Biomphalaria pfeifferi Snails and Intestinal Schistosomiasis, Lake Malawi, Africa, 2017-2018.
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ABSTRACT:
SUBMITTER: Alharbi MH
PROVIDER: S-EPMC6390747 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:BackgroundThe freshwater snail Biomphalaria acts as the intermediate host of Schistosoma mansoni, a globally important human parasite. Understanding the population structure of intermediate host species can elucidate transmission dynamics and assist in developing appropriate control methods.MethodsWe examined levels of population genetic structure and diversity in 29 populations of Biomphalaria choanomphala collected around the shoreline of Lake Victoria in Uganda, Kenya and Tanzania, where S. mansoni is hyper-endemic. Molecular markers were utilized to estimate the degree to which snail populations are genetically differentiated from one another.ResultsHigh levels of snail genetic diversity were found coupled with evidence of geographically-determined population structure but low levels of local inbreeding. The data are consistent with an effect of schistosome infection on population structure of intermediate host snails, but other factors, such as habitat and historical demographic changes, could also be important determinants of the degree of population genetic structure in Biomphalaria choanomphala.ConclusionsThe low stratification of populations and high genetic diversity indicates potentially less local compatibility with intermediate snail populations than previously theorized, and highlights the importance of coordinated parasite control strategies across the region.
| S-EPMC4254209 | biostudies-literature
Project description:Biomphalaria pfeifferi Genome sequencing
| PRJNA383396 | ENA
Project description:Schistosomiasis, which infects more than 230 million people, is vectored by freshwater snails. We identified viral sequences in the transcriptomes of Biomphalaria pfeifferi (BP) and Bulinus globosus (BuG), two of the world’s most important schistosomiasis vectors in Africa. Sequences from 26 snails generated using Illumina Hi-Seq or 454 sequencing were assembled using Trinity and CAP3 and putative virus sequences were identified using a bioinformatics pipeline. Phylogenetic analyses were performed using viral RNA-dependent RNA polymerase and coat protein sequences to establish relatedness between virus sequences identified and those of known viruses. Viral sequences were identified from the entire snail holobiont, including symbionts, ingested material and organisms passively associated with the snails. Sequences derived from more than 17 different viruses were found including five near full-length genomes, most of which were small RNA viruses with positive sense RNA genomes (i.e., picorna-like viruses) and some of which are likely derived from adherent or ingested diatoms. Based on phylogenetic analysis, five of these viruses (including BPV2 and BuGV2) along with four Biomphalaria glabrata viruses reported previously, cluster with known invertebrate viruses and are putative viruses of snails. The presence of RNA sequences derived from four of these novel viruses in samples was confirmed. Identification of the genome sequences of candidate snail viruses provides a first step toward characterization of additional gastropod viruses, including from species of biomedical significance.
| S-EPMC8601052 | biostudies-literature
Project description:Lake Victoria is a known hot-spot for Schistosoma mansoni, which utilises freshwater snails of the genus Biomphalaria as intermediate hosts. Different species of Biomphalaria are associated with varying parasite compatibility, affecting local transmission. It is thought that two species, B. choanomphala and B. sudanica, inhabit Lake Victoria; despite their biomedical importance, the taxonomy of these species has not been thoroughly examined. This study combined analysis of morphological and molecular variables; the results demonstrated that molecular groupings were not consistent with morphological divisions. Habitat significantly predicted morphotype, suggesting that the different Lake Victorian forms of Biomphalaria are ecophentoypes of one species. The nomenclature should be revised accordingly; the names B. choanomphala choanomphala and B. c. sudanica are proposed. From a public health perspective, these findings can be utilised by policy-makers for better understanding of exposure risk, resulting in more effective and efficient control initiatives.
| S-EPMC3200340 | biostudies-literature
Project description:Background: Schistosomiasis is one of the world's most common NTDs. Successful control operations often target snail vectors with the molluscicide niclosamide. Little is known about how niclosamide affects snails, including for Biomphalaria pfeifferi, the most important vector for Schistosoma mansoni in Africa. We used Illumina technology to explore how field-derived B. pfeifferi, either uninfected or harboring cercariae-producing S. mansoni sporocysts, respond to a sublethal treatment of niclosamide. This study afforded the opportunity to determine if snails respond differently to biotic or abiotic stressors, and if they reserve unique responses for when presented with both stressors in combination. We also examined how sporocysts respond when their snail host is treated with niclosamide.Principal findings: Cercariae-producing sporocysts within snails treated with niclosamide express ~68% of the genes in the S. mansoni genome, as compared to 66% expressed by intramolluscan stages of S. mansoni in snails not treated with niclosamide. Niclosamide does not disable sporocysts nor does it seem to provoke from them distinctive responses associated with detoxifying a xenobiotic. For uninfected B. pfeifferi, niclosamide treatment alone increases expression of several features not up-regulated in infected snails including particular cytochrome p450s and heat shock proteins, glutathione-S-transferases, antimicrobial factors like LBP/BPI and protease inhibitors, and also provokes strong down regulation of proteases. Exposure of infected snails to niclosamide resulted in numerous up-regulated responses associated with apoptosis along with down-regulated ribosomal and defense functions, indicative of a distinctive, compromised state not achieved with either stimulus alone.Conclusions/significance: This study helps define the transcriptomic responses of an important and under-studied schistosome vector to S. mansoni sporocysts, to niclosamide, and to both in combination. It suggests the response of S. mansoni sporocysts to niclosamide is minimal and not reflective of a distinct repertoire of genes to handle xenobiotics while in the snail host. It also offers new insights for how niclosamide affects snails.
| S-EPMC6936870 | biostudies-literature
Project description: Not available
| S-EPMC2630743 | biostudies-literature
Project description:Background: The full scope of the genes expressed by schistosomes during intramolluscan development has yet to be characterized. Understanding the gene products deployed by larval schistosomes in their snail hosts will provide insights into their establishment, maintenance, asexual reproduction, ability to castrate their hosts, and their prolific production of human-infective cercariae. Using the Illumina platform, the intramolluscan transcriptome of Schistosoma mansoni was investigated in field-derived specimens of the prominent vector species Biomphalaria pfeifferi at 1 and 3 days post infection (d) and from snails shedding cercariae. These S. mansoni samples were derived from the same snails used in our complementary B. pfeifferi transcriptomic study. We supplemented this view with microarray analyses of S. mansoni from B. glabrata at 2d, 4d, 8d, 16d, and 32d to highlight robust features of S. mansoni transcription, even when a different technique and vector species was used.Principal findings: Transcripts representing at least 7,740 (66%) of known S. mansoni genes were expressed during intramolluscan development, with the greatest number expressed in snails shedding cercariae. Many transcripts were constitutively expressed throughout development featuring membrane transporters, and metabolic enzymes involved in protein and nucleic acid synthesis and cell division. Several proteases and protease inhibitors were expressed at all stages, including some proteases usually associated with cercariae. Transcripts associated with G-protein coupled receptors, germ cell perpetuation, and stress responses and defense were well represented. We noted transcripts homologous to planarian anti-bacterial factors, several neural development or neuropeptide transcripts including neuropeptide Y, and receptors that may be associated with schistosome germinal cell maintenance that could also impact host reproduction. In at least one snail the presence of larvae of another digenean species (an amphistome) was associated with repressed S. mansoni transcriptional activity.Conclusions/significance: This in vivo study, emphasizing field-derived snails and schistosomes, but supplemented with observations from a lab model, provides a distinct view from previous studies of development of cultured intramolluscan stages from lab-maintained organisms. We found many highly represented transcripts with suspected or unknown functions, with connection to intramolluscan development yet to be elucidated.
| S-EPMC6797213 | biostudies-literature
Project description:Human schistosomiasis is a common parasitic disease endemic in many tropical and subtropical countries. One barrier to achieving long-term control of this disease has been re-infection of treated patients when they swim, bathe, or wade in surface fresh water infested with snails that harbor and release larval parasites. Because some snail species are obligate intermediate hosts of schistosome parasites, removing snails may reduce parasitic larvae in the water, reducing re-infection risk. Here, we evaluate the potential for snail control by predatory freshwater prawns, Macrobrachium rosenbergii and M. vollenhovenii, native to Asia and Africa, respectively. Both prawn species are high value, protein-rich human food commodities, suggesting their cultivation may be beneficial in resource-poor settings where few other disease control options exist. In a series of predation trials in laboratory aquaria, we found both species to be voracious predators of schistosome-susceptible snails, hatchlings, and eggs, even in the presence of alternative food, with sustained average consumption rates of 12% of their body weight per day. Prawns showed a weak preference for Bulinus truncatus over Biomphalaria glabrata snails. Consumption rates were highly predictable based on the ratio of prawn: snail body mass, suggesting satiation-limited predation. Even the smallest prawns tested (0.5-2g) caused snail recruitment failure, despite high snail fecundity. With the World Health Organization turning attention toward schistosomiasis elimination, native prawn cultivation may be a viable snail control strategy that offers a win-win for public health and economic development.
| S-EPMC4280914 | biostudies-literature
Project description:BACKGROUND:To complement ongoing schistosomiasis control within national control programmes (NCPs) that administer praziquantel to school-age children, assessing the risk and extent of schistosomiasis in pre-school-age children (PSAC) is important. METHODS:In June 2012, schistosomiasis in Chikhwawa district, Malawi was assessed across 12 villages examining pre-school-age children (PSAC) and their mothers by serological and parasitological diagnosis, as supplemented with urine-antigen and questionnaire-interview methods. Urinary tract morbidity was inferred by haematuria and albuminuria assays. RESULTS:In total, 49.5% (CI?? 42.6-56.4) of 208 PSAC and 94.5% (CI?? 90.9-98.1) of 165 mothers were seropositive for schistosomiasis, in 2 villages seroprevalence exceeded 75% in PSAC. Egg-patent urogenital and intestinal schistosomiasis was observed; 17.7% (CI?? 12.4-23.2) of PSAC and 45.1% (CI?? 37.4-52.8) of mothers having active schistosomiasis by parasitological and urine-antigen testing combined. PSAC often had extensive daily water contact and many (~25%) had haematuria and albuminuria. As eggs with an atypical morphology of Schistosoma haematobium were observed, a general selection of schistosome eggs was characterized by DNA barcoding, finding Group I S. haematobium and Group IV and V S. mansoni. Malacological surveys encountered several populations of Bulinus globosus but failed to find Biomphalaria. CONCLUSIONS:Both PSAC and their mothers appear to be at significant risk of schistosomiasis and should be considered for treatment within the NCP of Malawi.
| S-EPMC4230191 | biostudies-literature