Interactions between Schistosoma haematobium group species and their Bulinus spp. intermediate hosts along the Niger River Valley

Background Urogenital schistosomiasis, caused by infection with Schistosoma haematobium, is endemic in Niger but complicated by the presence of Schistosoma bovis, Schistosoma curassoni and S. haematobium group hybrids along with various Bulinus snail intermediate host species. Establishing the schistosomes and snails involved in transmission aids disease surveillance whilst providing insights into snail-schistosome interactions/compatibilities and biology. Methods Infected Bulinus spp. were collected from 16 villages north and south of the Niamey region, Niger, between 2011 and 2015. From each Bulinus spp., 20–52 cercariae shed were analysed using microsatellite markers and a subset identified using the mitochondrial (mt) cox1 and nuclear ITS1 + 2 and 18S DNA regions. Infected Bulinus spp. were identified using both morphological and molecular analysis (partial mt cox1 region). Results A total of 87 infected Bulinus from 24 sites were found, 29 were molecularly confirmed as B. truncatus, three as B. forskalii and four as B. globosus. The remaining samples were morphologically identified as B. truncatus (n = 49) and B. forskalii (n = 2). The microsatellite analysis of 1124 cercariae revealed 186 cercarial multilocus genotypes (MLGs). Identical cercarial genotypes were frequently (60%) identified from the same snail (clonal populations from a single miracidia); however, several (40%) of the snails had cercariae of different genotypes (2–10 MLG’s) indicating multiple miracidial infections. Fifty-seven of the B. truncatus and all of the B. forskalii and B. globosus were shedding the Bovid schistosome S. bovis. The other B. truncatus were shedding the human schistosomes, S. haematobium (n = 6) and the S. haematobium group hybrids (n = 13). Two B. truncatus had co-infections with S. haematobium and S. haematobium group hybrids whilst no co-infections with S. bovis were observed. Conclusions This study has advanced our understanding of human and bovid schistosomiasis transmission in the Niger River Valley region. Human Schistosoma species/forms (S. haematobium and S. haematobium hybrids) were found transmitted only in five villages whereas those causing veterinary schistosomiasis (S. bovis), were found in most villages. Bulinus truncatus was most abundant, transmitting all Schistosoma species, while the less abundant B. forskalii and B. globosus, only transmitted S. bovis. Our data suggest that species-specific biological traits may exist in relation to co-infections, snail-schistosome compatibility and intramolluscan schistosome development

Étude de la compatibilité de

Schistosoma bovis est le seul Trématode connu pour son aptitude à se développer chez deux Mollusques de genres différents (Bulinus et Planorbarius). Nous avons cherché à évaluer le degré de compatibilité de S. bovis du Soudan et d’Espagne vis-à-vis de B. truncatus de Tunisie et P. metidjensis du Maroc en nous servant d’une part des critères classiquement définis par les auteurs (taux d’infestation des Mollusques, taux de survie post-infestation des Mollusques et durée de la période prépatente), d’autre part en utilisant un critère nouveau, la capacité de pénétration et de développement du miracidium. Nos résultats permettent de conclure que le critère le plus fiable d’appréciation de cette compatibilité est la capacité de pénétration et de développement du miracidium ; c’est en effet lui qui traduit le mieux l’adaptation au sens évolutif du parasite au Mollusque. Ce critère permet par ailleurs de mieux évaluer quantitativement la fraction de la population (miracidiums) potentiellement apte à se développer ou non chez un Mollusque donné. Nous avons pu ainsi déterminer que la meilleure compatibilité Schistosome-Mollusque était réalisée avec les couples S. bovis du Soudan / B. truncatus et S. bovis d’Espagne / P. metidjensis

Évolution des sporocystes de

Les transplantations microchirurgicales de sporocystes fils de Schistosoma bovis chez des Bulinus truncatus sains induisent une dédifférenciation des sporocystes transplantés et leur différenciation en sporocystes sporocystogènes producteurs d’une génération additionnelle de sporocystes fils. Ceux-ci colonisent la glande digestive dans sa totalité et produisent des cercaires infestantes.Durant toute la parasitose une fraction des sporocystes fils issus des sporocystes transplantés persiste dans la zone céphalo-pédieuse et est à son tour le siège d’une sporocystogenèse active. Les données concernant la dynamique de la production cercarienne sont au moins en partie en relation avec la dynamique intramolluscale des populations de sporocystes.Le succès des transplantations microchirurgicales de sporocystes de S. bovis autorise la perspective d’un clonage de cette espèce

Dynamique de la population de Sphaerostoma maius Janiszewska, 1949, Tr\ue9matode parasite du Chevaine (Leuciscus cephalus L.) du cours inf\ue9rieur de la T\ueat (Pyr\ue9n\ue9es-Orientales)

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Activity of praziquantel on in vitro transformed Schistosoma mansoni sporocysts

Praziquantel (PZQ) is effective against all the evolutive phases of Schistosoma mansoni. Infected Biomphalaria glabrata snails have their cercarial shedding interrupted when exposed to PZQ. Using primary in vitro transformed sporocysts, labeled with the probe Hoechst 33258 (indicator of membrane integrity), and lectin of Glycine max (specific for carbohydrate of N-acetylgalactosamine membrane), we evaluated the presence of lysosomes at this evolutive phase of S. mansoni, as well as the influence of PZQ on these acidic organelles and on the tegument of the sporocyst. Although the sporocyst remained alive, it was observed that there was a marked contraction of its musculature, and there occurred a change in the parasite's structure. Also, the acidic vesicles found in the sporocysts showed a larger delimited area after contact of the parasites with PZQ. Damages to the tegument was also observed, as show a well-marked labeling either with Hoechst 33258 or with lectin of Glycine max after contact of sporocysts with the drug. These results could partially explain the interruption/reduction mechanism of cercarial shedding in snails exposed to PZQ

Schistosoma mansoni: a method for inducing resistance to praziquantel using infected Biomphalaria glabrata snails

To elucidate the mechanisms of antischistosoma resistance, drug-resistant Schistosoma mansoni laboratory isolates are essential. We developed a new method for inducing resistance to praziquantel (PZQ) using successive drug treatments of Biomphalaria glabrata snails infected with S. mansoni. Infected B. glabrata were treated three times with 100 mg/kg PZQ for five consecutive days with a one-week interval between them. After the treatment, the cercariae (LE-PZQ) produced from these snails and the LE strains (susceptible) were used to infect mice. Forty-five days after infection, mice were treated with 200, 400 or 800 mg/kg PZQ. Thirty days post-treatment, we observed that the mean number of worms recovered by perfusion was significantly higher in the group of mice infected with the LE-PZQ isolate treated with 200 and 400 mg/kg in comparison to the LE strain with the same treatment. Moreover, there was a significant difference between the ED50 (effective dose required to kill 50% of the worms) of the LE-PZQ isolate (362 mg/kg) and the LE strain (68 mg/kg). In the in vitro assays, the worms of the LE-PZQ isolate were also less susceptible to PZQ. Thus, the use of infected snails as an experimental model for development of resistance to S. mansoni is effective, fast, simple and cheap