Showing papers on "Bulinus truncatus published in 2019"

Freshwater snails of biomedical importance in the Niger River Valley: evidence of temporal and spatial patterns in abundance, distribution and infection with Schistosoma spp.

Abstract: Sound knowledge of the abundance and distribution of intermediate host snails is key to understanding schistosomiasis transmission and to inform effective interventions in endemic areas. A longitudinal field survey of freshwater snails of biomedical importance was undertaken in the Niger River Valley (NRV) between July 2011 and January 2016, targeting Bulinus spp. and Biomphalaria pfeifferi (intermediate hosts of Schistosoma spp.), and Radix natalensis (intermediate host of Fasciola spp.). Monthly snail collections were carried out in 92 sites, near 20 localities endemic for S. haematobium. All bulinids and Bi. pfeifferi were inspected for infection with Schistosoma spp., and R. natalensis for infection with Fasciola spp. Bulinus truncatus was the most abundant species found, followed by Bulinus forskalii, R. natalensis and Bi. pfeifferi. High abundance was associated with irrigation canals for all species with highest numbers of Bulinus spp. and R. natalensis. Seasonality in abundance was statistically significant in all species, with greater numbers associated with dry season months in the first half of the year. Both B. truncatus and R. natalensis showed a negative association with some wet season months, particularly August. Prevalences of Schistosoma spp. within snails across the entire study were as follows: Bi. pfeifferi: 3.45% (79/2290); B. truncatus: 0.8% (342/42,500); and B. forskalii: 0.2% (24/11,989). No R. natalensis (n = 2530) were infected. Seasonality of infection was evident for B. truncatus, with highest proportions shedding in the middle of the dry season and lowest in the rainy season, and month being a significant predictor of infection. Bulinus spp. and Bi. pfeifferi showed a significant correlation of snail abundance with the number of snails shedding. In B. truncatus, both prevalence of Schistosoma spp. infection, and abundance of shedding snails were significantly higher in pond habitats than in irrigation canals. Evidence of seasonality in both overall snail abundance and infection with Schistosoma spp. in B. truncatus, the main intermediate host in the region, has significant implications for monitoring and interrupting transmission of Schistosoma spp. in the NRV. Monthly longitudinal surveys, representing intensive sampling effort have provided the resolution needed to ascertain both temporal and spatial trends in this study. These data can inform planning of interventions and treatment within the region.

Molecular characterization and distribution of Schistosoma cercariae collected from naturally infected bulinid snails in northern and central Côte d’Ivoire

Abstract: Accurate identification of schistosome species infecting intermediate host snails is important for understanding parasite transmission, schistosomiasis control and elimination. Cercariae emerging from infected snails cannot be precisely identified morphologically to the species level. We used molecular tools to clarify the distribution of the Schistosoma haematobium group species infecting bulinid snails in a large part of Cote d’Ivoire and confirmed the presence of interspecific hybrid schistosomes. Between June 2016 and March 2017, Bulinus snails were sampled in 164 human-water contact sites from 22 villages of the northern and central parts of Cote d’Ivoire. Multi-locus genetic analysis (mitochondrial cox1 and nuclear ITS) was performed on individual schistosome cercariae shed from snails, in the morning and in the afternoon, for species and hybrid identification. Overall, 1923 Bulinus truncatus, 255 Bulinus globosus and 1424 Bulinus forskalii were obtained. Among 2417 Bulinus screened, 25 specimens (18 B. truncatus and seven B. globosus) shed schistosomes, with up to 14% infection prevalence per site and time point. Globally, infection rates per time point ranged between 0.6 and 4%. Schistosoma bovis, S. haematobium and S. bovis × S. haematobium hybrids infected 0.5%, 0.2% and 0.4% of the snails screened, respectively. Schistosoma bovis and hybrids were more prevalent in B. truncatus, whereas S. haematobium and hybrid infections were more prevalent in B. globosus. Schistosoma bovis-infected Bulinus were predominantly found in northern sites, while S. haematobium and hybrid infected snails were mainly found in central parts of Cote d’Ivoire. The data highlight the necessity of using molecular tools to identify and understand which schistosome species are transmitted by specific intermediate host snails. The study deepens our understanding of the epidemiology and transmission dynamics of S. haematobium and S. bovis in Cote d’Ivoire and provides the first conclusive evidence for the transmission of S. haematobium × S. bovis hybrids in this West African country. Trial registration ISRCTN, ISRCTN10926858. Registered 21 December 2016; retrospectively registered (see: http://www.isrctn.com/ISRCTN10926858 )

Molluscicidal effectiveness of Luo-Wei, a novel plant-derived molluscicide, against Oncomelania hupensis, Biomphalaria alexandrina and Bulinus truncatus

Abstract: Control of snail intermediate hosts has been proved to be a fast and efficient approach for interrupting the transmission of schistosomiasis. Some plant extracts have shown obvious molluscicidal activity, and a new compound Luo-Wei, also named tea-seed distilled saponin (TDS), was developed based on the saponins extracted from Camellia oleifera seeds. We aimed to test the molluscicidal activity of 4% TDS against the intermediate host snails in China and Egypt, and evaluate its environmental safety to non-target organisms. In the laboratory, Oncomelania hupensis, Biomphalaria alexandrina and Bulinus truncatus were exposed to 4% TDS, and the median lethal concentration (LC50) was estimated at 24, 48 and 72 h. In the field, snail mortalities were assessed 1, 2, 3 and 7 d post-immersion with 2.5 g/m3 4% TDS and 1, 3, 7 and 15 d post-spraying with 5 g/m2 4% TDS. In addition, the acute toxicity of 4% TDS to Japanese quail (Coturnix japonica), zebrafish (Brachydanio rerio) and freshwater shrimp (Macrobrachium nipponense) was assessed by estimations of LC50 or median lethal dose (LD50). In the laboratory, the LC50 values of 4% TDS for O. hupensis were 0.701, 0.371 and 0.33 mg/L at 24, 48 and 72 h, respectively, and 4% TDS showed a 1.975 mg/L 24 h LC50 against B. alexandrina, and a 1.396 mg/L 24 h LC50 against B. truncatus. Across all study regions, the pooled mortalities of O. hupensis were 72, 86, 94 and 98% at 1, 2, 3 and 7 d, following field immersion of 4% TDS at a dose of 2.5 g/m3, and were 69, 77, 85 and 88% at 1, 3, 7 and 15 d, following field spraying at 5 g/m2, respectively. 4% TDS had moderate toxicity to Japanese quail (7 d LD50 > 60 mg/kg) and to shrimp (96 h LC50 = 6.28 mg/L; 95% CI: 3.53–11.2 mg/L), whereas its toxicity to zebrafish was high (96 h LC50 = 0.15 mg/L; 95% CI: 0.14–0.17 mg/L). 4% TDS is active against O. hupensis, B. alexandrina and B. truncatus under laboratory and field conditions, and it may be a candidate molluscicide of plant origin.

Persistent establishment of a tropical disease in Europe: the preadaptation of schistosomes to overwinter

Abstract: Global changes promote the spread of infectious diseases worldwide. In this context, tropical urogenital schistosomiasis is now permanently established in Corsica since its first emergence in 2013. The local persistence of the tropical pathogens (schistosomes) responsible for urogenital schistosomiasis at such latitudes might be explained by (i) the presence of its intermediate host, the snail Bulinus truncatus, (ii) the recurrent local reseeding of schistosomes by their vertebrate hosts (either human or animal) every summer, and/or (iii) the maintenance and survival of schistosomes within their snail hosts over winter. In this study we conducted an ecological experiment to assess the ability of temperate and tropical schistosome strains to survive in classical winter temperatures in Corsican rivers when infecting temperate (local) snail strains. We also quantified the ability of the schistosomes to complete their life-cycle post-overwintering when returned to classical summer water temperatures. Our results show that Mediterranean molluscs are locally adapted to winter conditions compared to tropical molluscs. Moreover, temperate and tropical schistosome strains equally survived the cold and produced viable offspring when returned to optimal temperatures. These results indicate that schistosomes can overwinter under temperate climates when infecting locally adapted snails and might partly explain the establishment and maintenance of schistosomes in Corsica from year to year. The observed broader thermal range of schistosomes compared to that of their snail hosts was unexpected and clearly indicates that the spread and establishment of schistosomiasis in temperate countries relies primarily on the presence of the locally adapted snail host lineages, currently known to be present in France, Italy, Portugal, Spain and Greece.

Molecular identification of Bulinus spp. intermediate host snails of Schistosoma spp. in crater lakes of western Uganda with implications for the transmission of the Schistosoma haematobium group parasites.

Abstract: Human schistosomiasis is the second most important tropical disease and occurs in two forms in Africa (intestinal and urogenital) caused by the digenetic trematodes Schistosoma mansoni and Schistosoma haematobium, respectively. A proposed recent shift of schistosomiasis above a previously established altitudinal threshold of 1400 m above sea level in western Ugandan crater lakes has triggered more research interest there. Based on extensive field sampling in western Uganda and beyond and employing an approach using sequences of the mitochondrial barcoding gene cytochrome c oxidase subunit 1 (cox1) this study aims were: (i) identification and establishment of the phylogenetic affinities of Bulinus species as potential hosts for Schistosoma spp.; (ii) determining diversity, frequency and distribution patterns of Bulinus spp.; and (iii) establishing genetic variability and phylogeographical patterns using Bayesian inference and parsimony network analyses. Out of the 58 crater lakes surveyed, three species of Bulinus snails were found in 34 crater lakes. Bulinus tropicus was dominating, Bulinus forskalii was found in two lakes and Bulinus truncatus in one. The latter two species are unconfirmed potential hosts for S. haematobium in this region. However, Bulinus tropicus is an important species for schistosomiasis transmission in ruminants. Bulinus tropicus comprised 31 haplotypes while both B. forskalii and B. truncatus exhibited only a single haplotype in the crater lakes. All species clustered with most of the haplotypes from surrounding lake systems forming source regions for the colonization of the crater lakes. This first detailed malacological study of the crater lakes systems in western Uganda revealed presence of Bulinus species that are either not known or not regionally known to be hosts for S. haematobium, the causing agent of human urogenital schistosomiasis. Though this disease risk is almost negligible, the observed dominance of B. tropicus in the crater lakes shows that there is a likelihood of a high risk of infections with Schistosoma bovis. Thus, extra attention should be accorded to safeguard wild and domestic ruminants in this region as the population benefits from these animals.

Risk map of transmission of urogenital schistosomiasis by Bulinus truncatus (Audouin, 1827) (Mollusca Gastropoda, Bulinidae) in Spain and Portugal.

Abstract: espanolSe da a conocer el mapa de la distribucion geografica de Bulinus truncatus en Espana y Portugal en el que se recopilan las localidades historicas y actuales, que coincide con el mapa del riesgo de contraer schistosomiasis urogenital provocada por este caracol de agua dulce. Se revisan las muestras de esta especie depositadas en el Museu de Ciencies Naturals de Barcelona y en el Museo de Ciencias Naturales de Madrid, asi como datos propios, incluidas algunas aportaciones ineditas. Este mapa permitira conocer el area optima de esta especie y determinar las zonas de mayor riesgo de contraer schistosomiasis urogenital en los dos paises. Se pone de manifiesto que el cambio global y el cambio climatico pueden favorecer la presencia tanto del vector (B. truncatus) como del parasito (Schistosoma haematobium) en Espana y Portugal. EnglishRisk map of transmission of urogenital schistosomiasis by Bulinus truncatus (Audouin, 1827) (Mollusca Gastropoda, Bulinidae) in Spain and Portugal. We present a geographical distribution map of Bulinus truncatus based on historical and current localities in Spain and Portugal, that corresponds to the risk map of urogenital schistosomiasis for this freshwater snail. We reviewed samples of the species deposited at the Museu de Ciencies Naturals of Barcelona and the Museo Nacional de Ciencias Naturales of Madrid, together with our own data, including some unpublished contributions. This map will help determine the optimal area for this species and identify areas of greatest risk for urogenital schistosomiasis in the two countries. We emphasize that global change and climate change may favour the presence of both the vector (B. truncatus) and the parasite (Schistosoma haematobium) in Spain and Portugal.

Effect of copper coated lupine extract nanoparticles on some aquatic and terrestrial pest snails.

Abstract: Effect of lupine extracts nanoparticles (NPs) coated with copper sulphate on the mortality and eggs productivity of aquatic snails, Biomphalaria alexandrina Ehrenberg and Bulinus truncatus Audouin, and terrestrial snail, Eobania vermiculata Muller, were investigated in comparison with copper sulphate nanoparticles and both treatments compare with untreated group in the present and previous investigation. This experiment was planned to elucidate the molluscicidal properties of lupine extract coated with CuSO4 NPs against adult B. alexandrina B. truncatus and E. vermiculata snails after 24 hours exposure, in dark conditions, followed by another 48 hrs. light for recovery. The results revealed that lupine extracts nanoparticles has more effect than copper sulphate nanoparticles on both aquatic or terrestrial snail mortality. It caused 100% mortality for B. alexandrina and B. truncates, at concentration of 20 ppm, after 24 hours of exposure in dark followed by 48 hours recovery in day light. Copper sulphate nanoparticles at the same concentration caused only 70% and 46. 67% mortality for B. alexandrina and B. truncates, respectively, under the same conditions. Mortality rate increased with the increase of concentrations either in lupine NPs or CuO4 NPs. On normal lupine extract the concentration that caused 100% mortality was equal to ten folds of lupine NPs. Egg productivity of the healthy thirty individuals, of B. alexandrina, B. truncatus and E. vermiculata, were investigated and compared with the survival snails in low concentrations of both Cu NPs and lupine NPs, to study the effect of nanoparticle materials on the snail fecundity. Both lupine extract nanoparticles and copper sulphate nanoparticles may have a sterilized effect, where B. alexandrina and B. truncatus snails exposed to sub lethal doses from them didn’t laid any egg masses after treatment. E. vermiculata, treated or untreated individuals, didn’t laid any eggs either, because it had a specific season of reproduction which not coinciding with the time of experiment

Biological activity of artemisinin-naphthoquine phosphate on Schistosoma haematobium stages and the vector Bulinus truncatus

Abstract: BACKGROUND Schistosoma haematobium infection is a major public health problem in most of Africa and the Middle East and praziquantel remains the only drug used for schistosomiasis control, therefore emergence of drug resistance is unavoidable. The antimalarial artemisinin-naphthoquine phosphate combination (co-ArNp) was recently documented to have promising effects on Schistosoma mansoni and its snail host. METHODS We conducted this in vitro study to assess the bioactivity of co-ArNp on S. haematobium and its snail vector Bulinus truncatus. RESULTS Treatment of S. haematobium worms with 1 μg/ml co-ArNp for 24 h reduced worm motility, while 20 μg/ml resulted in 25-100% mortality of adult flukes within 48-72 h. Incubation of S. haematobium miracidia and cercariae with the molluscicidal co-ArNp (50% lethal concentration 7.5 μg/ml) killed all the free larval stages within 40 and 15 min, respectively. Also, exposure of B. truncatus adult snails to 20 ppm of the combined regimen caused a mortality rate of 100% within 24 h. CONCLUSIONS Co-ArNp therapy has also shown encouraging activity against the other major human schistosome, S. haematobium, as well as its vector.