The genome and transcriptome of the snail Biomphalaria sudanica s.l.: immune gene diversification and highly polymorphic genomic regions in an important African vector of Schistosoma mansoni.

BACKGROUND: Control and elimination of schistosomiasis is an arduous task, with current strategies proving inadequate to break transmission. Exploration of genetic approaches to interrupt Schistosoma mansoni transmission, the causative agent for human intestinal schistosomiasis in sub-Saharan Africa and South America, has led to genomic research of the snail vector hosts of the genus Biomphalaria. Few complete genomic resources exist, with African Biomphalaria species being particularly underrepresented despite this being where the majority of S. mansoni infections occur. Here we generate and annotate the first genome assembly of Biomphalaria sudanica sensu lato, a species responsible for S. mansoni transmission in lake and marsh habitats of the African Rift Valley. Supported by whole-genome diversity data among five inbred lines, we describe orthologs of immune-relevant gene regions in the South American vector B. glabrata and present a bioinformatic pipeline to identify candidate novel pathogen recognition receptors (PRRs). RESULTS: De novo genome and transcriptome assembly of inbred B. sudanica originating from the shoreline of Lake Victoria (Kisumu, Kenya) resulted in a haploid genome size of ~ 944.2 Mb (6,728 fragments, N50 = 1.067 Mb), comprising 23,598 genes (BUSCO = 93.6% complete). The B. sudanica genome contains orthologues to all described immune genes/regions tied to protection against S. mansoni in B. glabrata, including the polymorphic transmembrane clusters (PTC1 and PTC2), RADres, and other loci. The B. sudanica PTC2 candidate immune genomic region contained many PRR-like genes across a much wider genomic region than has been shown in B. glabrata, as well as a large inversion between species. High levels of intra-species nucleotide diversity were seen in PTC2, as well as in regions linked to PTC1 and RADres orthologues. Immune related and putative PRR gene families were significantly over-represented in the sub-set of B. sudanica genes determined as hyperdiverse, including high extracellular diversity in transmembrane genes, which could be under pathogen-mediated balancing selection. However, no overall expansion in immunity related genes was seen in African compared to South American lineages. CONCLUSIONS: The B. sudanica genome and analyses presented here will facilitate future research in vector immune defense mechanisms against pathogens. This genomic/transcriptomic resource provides necessary data for the future development of molecular snail vector control/surveillance tools, facilitating schistosome transmission interruption mechanisms in Africa.

Different metazoan parasites, different transcriptomic responses, with new insights on parasitic castration by digenetic trematodes in the schistosome vector snail Biomphalaria glabrata.

BACKGROUND: Gastropods of the genus Biomphalaria (Family Planorbidae) are exploited as vectors by Schistosoma mansoni, the most common causative agent of human intestinal schistosomiasis. Using improved genomic resources, overviews of how Biomphalaria responds to S. mansoni and other metazoan parasites can provide unique insights into the reproductive, immune, and other systems of invertebrate hosts, and their responses to parasite challenges. RESULTS: Using Illumina-based RNA-Seq, we compared the responses of iM line B. glabrata at 2, 8, and 40 days post-infection (dpi) to single infections with S. mansoni, Echinostoma paraensei (both digenetic trematodes) or Daubaylia potomaca (a nematode parasite of planorbid snails). Responses were compared to unexposed time-matched control snails. We observed: (1) each parasite provoked a distinctive response with a predominance of down-regulated snail genes at all time points following exposure to either trematode, and of up-regulated genes at 8 and especially 40dpi following nematode exposure; (2) At 2 and 8dpi with either trematode, several snail genes associated with gametogenesis (particularly spermatogenesis) were down-regulated. Regarding the phenomenon of trematode-mediated parasitic castration in molluscs, we define for the first time a complement of host genes that are targeted, as early as 2dpi when trematode larvae are still small; (3) Differential gene expression of snails with trematode infection at 40dpi, when snails were shedding cercariae, was unexpectedly modest and revealed down-regulation of genes involved in the production of egg mass proteins and peptide processing; and (4) surprisingly, D. potomaca provoked up-regulation at 40dpi of many of the reproduction-related snail genes noted to be down-regulated at 2 and 8dpi following trematode infection. Happening at a time when B. glabrata began to succumb to D. potomaca, we hypothesize this response represents an unexpected form of fecundity compensation. We also document expression patterns for other Biomphalaria gene families, including fibrinogen domain-containing proteins (FReDs), C-type lectins, G-protein coupled receptors, biomphalysins, and protease and protease inhibitors. CONCLUSIONS: Our study is relevant in identifying several genes involved in reproduction that are targeted by parasites in the vector snail B. glabrata and that might be amenable to manipulation to minimize their ability to serve as vectors of schistosomes.

Potential of Ocotea indecora (Schott) Mez essential oil nanoemulsion in schistosomiasis control: Molluscicidal effects.

Schistosomiasis is a neglected disease transmitted through contaminated water in populations with low basic sanitation. The World Health Organization recommends controlling the intermediate host snails of the Biomphalaria genus with the molluscicide niclosamide. This work aims to evaluate the biocidal potential of the nanoemulsion prepared with the essential oil of Ocotea indecora leaves for the control of the mollusk Biomphalaria glabrata, intermediate host of the Schistosoma mansoni, the etiologic agent of schistosomiasis.

Metabolic disruptions in Biomphalaria glabrata induced by Heterorhabditis bacteriophora HP88: Implications for entomopathogenic nematodes in biological control.

Research on the use of entomopathogenic nematodes (EPNs) as a potential tool for the biological control of invertebrates has been growing in recent years, including studies involving snails with One Health importance. In this study, the effect of exposure time (24 or 48 h) of Heterorhabditis bacteriophora HP88 on the activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), as well as the concentration of total proteins, uric acid, and urea in the hemolymph of Biomphalaria glabrata, were investigated. The concentrations of these metabolic markers were measured weekly until the end of the third week after exposure. Along with a significant reduction in total protein levels, a significant increase (p < 0.01) in uric acid and urea contents in the hemolymph of B. glabrata exposed to H. bacteriophora was observed. The accumulation of urea in these mollusks could lead to deleterious effects due to its high toxicity, inducing significant cell damage. Variations in transaminase activities were also observed, with snails exposed to EPNs showing significantly higher values (p < 0.01) than individuals in the control group, both for ALT and AST. These results indicate that experimental exposure to infective juveniles of H. bacteriophora causes significant alterations in the metabolic pattern of B. glabrata, compromising the maintenance of its homeostasis. Finally, exposure for 48 h caused more damage to the planorbid in question compared to snails exposed for 24 h, suggesting that the exposure time may influence the intensity of the host's response.

Biological, biochemical and genotoxicological alterations of Benzylamine on Biomphalaria alexandrina snails and its Schistosoma mansoni larvicidal potential.

Biomphalaria spp. snails are freshwater gastropods that responsible for Schistosoma mansoni transmission. Schistosomiasis is a chronic illness that occurred in underdeveloped regions with poor sanitation. The aim of the present study is to evaluate the molluscicidal activity of benzylamine against B. alexandrina snails and it larvicidal effects on the free larval stages of S. mansoni. Results showed that benzylamine has molluscicidal activity against adult B. alexandrina snails after 24 h of exposure with median lethal concentration (LC50) 85.7 mg/L. The present results indicated the exposure of B. alexandrina snails to LC10 or LC25 of benzylamine resulted in significant decreases in the survival, fecundity (eggs/snail/week) and reproductive rates, acetylcholinesterase, albumin, protein, uric acid and creatinine concentrations, levels of Testosterone (T) and 17ß Estradiol (E), while alkaline phosphatase levels were significantly increased in comparison with control ones. The present results showed that the sub lethal concentration LC50 (85.7 mg/L) of benzylamine has miracidial and cercaricidal activities, where the Lethal Time (LT50) for miracidiae was 17.08 min while for cercariae was 30.6 min. Also, results showed that were decreased significantly after exposure to sub lethal concentrations compared with control. The present results showed that the expression level of NADH dehydrogenase subunit 1 (ND1) genes and cytochrome oxidase subunit I (COI) in B. alexandrina snails exposed to LC10 or LC25 concentrations benzylamine were significantly decreased compared to the control groups. Therefore, benzylamine could be used as effective molluscicide to control schistosomiasis.

Activities of pumpkin seed oil against Biomphalaria alexandrina snails and the infective stages of Schistosoma mansoni with special emphasis on genotoxic and histopathological alterations.

Schistosomiasis is a serious health issue in tropical regions, and natural compounds have gained popularity in medical science. This study investigated the potential effects of pumpkin seed oil (PSO) on Biomphalaria [B.] alexandrina snails (Ehrenberg, 1831), Schistosoma [S.] mansoni (Sambon, 1907) miracidium, and cercariae. The chemical composition of PSO was determined using gas chromatography/mass spectrometry. A bioassay was performed to evaluate the effects of PSO on snails, miracidia, and cercariae. The results showed no significant mortality of B. alexandrina snails after exposure to PSO, but it caused morphological changes in their hemocytes at 1.0 mg/ml for 24 hours. PSO exhibited larvicidal activity against miracidia after 2 hours of exposure at a LC50 of 618.4 ppm. A significant increase in the mortality rate of miracidia was observed in a dose- and time-dependent manner, reaching a 100% death rate after 10 minutes at LC90 and 15 minutes at LC50 concentration. PSO also showed effective cercaricidal activity after 2 hours of exposure at a LC50 of 290.5 ppm. Histological examination revealed multiple pathological changes in the digestive and hermaphrodite glands. The PSO had genotoxic effects on snails, which exhibited a significant increase [p≤0.05] in comet parameters compared to the control. The findings suggest that PSO has potential as a molluscicide, miracidicide, and cercaricide, making it a possible alternative to traditional molluscicides in controlling schistosomiasis.

First report of Biomphalaria tenagophila (d'Orbigny, 1835) (Gastropoda/Planorbidae) in Pará State, Amazon region of Brazil.

INTRODUCTION: Mollusks belonging to Biomphalaria genus are intermediate hosts of Schistosoma mansoni. In the Pará State, Northern Region of Brazil, there are reports of B. glabrata, B. straminea, B. schrammi, B. occidentalis, and B. kuhniana occurrence. Here, we report for the first time the presence of B. tenagophila in Belém, capital of Pará state. METHODS: A total of 79 mollusks were collected and examined to search for possible S. mansoni infection. The specific identification was made by morphological and molecular assays. RESULTS: No specimens parasitized by trematode larvae were detected. For the first time the presence of B. tenagophila in Belém, capital of Pará state, was reported. CONCLUSION: The result increases the knowledge about Biomphalaria mollusks occurrence in the Amazon Region and specifically alerts on the possible role of B. tenagophila in schistosomiasis transmission in Belém.

Experimental infection with Schistosoma mansoni from Belém, Pará, Brazil: Strains newly isolated vs. laboratory maintained.

BACKGROUND: Schistosomiasis is a neglected tropical disease that occurs in locations with inadequate sanitation conditions. The geographic distribution of Schistosoma mansoni trematode depends directly on the presence of its intermediate host, Biomphalaria mollusks. Studies involving recently isolated and laboratory strains are not common due to the difficulty in cycle maintenance. This study evaluated the susceptibility and infectivity responses in intermediate and definitive hosts with strains of S. mansoni, one isolated and kept in laboratory environment for 34 years (BE) and the other recently collected (BE-I) METHODS: For experimental infection, a total of 400 B. glabrata mollusks were divided in four infection groups. Thirty mice were divided in two groups for infection with the two strains. RESULTS: It was possible to notice differences about S. mansoni infection in both strains. The laboratory strain was more harmful to freshly collected mollusks. Differences in the patterns of infection in mice could be observed. CONCLUSION: Particularities occurred in each group of infection by S. mansoni strains, despite having the same geographic origin. Effects from the parasite-host interaction are visible in terms of infection in definitive and intermediate hosts.

Inhibition of carbonic anhydrase using aspirin is a novel method to block schistosomiasis infection of the parasitic trematode, Schistosoma mansoni, in the intermediate snail host, Biomphalaria glabrata.

Schistosomiasis is a major public health concern worldwide. Although praziquantel is currently available as the only treatment option for schistosomiasis, the absence of reliable diagnostic and prognostic tools highlights the need for the identification and characterization of new drug targets. Recently, we identified the B. glabrata homolog (accession number XP_013075832.1) of human CAXIV, showing 37% amino acid sequence identity, from a BLAST search in NCBI (National Center for Biotechnology Information). Carbonic Anhydrases (CAs) are metalloenzymes that catalyze the reversible hydration/dehydration of CO2/HCO3. These enzymes are associated with many physiological processes, and their role in tumorigenesis has been widely implicated. CAs create an acidic extracellular environment that facilitates the survival, metastasis, and growth of cancer cells. In this study, we investigated the role of CA inhibition in B. glabrata snails exposed to S. mansoni miracidia. We analyzed the expression of the B. glabrata CA encoding transcript in juvenile susceptible and resistant snails, with and without exposure to S. mansoni. Our results showed that the expression of the CA mRNA encoding transcript was upregulated during early and prolonged infection in susceptible snails (BBO2), but not in the resistant BS-90 stock. Notably, sodium salicylate, a form of aspirin, inhibited the expression of CA, post-exposure, to the parasite. Increasing research between parasites and cancer has shown that schistosomes and cancer cells share similarities in their capacity to proliferate, survive, and evade host immune mechanisms. Here, we show that this model system is a potential new avenue for understanding the role of CA in the metastasis and proliferation of cancer cells. Further studies are needed to explore the potential of CA as a biomarker for infection in other schistosomiasis-causing parasites, including S. japonicum and S. haematobium.

Toxicological, hepato-renal, endocrine disruption, oxidative stress and immunohistopathological responses of chitosan capped gold nanocomposite on Biomphalaria alexandrina snails.

The present investigation aimed to synthesize chitosan­gold nanocomposites (Ch-AuNPs) with gamma radiation, then to evaluate its toxic effect on the freshwater snails Biomphalaia alexandrina. Results showed that Ch-AuNPs is spherical shaped with average size 12 nm. It had a toxic effect against B. alexandrina snails with LC50 20.43 mg/l. Exposure of B. alexandrina snails to LC10 7.51 or LC25 13.63 mg/l of Ch-AuNPs, reduced the survival, reproductive and fecundity rates; total protein and albumin; both testosterone (T) and 17ß Estradiol (E) levels; SOD and CAT activities of exposed snails while increased the activities of transaminases (AST & ALT), uric acid, creatinine, TAC and MDA levels compared to the control group. Results were supported by histopathological and immunohistopathological alterations of the digestive and hermaphrodite glands. In conclusion B. alexandrina could be used as a model to screen the negative impact of nanomaterials. Also, Ch-AuNPs could be used as a molluscicidal agent.

Toxicological effects of Saponin on the free larval stages of Schistosoma mansoni, infection rate, some biochemical and molecular parameters of Biomphalaria alexandrina snails.

Saponins have been used as biopesticides. The objective of the present study is to investigate the toxic effects of Saponin against Biomphalaria alexandrina snails. Results showed that Saponin exhibited a molluscicidal activity against adult B. alexandrina snails at LC50 (70.05 mg/l) and had a larvicidal effect on the free larval stages of Schistosoma mansoni. To evaluate the lethal effects, snails were exposed to either LC10 (51.8 mg/l) or LC25 (60.4 mg/l) concentrations of Saponin. The survival, the infection rates, protein, albumin, and total fat levels were decreased, while glucose levels were increased in exposed snails compared to control snails. Also, these concentrations significantly raised Malondialdehyde (MDA) and Glutathione S Transferase (GST) levels, whereas reduced Superoxide dismutase (SOD) activity and the total antioxidant capacity (TAC) in exposed snails. Furthermore, these concentrations resulted in endocrine disruptions where it caused a significant increase in testosterone (T) level; while a significant decrease in Estradiol (E2) levels were noticed. As for Estrogen (E) level, it was increased after exposure to LC10 Saponin concentration while after exposure to LC25 concentration, it was decreased. Also, LC10 and LC25 concentrations of Saponin caused a genotoxic effect and down-regulation of metabolic cycles in the snails. In conclusion, Saponins caused deleterious effects on the intermediate host of schistosomiasis mansoni. Therefore, B. alexandrina snails could be used as models to screen the toxic effects of Saponins in the aquatic environment and if it was used as a molluscicide, it should be used cautiously and under controlled circumstances.

Expression and Characterisation of the First Snail-Derived UDP-Gal: Glycoprotein-N-acetylgalactosamine ß-1,3-Galactosyltransferase (T-Synthase) from Biomphalaria glabrata.

UDP-Gal: glycoprotein-N-acetylgalactosamine ß-1,3-galactosyltransferase (T-synthase, EC 2.4.1.122) catalyses the transfer of the monosaccharide galactose from UDP-Gal to GalNAc-Ser/Thr, synthesizing the core 1 mucin type O-glycan. Such glycans play important biological roles in a number of recognition processes. The crucial role of these glycans is acknowledged for mammals, but a lot remains unknown regarding invertebrate and especially mollusc O-glycosylation. Although core O-glycans have been found in snails, no core 1 ß-1,3-galactosyltransferase has been described so far. Here, the sequence of the enzyme was identified by a BlastP search of the NCBI Biomphalaria glabrata database using the human T-synthase sequence (NP_064541.1) as a template. The obtained gene codes for a 388 amino acids long transmembrane protein with two putative N-glycosylation sites. The coding sequence was synthesised and expressed in Sf9 cells. The expression product of the putative enzyme displayed core 1 ß-1,3-galactosyltransferase activity using pNP-α-GalNAc as the substrate. The enzyme showed some sequence homology (49.40% with Homo sapiens, 53.69% with Drosophila melanogaster and 49.14% with Caenorhabditis elegans) and similar biochemical parameters with previously characterized T-synthases from other phyla. In this study we present the identification, expression and characterisation of the UDP-Gal: glycoprotein-N-acetylgalactosamine ß-1,3-galactosyltransferase from the fresh-water snail Biomphalaria glabrata, which is the first cloned T-synthase from mollusc origin.

Lethality and Acetylcholinesterase Inhibition in a Native Invertebrate Species Exposed to Water Samples of an Impacted Stream (Reconquista River Basin, Argentina).

The study of multiple biomarkers in bioindicator species is a useful tool to evaluate water quality in addition to physicochemical analysis. The aim of this work was to study the toxicity of water samples from two sites with different anthropogenic impacts (R: near a residential area and FP: close to horticultural farms and industrial waste treatment plants) from Las Catonas sub-basin (Reconquista River basin) in the native gastropod Biomphalaria straminea. Some physicochemical parameters and chlorpyrifos concentration were measured in water samples. Snails were exposed in laboratory conditions 48 h to the water samples and neurotoxicity, behavior, lethality and acetylcholinesterase, carboxylesterase, glutathione S-transferase, glutathione reductase and catalase activities were measured. In water from FP, chlorpyrifos was detected and conductivity and pH were higher than in R. Lethality (60%) and a decrease (30%) in acetylcholinesterase were observed in snails exposed to FP indicating that water contamination causes high toxicity in B. straminea.

Effects of Commercial Sunscreens on Survival, Reproduction and Embryonic Development of the Aquatic Snail Biomphalaria glabrata (SAY, 1818).

Over the past few years, there has been a significant increase in the use of sunscreens. Consequently, the occurrence in aquatic environments of ultraviolet filters has also increased. The present study aims to evaluate the toxicity of two commercial sunscreens to the aquatic snail Biomphalaria glabrata. Acute assays were performed with adult snails exposed to solutions of the two products in synthetic soft water. Reproduction and development assays were carried out, involving individual adult and egg masses exposure to assess fertility and embryonic development. Sunscreen A showed a LC50-96 h of 6.8 g/L and reduction in number of eggs and egg masses per individual in the concentration of 0.3 g/L. Sunscreen B presented higher malformation rates in 0.4 g/L with 63% of malformed embryos. Results indicate that the formulation used in sunscreens is an important factor in aquatic toxicity and needs to be evaluated before the final product is commercialized.

Single-cell RNA-seq profiling of individual Biomphalaria glabrata immune cells with a focus on immunologically relevant transcripts.

The immune cells of the snail Biomphalaria glabrata are classified into hyalinocyte and granulocyte subtypes. Both subtypes are essential for the proper functioning of the snail immune response, which we understand best within the context of how it responds to challenge with the human parasite Schistosoma mansoni. Granulocytes are adherent phagocytic cells that possess conspicuous granules within the cell cytoplasm. Hyalinocytes, on the other hand, are predominantly non-adherent and are known to produce a handful of anti-S. mansoni immune effectors. While our understanding of these cells has progressed, an in-depth comparison of the functional capabilities of each type of immune cell has yet to be undertaken. Here, we present the results of a single-cell RNA-seq study in which single granulocytes and hyalinocytes from S. mansoni-susceptible M-line B. glabrata and S. mansoni-resistant BS-90 B. glabrata are compared without immune stimulation. This transcriptomic analysis supports a role for the hyalinocytes as producers of immune effectors such as biomphalysin and thioester-containing proteins. It suggests that granulocytes are primarily responsible for producing fibrinogen-related proteins and are armed with various pattern-recognition receptors such as toll-like receptors with a confirmed role in the anti-S. mansoni immune response. This analysis also confirms that the granulocytes and hyalinocytes of BS-90 snails are generally more immunologically prepared than their M-line counterparts. As the first single-cell analysis of the transcriptional profiles of B. glabrata immune cells, this study provides crucial context for understanding the B. glabrata immune response. It sets the stage for future investigations into how each immune cell subtype differs in its response to various immunological threats.

Recombinant Snail Sialic Acid Aldolase is Promiscuous towards Aliphatic Aldehydes.

Aldolases are enzymes that reversibly catalyze the cleavage of carbon-carbon bonds. Here we describe a recombinant sialic acid aldolase originating from the freshwater snail Biomphalaria glabrata (sNPL), and compare its substrate spectrum with a sialic acid aldolase originating from chicken (chNPL). In contrast to vertebrate animals which can synthesize, degrade, and incorporate sialic acids on glycoconjugate ubiquitously, snails (as all mollusks) cannot synthesize sialic acids endogenously, and therefore the biological function and substrate scope of sNPL ought to differ significantly from vertebrate sialic aldolases such as chNPL. sNPL was active towards a series of sialic acid derivatives but was in contrast to chNPL unable to catalyze the cleavage of N-acetylneuraminic acid into N-acetylmannosamine and pyruvate. Interestingly, chNPL and sNPL showed contrasting C4(R)/(S) diastereoselectivity towards the substrates d-mannose and d-galactose in the presence of pyruvate. In addition, sNPL was able to synthesize a series of 4-hydroxy-2-oxoates using the corresponding aliphatic aldehyde substrates in the presence of pyruvate, which could be not achieved by chNPL.

A new accumulation assay of Schistosoma mansoni miracidia using square capillary glass tubes.

Current control measures for schistosomiasis have only been partially successful in endemic areas due to socioeconomic constraints. One possibility for controlling the disease is to aim at the miracidial stage of the trematode to avoid infecting intermediate snail hosts by introducing more attractive substances for miracidia in the environment. Here, we introduce an accumulation assay of Schistosoma mansoni miracidia using a square glass tube for analysis of the positive responses of miracidia toward several substances, including snail-conditioned water of Biomphalaria glabrata, Bulinus globosus and insusceptible snails collected in the Nagasaki area in Japan. The substances are not proteins because miracidia accumulated in boiled snail-conditioned water and the secretion or emission level of substances depended on the feeding conditions of Biomphalaria glabrata. The present study also showed that substances emitted from Biomphalaria glabrata with a molecular weight around 10 kDa accumulated Schistosoma mansoni miracidia. Further, we showed that Schistosoma mansoni miracidia did not accumulate in response to mono- or disaccharides tested in the study.

Snail juvenile growth rate as a rapid predictor of the transmission potential of parasitizing human schistosomes.

Host and parasite traits that are sensitive to environmental perturbations merit special attention in the mitigation of diseases. While life table experiments allow a practical evaluation of variability of these traits with environmental change, they are cost and resource intensive. Here, we use a model snail host-trematode parasite system to test the efficacy of an expeditious alternative. Rapidly changing host traits (such as juvenile growth rate) can be used as effective predictors of parasite transmission potential across a range of environmental factors. This approach can be applied to anticipate epidemiological changes under diverse environmental scenarios.

Algal-Derived Halogenated Sesquiterpenes from Laurencia dendroidea as Lead Compounds in Schistosomiasis Environmental Control.

Schistosomiasis has been controlled for more than 40 years with a single drug, praziquantel, and only one molluscicide, niclosamide, raising concern of the possibility of the emergence of resistant strains. However, the molecular targets for both agents are thus far unknown. Consequently, the search for lead compounds from natural sources has been encouraged due to their diverse structure and function. Our search for natural compounds with potential use in schistosomiasis control led to the identification of an algal species, Laurencia dendroidea, whose extracts demonstrated significant activity toward both Schistosoma mansoni parasites and their intermediate host snails Biomphalaria glabrata. In the present study, three seaweed-derived halogenated sesquiterpenes, (-)-elatol, rogiolol, and obtusol are proposed as potential lead compounds for the development of anthelminthic drugs for the treatment of and pesticides for the environmental control of schistosomiasis. The three compounds were screened for their antischistosomal and molluscicidal activities. The screening revealed that rogiolol exhibits significant activity toward the survival of adult worms, and that all three compounds showed activity against S. mansoni cercariae and B. glabrata embryos. Biomonitored fractioning of L. dendroidea extracts indicated elatol as the most active compound toward cercariae larvae and snail embryos.

Toxicological impact of organophosphorus Chlorpyrifos 48%EC pesticide on hemocytes, biochemical disruption, and molecular changes in Biomphalaria alexandrina snails.

Organophosphorus pesticides like Chlorpyrifos 48%EC were widely used to control agricultural pests. The present study aimed to evaluate the toxic effects of Chlorpyrifos 48%EC on B. alexandrina snails, the intermediate host of Schistosoma mansoni. After exposure of snails to serial concentrations to determine the LC50, thirty snails for each sublethal concentration (LC10 2.1 and LC25 5.6 mg/l) in each group were exposed for 24 h followed by another 24 h for recovery. After recovery random samples were collected from hemolymph and tissue to measure the impacts on Phagocytic index, histological, biochemical, and molecular parameters. The current results showed a toxic effect of Chlorpyrifos 48%EC on adult B. alexandrina snails after 24 h of exposure at LC50 9.6 mg/l. After exposure to the sub-lethal concentrations of this pesticide, it decreased the total number of hemocytes and the percentage of small cells, while increased the percentage of hyalinocytes. The granulocyte percentage was increased after exposure to LC10, while after LC25, it was decreased compared to the control group. Also, the light microscopical examination showed that some granulocytes have plenty of granules, vacuoles and filopodia. Some hyalinocytes were contained shrinked nuclei, incomplete cell division and forming pseudopodia. Besides, the phagocytic index of hemocytes was significantly increased than control in all treated groups. Also, these sub-lethal concentrations increased MDA and SOD activities, while, tissue NO, GST and TAC contents were significantly decreased after exposure. Levels of Testosterone (T) and Estradiol (E) were increased significantly after exposure compared with control group. The present results showed that the concentration of DNA and RNA was highly decreased after exposure to LC10, 25 than the control group. Therefore, B. alexandrina snails could be used as a bio monitor of the chemical pollution. Besides, this pesticide could reduce the transmission of schistosomiasis as it altered the biological system of these snails.