Transmission of Schistosomes : Scaling up the competence concept to the ecosystem level

International audienc

Gut microbiota diversity according to dietary habits and geographical provenance

The gut microbiota is an ecosystem including all bacterial species that permanently colonize the gastro intestinal tract and a large number of other microorganisms from the environment. These millions of microorganisms may be unbalanced by a number of external and internal factors. The aim of this review is to summarize recent findings on animal and human studies on the effect of dietary and geographical provenance on gut microbiota-composition. It includes results on the influence of dietary products, type of diet (e.g. vegetarian and omnivorous subgroups), and geographic areas, as well as differences between populations within the same area. In animal models, most results showed contradictory effects on modulation of the intestinal microbiota within the same phylum, while in human studies, dietary products, such as fat, are often reported as being associated with an increase in Bacteroidetes and Actinobacteria species and a decrease in those in the Firmicutes and Proteobacteria phylum. The results of different studies showed that the omnivorous group has a higher diversity of bacteria compared to vegetarians. Gut microbiota composition differs widely between different areas and between different ethnic groups within the same area. However, a higher diversity of bacteria species was encountered in the African population. The conclusions highlight that gut microbiota composition differs according to diet and eating habits which are closely correlated to geographical location suggesting therefore, the need for more in-depth research, looking at ethnic diversity and eating habits. Keywords: Gut microbiota, Diversity, Diet, Dietary patterns, Geographical area

Development of environmental loop-mediated isothermal amplification (eLAMP) diagnostic tool for Bulinus truncatus field detection

International audienceBackground Global changes are reshaping the distribution of vector-borne diseases by spreading vectors to previously non-endemic areas. Since 2013, urogenital schistosomiasis has emerged in Corsica and threatens European countries. Gastropod vectors release schistosome larvae that can infect humans who come into contact with freshwater bodies. Monitoring schistosomiasis host vectors is a prerequisite to understand and subsequently to control this pathogen transmission. Because malacological surveys are time consuming and require special expertise, the use of a simple molecular method is desirable. Methods The aim of this study is to develop a ready-to-use protocol using the LAMP (loop-mediated isothermal amplification) method to detect environmental DNA of Bulinus truncatus , vector of Schistosoma haematobium . Interestingly, LAMP method possesses all the characteristics required for adaptability to field conditions particularly in low-income countries: speed, simplicity, lyophilized reagents, low cost and robustness against DNA amplification inhibitors. We have tested this new method on Corsican water samples previously analysed by qPCR and ddPCR. Results We demonstrate that our diagnostic tool B. truncatus eLAMP (Bt-eLAMP) can detect the eDNA of Bulinus truncatus as effectively as the two other methods. Bt-eLAMP can even detect 1/4 of positive samples not detectable by qPCR. Moreover, the complete Bt-eLAMP protocol (sampling, sample pre-process, amplification and revelation) does not require sophisticated equipment and can be done in 1 ½ h. Conclusions LAMP detection of environmental DNA provides large-scale sensitive surveillance of urogenital schistosomiasis possible by identifying potentially threatened areas. More generally, eLAMP method has great potential in vector-borne diseases and ecology. Graphical Abstrac

Development of environmental loop-mediated isothermal amplification (eLAMP) diagnostic tool for Bulinus truncatus field detection

Background Global changes are reshaping the distribution of vector-borne diseases by spreading vectors to previously non-endemic areas. Since 2013, urogenital schistosomiasis has emerged in Corsica and threatens European countries. Gastropod vectors release schistosome larvae that can infect humans who come into contact with freshwater bodies. Monitoring schistosomiasis host vectors is a prerequisite to understand and subsequently to control this pathogen transmission. Because malacological surveys are time consuming and require special expertise, the use of a simple molecular method is desirable. Methods The aim of this study is to develop a ready-to-use protocol using the LAMP (loop-mediated isothermal amplification) method to detect environmental DNA of Bulinus truncatus, vector of Schistosoma haematobium. Interestingly, LAMP method possesses all the characteristics required for adaptability to field conditions particularly in low-income countries: speed, simplicity, lyophilized reagents, low cost and robustness against DNA amplification inhibitors. We have tested this new method on Corsican water samples previously analysed by qPCR and ddPCR. Results We demonstrate that our diagnostic tool B. truncatus eLAMP (Bt-eLAMP) can detect the eDNA of Bulinus truncatus as effectively as the two other methods. Bt-eLAMP can even detect 1/4 of positive samples not detectable by qPCR. Moreover, the complete Bt-eLAMP protocol (sampling, sample pre-process, amplification and revelation) does not require sophisticated equipment and can be done in 1 ½ h. Conclusions LAMP detection of environmental DNA provides large-scale sensitive surveillance of urogenital schistosomiasis possible by identifying potentially threatened areas. More generally, eLAMP method has great potential in vector-borne diseases and ecology

Molecular characterization of schistosome cercariae and their Bulinus snail hosts from Niakhar, a seasonal transmission focus in central Senegal

International audienceBulinus senegalensis and Bulinus umbilicatus, two sympatric freshwater snails found in temporal ponds in Senegal, were thought to be involved in the transmission of Schistosoma haematobium and/or Schistosoma curassoni. To better understand the role of these Bulinus species in the transmission of human and animal Schistosoma species, B. senegalensis and B. umbilicatus were collected in 2015, during a malacological survey, from a temporal pond in Niakhar, central Senegal. Snails were induced to shed cercariae on two consecutive days. Individual cercariae from each snail were collected and preserved for molecular identification. Infected snails were identified by analysis of a partial region of the cytochrome c oxidase subunit 1 (cox1) gene. Six individual cercariae shed from each infected snail were identified by analyses of the cox1, nuclear ITS and partial 18S rDNA regions. Of the 98 snails collected, one B. senegalensis had a mixed infection shedding S. haematobium, S. bovis and S. haematobium-S. bovis hybrid cercariae and one B. umbilicatus was found to be shedding only S. haematobium. These data provide molecular confirmation for B. senegalensis transmitting S. bovis and S. haematobium-S. bovis hybrids in Senegal. The multiple Bulinus species involved in the human urogenital schistosomiasis in Senegal provides a high force of transmission warranting detailed mapping, surveillance and regular treatment of at-risk populations

Phylogeny of seven Bulinus species originating from endemic areas in three African countries, in relation to the human blood fluke Schistosoma haematobium.

International audienceBackgroundSnails species belonging to the genus Bulinus (Planorbidae) serve as intermediate host for flukes belonging to the genus Schistosoma (Digenea, Platyhelminthes). Despite its importance in the transmission of these parasites, the evolutionary history of this genus is still obscure. In the present study, we used the partial mitochondrial cytochrome oxidase subunit I (cox1) gene, and the nuclear ribosomal ITS, 18S and 28S genes to investigate the haplotype diversity and phylogeny of seven Bulinus species originating from three endemic countries in Africa (Cameroon, Senegal and Egypt).ResultsThe cox1 region showed much more variation than the ribosomal markers within Bulinus sequences. High levels of genetic diversity were detected at all loci in the seven studied species, with clear segregation between individuals and appearance of different haplotypes, even within same species from the same locality. Sequences clustered into two lineages; (A) groups Bulinus truncatus, B. tropicus, B. globosus and B. umbilicatus; while (B) groups B. forskalii, B. senegalensis and B. camerunensis. Interesting patterns emerge regarding schistosome susceptibility: Bulinus species with lower genetic diversity are predicted to have higher infection prevalence than those with greater diversity in host susceptibility.ConclusionThe results reported in this study are very important since a detailed understanding of the population genetic structure of Bulinus is essential to understand the epidemiology of many schistosome parasites

18S-sequences

This file covers all the 18S sequences for six Bulinus species (B. truncatus, B. tropicus, B. globosus, B. umbilicatus, B. senegalensis, and B. forskalii) collected from three African counties (Cameroon, Senegal and Egypt). They were sequenced using an ABI Prism BigDye® Terminator v1.1 Cycle Sequencing Ready Reaction Kit (PE, Applied Biosystems), and were aligned using ClustalX in Mega6

Data from: Phylogeny of seven Bulinus species originating from endemic areas in three African countries, in relation to the human blood fluke Schistosoma haematobium

Background: Snails species belonging to the genus Bulinus (Planorbidae) serve as intermediate host for flukes belonging to the genus Schistosoma (Digenea, Platyhelminthes). Despite its importance in the transmission of these parasites, the evolutionary history of this genus is still obscure. In the present study, we used the partial mitochondrial cytochrome oxidase subunit I (cox1) gene, and the nuclear ribosomal ITS, 18S and 28S genes to investigate the haplotype diversity and phylogeny of seven Bulinus species originating from three endemic countries in Africa (Cameroon, Senegal and Egypt). Results: The cox1 region showed much more variation than the ribosomal markers within Bulinus sequences. High levels of genetic diversity were detected at all loci in the seven studied species, with clear segregation between individuals and appearance of different haplotypes, even within same species from the same locality. Sequences clustered into two lineages; (A) groups Bulinus truncatus, B. tropicus, B. globosus and B. umbilicatus; while (B) groups B. forskalii, B. senegalensis and B. camerunensis. Interesting patterns emerge regarding schistosome susceptibility: Bulinus species with lower genetic diversity are predicted to have higher infection prevalence than those with greater diversity in host susceptibility. Conclusion: The results reported in this study are very important since a detailed understanding of the population genetic structure of Bulinus is essential to understand the epidemiology of many schistosome parasites