoni infection had higher intra-species haplotype diversity scores than sites with a lower mean prevalence. The wet seasons (LA: 13.3%; LV: 8.7%) had a consistently higher mean infection prevalence of S. mansoni than the dry seasons (LA: 9.5%; LV: 5%) for all species and all sites tested at both Lake Albert (n = 480) and Lake Victoria (n = 320), though the difference was not statistically significant

Phylogenetic insights into the terrestrial snails Helicoidei (Gastropoda: Stylommatophora) with special emphasis on the Camaenidae

The superfamily Helicoidei are a widely distributed and diverse infraorder of land snails and slugs. Here, we constructed a phylogenetic tree based on sequences of the large subunit ribosomal RNA gene to investigate the relationships within the Helicoidei. Based on our phylogenetic tree, the family Camaenidae, as currently recognized, is not monophyletic, with the Polygyridae falling within the group. Likewise, the family Hygromiidae as currently defined is not monophyletic and incorporates the Geomitridae. The family Xanthoncyhidae form a monophyletic group that is sister to the Pleurodontidae. Likewise, the family Helicidae form a monophyletic group; it is sister to the branch incorporating Hygromiidae, Geomitridae, Pleurodontidae, Helicodontidae, and Xanthonychidae. The Solaropsidae are the sister group to a clade comprising other Sagdoidea. Our findings suggest that the Hygromiidae s.l. families should be restored to their previous name, Hygromiidae. A new genus of Bradybaeninae, Jiaoliaous Zhang gen. nov., is described here, with a simple genital system, single dart sac with multi-branched mucous glands, and a penis with a penial sheath

Ears of the Armadillo: Global Health Research and Neglected Diseases in Texas

Neglected tropical diseases (NTDs) have\ud been recently identified as significant public\ud health problems in Texas and elsewhere in\ud the American South. A one-day forum on the\ud landscape of research and development and\ud the hidden burden of NTDs in Texas\ud explored the next steps to coordinate advocacy,\ud public health, and research into a\ud cogent health policy framework for the\ud American NTDs. It also highlighted how\ud U.S.-funded global health research can serve\ud to combat these health disparities in the\ud United States, in addition to benefiting\ud communities abroad

The endogenous and reactive depression subtypes revisited: integrative animal and human studies implicate multiple distinct molecular mechanisms underlying major depressive disorder

Traditional diagnoses of major depressive disorder (MDD) suggested that the presence or absence of stress prior to onset results in either 'reactive' or 'endogenous' subtypes of the disorder, respectively. Several lines of research suggest that the biological underpinnings of 'reactive' or 'endogenous' subtypes may also differ, resulting in differential response to treatment. We investigated this hypothesis by comparing the gene-expression profiles of three animal models of 'reactive' and 'endogenous' depression. We then translated these findings to clinical samples using a human post-mortem mRNA study

Contrasting Biogeographic and Diversification Patterns in Two Mediterranean-Type Ecosystems

The five Mediterranean regions of the world comprise almost 50,000 plant species (ca 20% of the known vascular plants) despite accounting for less than 5% of the world’s land surface. The ecology and evolutionary history of two of these regions, the Cape Floristic Region and the Mediterranean Basin, have been extensively investigated, but there have been few studies aimed at understanding the historical relationships between them. Here, we examine the biogeographic and diversification processes that shaped the evolution of plant diversity in the Cape and the Mediterranean Basin using a large plastid data set for the geophyte family Hyacinthaceae (comprising ca. 25% of the total diversity of the group), a group found mainly throughout Africa and Eurasia. Hyacinthaceae is a predominant group in the Cape and the Mediterranean Basin both in terms of number of species and their morphological and ecological variability. Using state-of-the-art methods in biogeography and diversification, we found that the Old World members of the family originated in sub-Saharan Africa at the Paleocene–Eocene boundary and that the two Mediterranean regions both have high diversification rates, but contrasting biogeographic histories. While the Cape diversity has been greatly influenced by its relationship with sub-Saharan Africa throughout the history of the family, the Mediterranean Basin had no connection with the latter after the onset of the Mediterranean climate in the region and the aridification of the Sahara. The Mediterranean Basin subsequently contributed significantly to the diversity of neighbouring areas, especially Northern Europe and the Middle East, whereas the Cape can be seen as a biogeographical cul-de-sac, with only a few dispersals toward sub-Saharan Africa. The understanding of the evolutionary history of these two important repositories of biodiversity would benefit from the application of the framework developed here to other groups of plants present in the two regions

Limits to reproduction and seed size-number trade-offs that shape forest dominance and future recovery

International audienceThe relationships that control seed production in trees are fundamental to understanding the evolution of forest species and their capacity to recover from increasing losses to drought, fire, and harvest. A synthesis of fecundity data from 714 species worldwide allowed us to examine hypotheses that are central to quantifying reproduction, a foundation for assessing fitness in forest trees. Four major findings emerged. First, seed production is not constrained by a strict trade-off between seed size and numbers. Instead, seed numbers vary over ten orders of magnitude, with species that invest in large seeds producing more seeds than expected from the 1:1 trade-off. Second, gymnosperms have lower seed production than angiosperms, potentially due to their extra investments in protective woody cones. Third, nutrient-demanding species, indicated by high foliar phosphorus concentrations, have low seed production. Finally, sensitivity of individual species to soil fertility varies widely, limiting the response of community seed production to fertility gradients. In combination, these findings can inform models of forest response that need to incorporate reproductive potential