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In recent decades, numerous studies have sought to better understand the mechanisms underlying the compatibility between Biomphalaria glabrata and Schistosoma mansoni. The developments of comparative transcriptomics, comparative genomics, interactomics and more targeted approaches have enabled researchers to identify a series of candidate genes. However, no molecular comparative work has yet been performed on multiple populations displaying different levels of compatibility. Here, we seek to fill this gap in the literature. We focused on B. glabrata FREPs and S. mansoni SmPoMucs, which were previously demonstrated to be involved in snail/schistosome compatibility. We studied the expression and polymorphisms of these factors in combinations of snail and schistosome isolates that display different levels of compatibility. We found that the polymorphism and expression levels of FREPs and SmPoMucs could be linked to the compatibility level of S. mansoni. These data and our complementary results obtained by RNA-seq of samples from various snail strains indicate that the mechanism of compatibility is much more complex than previously thought, and that it is likely to be highly variable within and between populations. This complexity must be taken into account if we hope to identify the molecular pathways that are most likely to be good targets for strategies aimed at blocking transmission of the parasite through the snail intermediate host., Author summary Schistosomiasis is the second most widespread human tropical parasitic disease after malaria. It is caused by flatworms of the genus Schistosoma, and poses a considerable threat for human health in numerous Asian, African and South American countries. The World Health Organization has set the goal of eradicating schistosomiasis by 2025. However, no vaccine is available, and we currently have only one drug (praziquantel) that can effectively and efficiently treat the disease. As treatment by mass drug administration would enhance the risk of drug resistance in schistosome parasites, complementary strategies to fight this parasitic disease are urgently needed. Freshwater snails of the Biomphalaria genus act as intermediate hosts in the transmission of the schistosome species. Thus, learning more about the mechanisms of the interaction between these snails and the schistosomes could critically facilitate the identification of potential new candidate molecules that may be targeted to prevent schistosome transmission in the field.

Additional file 4. Primers used in this study.

Additional file 1. Infection success after sporocyst transfer. SmBRE sporocysts succeed to infect the two strains of mollusks BgBRE and BgGUA and the vertebrate host.

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International audience; Schistosomiasis is the second most widespread tropical parasitic disease after malaria. To achieve the objective of schistosomiasis eradication in a decade, various research strategies and treatment programs were recommended and supported by WHO. One of these applicable approaches is based on the control of snail vectors in endemic area. Previous field studies have shown that competitor or predator introduction could be effective but no systemic investigation has ever been conducted to identify snail microbial pathogen and evaluate its molluscicide effect.In this work, our aim is to provide a characterization of a novel infectious agent isolated from unhealthy Biomphalaria snails in our laboratory.

International audience; Les modifications épigénétiques sont transmises au cours des générations, cependant le mode de transmission est inconnu pour la plupart des organismes. Notre objectif c’est de comprendre l’implication des modifications épigénétiques dans le succès du parasite, et de déterminer ainsi leur héritabilité (mendélienne ou non-mendélienne) dans le modèle Schistososma mansoni avec son hôte intermédiaire Biomphalaria glabrata. Dans ce but, nous avons effectué des croisements entre deux isolats géographiques différents de Schistosoma mansoni. Le phénotype des hybrides de trois générations successives a été analysé au niveau des traits de vie, mais aussi au niveau moléculaire. Pour cela, nous avons focalisé sur une famille multigénique (SmPoMucs : Schistosoma mansoni Polymorphic Mucins), qui est essentielle pour le succès d’infestation du parasite et qui son expression est contrôlée par des marques épigénétiques. Nos résultats préliminaires suggèrent que la structure de la chromatine au niveau de ces gènes candidats est transmise plutôt d’une façon non-mendélienne. Nous espérons contribuer par ce travail à une meilleure compréhension des origines de la forte adaptation du parasite sur ses hôtes, dans le but de lutter contre cette maladie

International audience; Historically, the prevailing view in the field of invertebrate immunity was that invertebrates that do not possess acquired adaptive immunity rely on innate mechanisms with low specificity and no memory. Several recent studies have shaken this paradigm and suggested that the immune defenses of invertebrates are more complex and specific than previously thought. Mounting evidence has shown that at least some invertebrates (mainly Ecdysozoa) show high levels of specificity in their immune responses to different pathogens, and that subsequent reexposure may result in enhanced protection (recently called 'immune priming'). Here, we investigated immune priming in the Lophotrochozoan snail species Biomphalaria glabrata, following infection by the trematode pathogen Schistosoma mansoni. We confirmed that snails were protected against a secondary homologous infection whatever the host strain. We then investigated how immune priming occurs and the level of specificity of B. glabrata immune priming. In this report we confirmed that immune priming exists and we identified a genotype-dependent immune priming in the fresh-water snail B. glabrata.

International audience; Objectives To optimize host-to-host transmission, digenean trematodes (parasites) synchronize their cercarial emission patterns with the aquatic activities of their vertebrate hosts. Schistosoma mansoni has a strictly diurnal shedding pattern involving two circadian chronotypes: an early shedding pattern with a mean peak occurring at 11:00 h and a late pattern with a mean peak occurring at 16:00 h. We analysed the cercarial emergence pattern of three schistosome populations from Oman where S. mansoni is resurgent. Methods For each schistosome population, the cercarial emergence pattern was assessed hourly over several days. Because we identified a new chronotype hitherto unknown in S. mansoni, we undertook taxonomic characterization based on egg morphology and mitochondrial DNA sequence (COX1). Results Taxonomic characterization revealed that the three schistosome populations belong to the species S. mansoni. Hence, this is the first report of this species exhibiting a nocturnal chronotype, with the mean peak occurring at 20:00 h. We interpreted the new chronotype as being the result of a lateral transfer of S. mansoni from humans to Rattus rattus. Conclusion The cercarial emergence pattern of S. mansoni from Oman is circadian, exhibiting either a diurnal or a nocturnal phenotype.

La Bilharziose intestinale se manifeste chez l'homme environ 3 mois après l'infestation, par de la fièvre et des troubles intestinaux; la diarrhée étant au premier plan associée à des douleurs rectales ou à type de crises de colique. L'évolution de l'atteinte intestinale est en générale favorable (même sans traitement) mais des complications chroniques peuvent survenir dont en particulier une dégénérescence hépatique (cirrhose) accompagnée d'une hypertension portale. L'état général du malade s'altère au fil des années et le pronostic de la bilharziose hépatosplénique est réservé

In the past few years, the development of molecular systematic methods in phylogenetic studies has considerably increased our knowledge of the historical biogeography of schistosomes (Trematoda : Schistosomatidae) and some of their intermediate snail hosts across the continents. Concomitantly, at a more restricted geographic scale, host and parasite population structures have been characterized, using neutral molecular markers, providing an improved understanding of coevolutionary dynamics between hosts and parasites and their epidemiological implications. Finally, at a microspatial scale, analyses of the genotypic composition of parasite infrapopulation, within both definitive and intermediate hosts, have provided useful information on transmission and recruitment processes in the field. Based on recent published studies, we will review (i) phylogeographical hypotheses for the origin and radiation of Schistosoma in Asia, India, Africa, and South America, (ii) new Schistosoma species recently described, (iii) coevolutionary processes acting in fragmented population, (iv) local patterns by which hosts may acquire schistosome infection and factors which are likely to enhance diversity, providing opportunities for parasite adaptation to host and/or environmental changes

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