Assessing the diversity and distribution of potential intermediate hosts snails for urogenital schistosomiasis: Bulinus spp. (Gastropoda: Planorbidae) of Lake Victoria

Abstract

Background The Lake Victoria basin is one of the most persistent hotspots of schistosomiasis in Africa, the intestinal form of the disease being studied more often than the urogenital form. Most schistosomiasis studies have been directed to Schistosoma mansoni and their corresponding intermediate snail hosts of the genus Biomphalaria , while neglecting S. haematobium and their intermediate snail hosts of the genus Bulinus . In the present study, we used DNA sequences from part of the cytochrome c oxidase subunit 1 ( cox 1) gene and the internal transcribed spacer 2 (ITS2) region to investigate Bulinus populations obtained from a longitudinal survey in Lake Victoria and neighbouring systems during 2010–2019. Methods Sequences were obtained to (i) determine specimen identities, diversity and phylogenetic positions, (ii) reconstruct phylogeographical affinities, and (iii) determine the population structure to discuss the results and their implications for the transmission and epidemiology of urogenital schistosomiasis in Lake Victoria. Results Phylogenies, species delimitation methods (SDMs) and statistical parsimony networks revealed the presence of two main groups of Bulinus species occurring in Lake Victoria; B. truncatus / B. tropicus complex with three species ( B. truncatus , B. tropicus and Bulinus sp. 1), dominating the lake proper, and a B. africanus group, prevalent in banks and marshes. Although a total of 47 cox 1 haplotypes, were detected within and outside Lake Victoria, there was limited haplotype sharing (only Haplotype 6 was shared between populations from Lake Victoria open waters and neighbouring aquatic systems) – an indication that haplotypes are specific to habitats. Conclusions The Bulinus fauna of Lake Victoria consists of at least B. truncatus , B. tropicus , Bulinus sp. 1 ( B. trigonus ?) and B. ugandae . The occurrence and wide distribution of Bulinus species in Lake Victoria potentially implies the occurrence of urogenital schistosomiasis in communities living along the shores and on islands of the lake who depend solely on the lake for their livelihood. More in-depth studies are needed to obtain a better picture of the extent of the disease in the Lake Victoria basin.

Species composition and diversity of freshwater snails and land snails at the swampy areas and streams edges in the urban zone of Douala, Cameroon

“…Regarding aquatic snails, our results are clearly close to those recorded in five provinces of northwestern Angola where nine genera have been identified using morphological characteristics: Biomphalaria, Bulinus, Gyraulus, Lanistes, Lentorbis, Lymnaea, Melanoides, Physa and Succinea (Allan et al, 2017) (Mbuh and Mbwaye, 2005;Jean-Richard et al, 2014;Aleixo et al, 2015;Isah, 2019). Moreover, the presence of the Planorbidae species Biomphalaria pfeifferi only in the locality of PK10-Plateau transforms this locality into a risk environment for bilharzia (Gryseels, 1985;De Clercq, 1987;Dreyfuss and Rondelaud, 2011;Bridger et al, 2018;Chibwana et al, 2020). According to the reports, the strongly anthropized sites are clearly less rich than the natural sites or sites undergoing regeneration process and anthropogenic disturbance plays a key role in shaping species diversity and community structure of land snail fauna (Douglas et al, 2013).…”

“…The freshwater snails Physidae Physella (Physa) acuta and Planorbidae Biomphalaria pfeifferi are known to be medically important for humans and livestock health since they are obligate intermediate host of distomatosis and schistosomiasis agents, respectively (Dreyfuss and Rondelaud, 2011;Andreazzi et al, 2017;Bridger et al, 2018;d'Ovidio et al, 2019;Chibwana et al, 2020). The low species diversity is associated with low abundance in native snails, resulting in the weak exploitation of resources.…”

“…Otherwise, freshwater snails play the role of obligate intermediate hosts for infectious agents, among which the most frequently cited are cercariae of the digenetic trematodes worms (flukes) belonging to the genus Fasciala and Schistosoma, responsible for human and cattle chronic infection fascioliasis and schistosomiasis respectively (Ntonifor and Ajayi, 2007;Dawet et al, 2012;Adang et al, 2015). Among the snails mentioned there are freshwater species of the genera Biomphalaria, Bulinus, Oncomelania and Planorbarius whose presence in water points (streams, river edges and swamps) is a major risk factor for the spread of bilharzia (Dreyfuss and Rondelaud, 2011;Bridger et al, 2018;Chibwana et al, 2020). Several land snails are crop pests and cause damage in agriculture and horticulture.…”

Mitochondrial genome of Bulinus truncatus (Gastropoda: Lymnaeoidea): Implications for snail systematics and schistosome epidemiology

“…Considerable work ( Stothard et al., 2002 ) has been done in this direction, with a particular focus on defining, assessing and/or using genetic markers in nuclear ribosomal and in mitochondrial (mt) DNAs for specific identification, particularly the second internal transcribed spacer (ITS-2) and cytochrome c oxidase subunit 1 gene ( cox 1), respectively ( Stothard et al., 2002 ; Jorgensen et al., 2013 ). Indeed, mt cox 1 sequences have shown major utility for the identification of species and groups, and to establish the genetic/systematic relationships of species/taxa within the genus Bulinus ( Tumwebaze et al., 2019 ; Chibwana et al., 2020 ), although, in some instances, there has been limited statistical support for some relationships ( Kane et al., 2008 ). The latter finding indicates that the use of a greater number of phylogenetically-informative genetic markers should enhance the taxonomic classification of Bulinus species or subspecies, and could improve the phylogenetic reconstruction of systematic relationships.…”

Morphological and Molecular Characterization of Paragonimus Species Isolated from Freshwater Crabs in Southern Yunnan, China

“…is expands the potential role of DNA sequence analysis to assist in confirming species distribution and phylogenetic diversity. Currently, nuclear (internal transcribed spacer 2 (ITS2) and mitochondrial DNA (cytochrome c oxidase subunit 1 (CO1)) sequences are used for assessing the phylogeographies in various organisms [15,16].…”