Green synthesis of silver nanoparticles using Croton urucurana and their toxicity in freshwater snail species Biomphalaria glabrata.

Green silver nanoparticles (G-Ag NPs) have contributed to the development of ecological technologies with low environmental impact and safer for human health, as well as demonstrating potential for the control of vectors and intermediate hosts. However, knowledge about its toxicity in the early stages of gastropod development remains scarce. Therefore, the current study aimed to investigate the toxicity of G-Ag NPs synthesized from Croton urucurana leaf extracts in snail species Biomphalaria glabrata, which is an intermediate host for Schistosoma mansoni parasite. G-Ag NPs were synthesized using two types of plant extracts (aqueous and hydroethanolic) and characterized using multiple techniques. Bioassays focused on investigating G-Ag NPs and plant extracts were carried out with embryos and newly hatched snails, for 144 h and 96 h, respectively; toxicity was analyzed based on mortality, hatching, development inhibition, and morphological changes. Results have shown that both G-Ag NPs were more toxic to embryos and newly hatched snails than the investigated plant extracts. G-Ag NPs deriving from aqueous extract have higher molluscicidal activity than those deriving from hydroethanolic extract. Both G-Ag NPs induced mortality, hatching delay, development inhibition, and morphological changes (i.e., hydropic embryos), indicating their molluscicidal activities. Moreover, embryos were more sensitive to G-Ag NPs than newly hatched snails. Thus, the toxicity of G-Ag NPs to freshwater snails depends on the type of extracts and the snail's developmental stages. These findings can contribute to the development of green nanobiotechnologies applicable to control snails of medical importance.

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.

Bio-molluscicidal potential and biochemical mechanisms of clove oil and its main component eugenol against the land snail, Theba pisana.

The land snail, Theba pisana is a serious pest that adversely affects various crops in sustainable agriculture. Essential oils and their constituents represent an environmentally sound alternative to synthetic pesticides. Our study aimed to investigate the lethal and sub-lethal toxicity of clove oil and its main component eugenol to understand the mechanisms underlying its toxic action against T. pisana. The GC-MS profile of the clove oil composition was characterized. In the laboratory experiment, LD50 of clove oil and eugenol via the contact testing were determined after 48 and 72 h. Moreover, sub-lethal effects of clove oil or eugenol on the survivors following the exposure of snails to the 25 and 50% of the LD50/48 and 72 h were evaluated through using snail tissues for biochemical measurments. The GC-MS analysis showed that eugenol (64.87%) was the major constituent present in the oil. The results also showed that LD50 values at 48 and 72 h were 2006.5 and 1493.5 µg/g b.w for oil and 239.6 and 195.3 µg/g b.w for eugenol, respectively. Compared to control, the sub-lethal effects of clove oil or eugenol at 48 and 72 h showed a significant increase in reduced glutathione (GSH) levels. Catalase (CAT) and glutathione-S-transferase (GST) activities significantly elevated in oil- or eugenol-treated snails, except at low dose after 48 h. After two exposure times, snails exposed to oil or eugenol at both sub-lethal effects had considerably higher γ-glutamyltransferase (γ-GT) and aspartate aminotransferase (AST) activities. Moreover, markedly augmentation in alkaline phosphatase (ALP) and alanine aminotransferase (ALT) activities at all exposure times, with the exception of snails treated with low dose of eugenol after 48 h was observed. Both clove oil and eugenol at the tested doses caused a significant inhibition in acetylcholinesterase (AChE) activity at two exposure times. Our findings highlight the potential of clove oil and eugenol, as an efficient natural molluscicide alternative to its synthetic counterparts for snail control.

Molluscicidal activity of plant alkaloids.

Some snail species pose a serious threat for human health, economy, and the environment due to their widespread distribution and the transmission of dangerous parasites causing, among others, schistosomiasis and fascioliasis. Scientists from around the world have been studying the effects of plant extracts on snails for many years in order to find an alternative to molluscicides of synthetic origin. The main purpose of this study was to collect the results obtained so far on the effect of plant alkaloids on snails in the context of their molluscicidal properties. This work presents the results of publications on the effect of plant alkaloids on snails, which were published in the years 1974-2021. The Solanaceae, Papaveraceae, and Asteraceae are the plant families most frequently cited for containing alkaloids with molluscicidal activity. The alkaloids identified as molluscicidal belonged to various groups, of which the most numerous were pseudoalkaloids and tyrosine-derived alkaloids. Most of the tested alkaloids were characterized by a high mortality rate among the studied groups of snails. Based on the collected research results, it was found that plant alkaloids can be extremely useful in the fight against problematic species of snails and cause much lower harm to the environment than synthetic molluscicides.

Evaluation of molluscicidal activity on Biomphalaria glabrata (Say, 1818) and phytochemical characterization of hydroalcoholic extract of leaves of Ricinus communis L. (EUPHORBIACEAE).

Schistosomiasis is a parasitic infection of great prevalence worldwide, affecting 250 million people in 78 countries. Faced with this problem, studies that seek to analyze molluscicidal activity from plant extracts have stood out. The present work aimed to obtain the phytochemical characterization and investigate the molluscicidal activity in the hydroalcoholic extract of Ricinus communis leaves on Biomphalaria glabrata. The hydroalcoholic extract was prepared by macerated with solvent ethanol P.A 96%, followed by filtration and concentration in rotary evaporator. Next, five groups of snails with 10 animals each, one being the negative control group, were submitted to treatments with four concentrations of 25, 50, 75 and 100 mg/L of hydroalcoholic extract of R. communis. The parameters mortality, physiological and behavioral aspects of mollusks were analyzed during 96h. The chemical characterization of the extract was performed by high-performance liquid chromatography coupled to mass spectrometry (LC-MS). Chemical characterization revealed the presence of tannins, flavonoids and ricinin alkaloid, but under the conditions analyzed, the presence of saponins was not observed. There was no significant molluscicidal activity of the extract. However, a greater influence was observed in the diet, in addition to the motility and physiological state of the snails (alteration of cephalopodal mass and oviposition). The toxicity test was performed with Artemia salina and no toxicity was observed for this microcrustacean. It is expected that the results obtained contribute to the fight against the expansion of schistosomiasis and that they make room for other studies that investigate the molluscicidal action of plant extracts.

Molluscicidal and biochemical effects of green-synthesized F-doped ZnO nanoparticles against land snail Monacha cartusiana under laboratory and field conditions.

The glass clover snail, Monacha cartusiana (M. cartusiana) is one of the most seriously impacting economic animal pests spreading across Egypt which inflicts severe damages to the agriculture. A green route is developed by deploying an abundant Rosemary plant leaves aqueous extract to synthesize ZnO and F-doped ZnO (F-ZnO) nanoparticles (NPs) that display high molluscicidal activities against the M. cartusiana land snails via leaf dipping and contact techniques. The effect of lethal concentrations, that kills 50% of exposed snails (LC50) value of the treatments, is examined on the activity of alkaline phosphatase (ALP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), enzymes, total protein (TP), total lipids (TL) and cholesterol level of snails, including the histopathological evaluation of the digestive gland and foot of M. Cartusiana. Their molluscicidal activity as poisonous baits under field conditions is also evaluated and compared to the recommended molluscicide, Neomyl. The results show that F- doping dramatically improves the snail control capability of ZnO NPs, and promotes a considerable increase in both ALT and AST enzymes with an enhancement of TL and Cholesterol levels, but a significant decrease in TP content and ALP activity in treated snails compared to the control group. The LC50 values are found to be 1381.55 and 2197.59 ppm using the leaf dipping for F-ZnO and ZnO, while 237.51 and 245.90 ppm can be achieved using the contact technique, respectively. The greenly synthesized F-ZnO and ZnO NPs induce severe histological alterations in the digestive gland and foot of M. cartusiana, including a complete destruction of the digestive tubules. The histological evaluation of the foot of M. cartusiana exposed to ZnO, shows a rupture of the epithelial layer of the foot sole, while F- ZnO NPs causes the folds of the foot becoming deeper and the rupture of epithelial layer. Our field experiments further demonstrate that F-ZnO achieves 60.08% reduction, while ZnO attains 56.39% diminution in snail population compared to the commercial, Neomyl (69.55%), exhibiting great potentials in controlling the harmful land snail populations.

Immunotoxical, neurotoxical, histopathological and immunohistopathological alterations of Nerium oleander and Tecoma stans methanolic extract on Biomphalaria alexandrina snails.

Schistosomiasis is a severe illness that caused socioeconomic problems. The present study aimed to investigate the molluscicidal activities of the methanolic extract of Nerium oleander and Tecoma stans on B. alexandrina snails. The present results showed that N. oleander had the higher molluscicidal effect (LC50: 138.6 mg/l) than T. stans methanolic extract (LC50: 256.0 mg/l). These concentrations had no mortality effects on Daphnia magna during the first 12 h of the exposure, while, they had a cercaricidal activity. Exposure of B. alexandrina snails to the sub lethal concentrations (LC10 and LC25) of the methanolic extract of either N. oleander or T. stans caused a concentration- dependent significant decrease in their mean total number of hemocyte and hyalinocytes percent, while, both the round small and the granulocytes were increased than the control group. Exposure of B. alexandrina snails to LC25 of the methanolic extract of N. oleander or T. stans, caused morphological alterations in the hemocytes that were studied by both light and electron microscopy. The sub lethal concentration (LC25) significantly decreased the acetyl cholinesterase activities, acid and alkaline phosphatase levels and the protein content. Histopathological changes occurred in the digestive and the hermaphrodite glands of exposed B. alexandrina snails to LC25 of the methanolic extracts. These alterations were confirmed by Immunohistochemistry for PCNA and Cyclin D1 expressions. Conclusively, these plants could be used to decrease the spread of schistosomiasis as they are cheap and environmentally safe to replace the synthetic molluscicides for snail control.

Toxic, cytotoxic and genotoxic effect of saline extract and fraction of Parkia pendula seeds in the developmental stages of Biomphalaria glabrata (Say 1818 - intermediate host) and cercaricide activity against the infectious agent of schistosomiasis.

This study describes for the first time the effect of saline extract and Parkia pendula seed fraction on Biomphalaria glabrata adult embryos and molluscs well as the reproductive parameters (fecundity and fertility) and survival, in addition to cytotoxicity and genotoxicity through the profile of blood cells after exposure to sublethal concentrations. Furthermore, we analyzed the action of both preparations against the cercariae of Schistosoma mansoni and their environmental safety using the bioindicator Artemia salina. The saline extract and fraction showed toxic effects for embryos (CL90 of 464.25, 479.62, 731.28, 643.28, 408.43 and 250.94, 318.03, 406.12, 635.64, 1.145 mg/mL, for blastula, gastrula, trocophore, veliger and hippo stage respectively), adult snails after 24 h of exposure (CL90 of 9.50 and 10.92 mg/mL, respectively) with increased mortality after 7 days of observation and significant decrease (p <0.05; p < 0.01 and p < 0.001) in egg mass deposition. At sublethal concentrations, an increase in quantitative and morphological changes in hemocytes was observed, and in the genotoxicity/comet assay analysis, varying degrees of nuclear damage were detected. In addition, the saline extract showed changes in the motility of the cercariae, while the fraction howed toxicity from a concentration of 1.0 mg/mL. The saline extract showed toxicity to A. salina at the highest concentrations (3.0, 4.0 and 5.0 mg/mL), while the fraction did not show ecotoxicity. Thus, the saline extract and fraction was promising in combating schistosomiasis by eliminating the intermediate host and causing alterations and/or mortality to the infectious agent.

Chemical composition and effect of Dysphania ambrosioides (L.) mosyakin & clemants essential oil on Biomphalaria tenagophila (D'Orbigny, 1835).

Dysphania ambrosioides (L.) Mosyakin & Clemants, known as santa maria herb, is a medicinal plant used on pest control and to treat parasitic diseases. Due to its potential for pest control, the aim of this work was to determine the chemical composition of D. ambrosioides essential oil and evaluate its molluscicidal effect on Biomphalaria tenagophila, which is an intermediate host for the Schistosoma mansoni trematode, that is responsible for causing human schistosomiasis. The essential oil extracted from its leaves showed 87% of (Z)-ascaridole and 100% of mortality against B. tenagophila at 10 ppm after 24 h of experiment. LC50 and LC90 values were, respectively, 2.40 (1.90-2.99) ppm and 8.75 (6.39-14.12) ppm. D. ambrosioides essential oil proved to be a promising natural molluscicide against schistosomiasis when compared with commercial products.

Toxic effect of Croton rudolphianus leaf essential oil against Biomphalaria glabrata, Schistosoma mansoni cercariae and Artemia salina.

This research investigated the effect of the Croton rudolphianus leaf essential oil (EO) on Biomphalaria glabrata embryos (at different development stages) and adults, Schistosoma mansoni cercariae, and Artemia salina (non-target organism). It was possible to identify 31 compounds in the C. rudolphianus EO through GC-MS analysis. The major compounds from this oil were (E)-caryophyllene (17.33%), an unknown compound (16.87%), bicyclogermacrene (7.1%), δ-cadinene (6.62%) and germacrene D (5.38%). After incubation for 24 h, the EO of C. rudolphianus induced the occurrence of non-viable embryos (dead and malformed), with an LC50 value of 126.54, 133.51, 143.53 and 161.95 µg/mL and an LC90 value of 202.61, 216.48, 232.98 and 271.16 µg/mL to blastula, gastrula, trochophore and veliger embryonic stages, respectively. The EO was more effective against B. glabrata adults (LC50 and LC90 = 47.89 and 78.86 µg/mL, respectively), and S. mansoni cercariae (LC50 and LC90 = 14.81 and 22.15 after 120 mins of exposure, respectively) than against B. glabrata embryos. Concerning the micronucleus assay, the mean frequency of apoptosis, binucleation and micronucleus were 45.33 ± 3.51, 19.33 ± 1.53 and 0.67 ± 0.58 per 1000 cells at 25 µg/mL, which is the highest concentration tested. The oil killed A. salina with LC50 and LC90 values (68.33 and 111.5 µg/mL, respectively) higher than those determined for adult snails and S. mansoni cercariae. In conclusion, C. rudolphianus EO had a toxic effect against B. glabrata adults and embryos, and S. mansoni cercariae. Furthermore, this oil showed to be cytotoxic to hemocytes of B. glabrata. Concerning the non-target organism assay, C. rudolphianus EO was less toxic to A. salina then to adult snails and S. mansoni cercariae. Due to this, the EO from C. rudolphianus leaves is a potential alternative for schistosomiasis control.

[Molluscicidal activity of the Bacillus velezensisis Y6 strain against Oncomelania hupensis and its preliminary mechanisms of molluscicidal actions].

OBJECTIVE: To assess the molluscicidal activity of the of Bacillus Y6 strain against Oncomelania hupensis in laboratory, and to preliminarily investigate its mechanisms of molluscicidal actions. METHODS: Biological identification of the Y6 strain was performed based on analysis of its morphological and physiochemical features and homology analysis of the 16S rDNA gene sequence. Bacillus Y6 suspensions were formulated at concentrations of 0.005, 0.010 g/mL and 0.015 g/mL, and the molluscicidal activity of Bacillus Y6 suspensions against O. hupensis was tested in laboratory using the immersion method. In addition, the Bacillus Y6 content and glycogen content were detected in O. hupensis following exposure to Bacillus Y6 suspensions to preliminarily explore the molluscicidal mechanism of the Bacillus Y6 strain against O. hupensis. RESULTS: The colony of the Bacillus Y6 strain appeared non-transparent milky white, and mycoderma was produced on the surface of the nutrient agar liquid medium. The Y6 stain was Gram positive and rod-shaped, and the endospore was located at the center of the Bacillus Y6 strain and appeared an achromatic, transparent and refractive body, which was encapsulated by the Y6 strain. The Y6 strain was positive for the lecithinase test, and the 16S rDNA gene sequence showed a 100% homology with those of multiple B. velezensisis strains, B. amyloliquefaciens and B. subtilis. The Y6 strain was therefore identified as B. velezensisis. Following immersion in the Bacillus Y6 suspensions at concentrations of 0.005, 0.010 g/mL and 0.015 g/mL for 24, 48 h and 72 h, the mortality rates of Oncomelania snails were 28.3%, 31.7% and 81.6%, 43.3%, 58.3% and 93.3%, and 63.3%, 78.3% and 98.3%, respectively. The molluscicidal activity of the Bacillus Y6 suspensions increased with the suspension concentration and duration of immersion. Microscopy and colony counting revealed the highest Y6 content in dead snails and the lowest in living snails following immersion in Bacillus Y6 suspensions, and the mean glycogen contents were (0.68 ± 0.06), (1.09 ± 0.16) µg/mg and (2.56 ± 0.32) µg/mg in the soft tissues of dead, dying and living snails following immersion in Bacillus Y6 suspensions (F = 59.519, P < 0.05), and the mean glycogen content was significantly higher in living snails than in dead (t = 14.073, P < 0.05) and dying snails (t = 10.027, P < 0.05), while the mean glycogen content was significantly higher in dying snails than in dead snails (t = 5.983, P < 0.05). CONCLUSIONS: The B. velezensisis Y6 strain shows a high molluscicidal activity against O. hupensis snails, and its invasion may cause glycogen metabolism disorders, leading to snail death.

Lantana camara Essential Oils from Vietnam: Chemical Composition, Molluscicidal, and Mosquito Larvicidal Activity.

Lantana camara is a troublesome invasive plant introduced to many tropical regions, including Southeast Asia. However, the plant does hold promise as a source of essential oils that may be explored for potential use. Fresh water snails such as Pomacea canaliculata, Gyraulus convexiusculus, and Tarebia granifera can be problematic agricultural pests as well as hosts for parasitic worms. Aedes and Culex mosquitoes are notorious vectors of numerous viral pathogens. Control of these vectors is of utmost importance. In this work, the essential oil compositions, molluscicidal, and mosquito larvicidal activities of four collections of L. camara from north-central Vietnam have been investigated. The sesquiterpene-rich L. camara essential oils showed wide variation in their compositions, not only compared to essential oils from other geographical locations (at least six possible chemotypes), but also between the four samples from Vietnam. L. camara essential oils showed molluscicidal activities comparable to the positive control, tea saponin, as well as other botanical agents. The median lethal concentrations (LC50 ) against the snails were 23.6-40.2 µg/mL (P. canaliculata), 7.9-29.6 µg/mL (G. convexiusculus), and 15.0-29.6 µg/mL (T. granifera). The essential oils showed good mosquito larvicidal activities with 24-h LC50 values of 15.1-29.0 µg/mL, 26.4-53.8 µg/mL, and 20.8-59.3 µg/mL against Ae. aegypti, Ae. albopictus, and Cx. quinquefasciatus, respectively. The essential oils were more toxic to snails and mosquito larvae than they were to the non-target water bug, Diplonychus rusticus (24-h LC50 =103.7-162.5 µg/mL). Sesquiterpene components of the essential oils may be acting as acetylcholinesterase (AChE) inhibitors. These results suggest that the invasive plant, L. camara, may be a renewable botanical pesticidal agent.

Molluscicidal activity of Persea americana Mill. (Lauraceae) stem bark ethanolic extract against the snail Biomphalaria glabrata (Say, 1818): a novel plant-derived molluscicide?

Plant-derived molluscicides have been indicated as biodegradable and low-cost strategies for control of Biomphalaria spp., intermediate host for the Schistosoma. This study evaluated whether the crude ethanolic extract of the Persea americana stem bark has molluscicidal activity against embryos, newly-hatched and adults of Biomphalaria glabrata. The extract was obtained, characterized and its toxicity analyzed by snail embryotoxicity test (144 h) and acute toxicity test with newly-hatching and adult snails (96 h). Results showed the presence of flavonoids, anthraquinone heterosides, coumarins and tannins in the crude ethanolic extract, which showed molluscicidal activity against all life cycle stages of B. glabrata. The LC50 for embryos, newly-hatched and adults were 27.06, 30.60 and 55.55 ppm, respectively. Embryos exposed to the extract at 50 ppm showed hatching inhibition and at 6.2 and 25 ppm had the highest rates of morphological alterations, such as shell malformations and coagulation of the perivitelline substance. Adult snails exposed to the extract at 75 ppm showed a peak of behavioral changes, such as lethargy and shell reclusion, in addition to answers like hemolymph release in most concentrations. Further studies are required, prioritizing toxicity testing on non-target organisms and further elucidation of the active molecules.

Molluscicidal and parasiticidal activities of Eryngium triquetrum essential oil on Schistosoma mansoni and its intermediate snail host Biomphalaria glabrata, a double impact.

BACKGROUND: Freshwater snails are the intermediate hosts of a large variety of trematode flukes such as Schistosoma mansoni responsible for one of the most important parasitic diseases caused by helminths, affecting 67 million people worldwide. Recently, the WHO Global Vector Control Response 2017-2030 (GVCR) programme reinforced its message for safer molluscicides as part of required strategies to strengthen vector control worldwide. Here, we present the essential oil from Eryngium triquetrum as a powerful product with molluscicide and parasiticide effect against S. mansoni and the snail intermediate host Biomphalaria glabrata. METHODS: In the present study, we describe using several experimental approaches, the chemical composition of E. triquetrum essential oil extract and its biological effects against the snail B. glabrata and its parasite S. mansoni. Vector and the free-swimming larval stages of the parasite were exposed to different oil concentrations to determine the lethal concentration required to produce a mortality of 50% (LC50) and 90% (LC90). In addition, toxic activity of this essential oil was analyzed against embryos of B. glabrata snails by monitoring egg hatching and snail development. Also, short-time exposure to sublethal molluscicide concentrations on S. mansoni miracidia was performed to test a potential effect on parasite infectivity on snails. Mortality of miracidia and cercariae of S. mansoni is complete for 5, 1 and 0.5 ppm of oil extract after 1 and 4 h exposure. RESULTS: The major chemical component found in E. triquetrum oil determined by GC-FID and GC/MS analyses is an aliphatic polyacetylene molecule, the falcarinol with 86.9-93.1% of the total composition. The LC50 and LC90 values for uninfected snails were 0.61 and 1.02 ppm respectively for 24 h exposure. At 0.5 ppm, the essential oil was two times more toxic to parasitized snails with a mortality rate of 88.8 ± 4.8%. Moderate embryonic lethal effects were observed at the concentration of 1 ppm. Severe surface damage in miracidia was observed with a general loss of cilia that probably cause their immobility. Miracidia exposed 30 min to low concentration of plant extract (0.1 ppm) were less infective with 3.3% of prevalence compare to untreated with a prevalence of 44%. CONCLUSIONS: Essential oil extracted from E. triquetrum and falcarinol must be considered as a promising product for the development of new interventions for schistosomiasis control and could proceed to be tested on Phase II according to the WHO requirements.

Molluscicidal activity and physiological toxicity of quaternary benzo[c]phenanthridine alkaloids (QBAs) from Macleaya cordata fruits on Oncomelania hupensis.

Schistosomiasis is a serious worldwide parasitic disease. One of the best ways to control schistosomiasis is to control the population of Oncomelania hupensis snails. We sought to identify a high-efficiency biogenic molluscicide against Oncomelania with low toxicity, to avoid chemical molluscicide contamination and toxicity in aquatic organisms. We extracted quaternary benzo[c]phenanthridine alkaloids (QBAs) from Macleaya cordata fruits. Molluscicidal activity of the QBAs against Oncomelania was determined using bioassay. Our results showed that the extracted QBAs had a strong molluscicidal effect. In treatment of O. hupensis with QBAs for 48 h and 72 h, the lethal concentration (LC50) was 2.89 mg/L and 1.29 mg/L, respectively. The molluscicidal activity of QBAs was close to that of niclosamide (ethanolamine salt), indicating that QBAs have potential development value as novel biogenic molluscicides. We also analyzed physiological toxicity mechanisms by examining the activity of several important detoxification enzymes. We measured the effect of the extracted QBAs on the activities of glutathione S-transferase (GST), carboxylesterase (CarE), acid phosphatase (ACP), and alkaline phosphatase (AKP) in the liver of O. hupensis. We found that the effects of QBAs on detoxification metabolism in O. hupensis were time and concentration dependent. The activities of GST, CarE, AKP, and ACP in the liver of snails increased significantly in the early stage of treatment (24 h), but decreased sharply in later stages (120 h), compared with these activities in controls. GST, CarE, AKP, and ACP activity in the liver of snails treated with LC50 QBAs for 120 h decreased by 62.3%, 78.1%, 59.2%, and 68.6%, respectively. Our results indicate that these enzymes were seriously inhibited by the extracted QBAs and the detoxification and metabolic functions of the liver gradually weakened, leading to poisoning, which could be the main cause of death in O. hupensis snails.

Assessment of the molluscicidal impact of extracted chlorophyllin on some biochemical parameters in the nervous tissue and histological changes in Biomphalaria alexandrina and Lymnaea natalensis snails.

Biomphalaria alexandrina and Lymnaea natalensis snails are the intermediate hosts of schistosomiasis and fasciolosis. The aim of the present study is to evaluate the molluscicidal activity of chlorophyll extract as a photodynamic substance against these snails and how it affected its tissues and the biological system. Chlorophyllin was extracted from deep-frozen Moringa oleifera leaves, and then it was transformed into water-soluble chlorophyllin. The present results showed that it had a molluscicidal activity on B. alexandrina snails (LC50 17.6 mg/l; LC90 20.9 mg/l) and L. natalensis snails (LC50 4.3 mg/l; LC90 6.8 mg/l). Exposing B. alexandrina snails to the sublethal concentrations (LC0, LC10, and LC25) resulted in a significant reduction in their survival rates. Regarding its effect on biochemical parameters, chlorophyllin significantly reduced the acetylcholinesterase activity, protein content, and alkaline and acid phosphatase activity in B. alexandrina nervous tissue compared to the control group. Histopathological changes occurred in the digestive gland of treated B. alexandrina snails where cells lost their nuclei, vacuolated, degenerated, and ruptured, and the lumen increased. Photosynthesizing materials like chlorophyllin are new approaches to control schistosomiasis and fasciolosis in developing countries by affecting their intermediate host. These materials were cheap and environmentally safe to replace the synthetic molluscicides for snail control.

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

BACKGROUND: 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. METHODS: 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). RESULTS: 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 [corrected] 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). CONCLUSIONS: 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.

Molluscicidal activity of cardiac glycosides isolated from Adenium obesum.

BACKGROUND: Terrestrial mollusks are one of most important agricultural pests worldwide. Natural phytochemicals have an extended history as a source of pesticides. This study was planned to isolate molluscicidal active compounds from the stems of Adenium obesum. RESULTS: The benzene-soluble fraction of the hydroethanolic extract displayed the most potent molluscicidal activity against Monacha obstructa among different solvent fractions with a median lethal dose (LD50 ) of 4.91 µg g-1 body weight (bw). The bioactivity-guided chemical exploration of the benzene-soluble fraction led to the isolation of two known cardiac glycosides, cerberin and neriifolin which showed significant molluscicidal activity with LD50 values of 5.39 and 4.3 µg g-1 bw, respectively. CONCLUSION: Isolation of the cardiac glycoside neriifolin from A. obesum and the molluscicidal activity of cerberin and neriifolin against terrestrial snails are reported for the first time. © 2019 Society of Chemical Industry.

A Pilot Evaluation of the Toxicity of EarthTec® QZ on Invasive (Bithynia tentaculata) and Native (Physa gyrina) Snail Species from the Upper Mississippi River.

We used a comparative approach to investigate the effects of a copper-based pesticide (EarthTec® QZ) on embryos of an invasive snail (Bithynia tentaculata) and a native snail (Physa gyrina). Embryos were exposed to one of three treatments: control (0 mg/L Cu2+), low-dose (0.1 mg/L Cu2+), or high-dose (0.6 mg/L Cu2+), which reflect manufacturer-recommended low and medium 4-day molluscicide treatment concentrations. Exposure to 0.6 mg/L Cu2+ over 4 days generated 100% mortality in both invasive and native snail embryos; however, reducing the exposure time from 4 to 1 day resulted in 100% mortality in B. tentaculata but some hatching (7%) in P. gyrina. In contrast, embryos of both species exposed to 0.1 mg/L Cu2+ treatment for 4 days showed almost 100% survivorship. Further manipulations of Cu2+ concentrations and exposure times may yield regimes that maximize mortality in B. tentaculata while minimizing negative impacts on native species.

Molluscicidal activity of Solidago canadensis L. extracts on the snail Pomacea canaliculata Lam.

Extracts from the aerial parts of Solidago canadensis L. were evaluated for molluscicidal activity against Pomacea canaliculata Lam. using an immersion bioassay method. The petroleum ether fraction of the ethanolic extract (PEEE) from S. canadensis exhibited strong molluscicidal activity. The PEEE mode of action in the hepatopancreas tissue of P. canaliculata was tested at several concentrations. Biochemical parameters, namely, soluble sugar content, protein, malondialdehyde (MDA), acetylcholinesterase (AChE) activity, alanine aminotransferase (ALT), and aspartate transaminase (AST) were significantly decreased or increased after exposure to PEEE for 48 h (p<0.05). Histological assessment results showed that hepatopancreas tissue structure was destroyed by exposure to PEEE. Gas chromatography-mass spectrometry analysis (GC-MS) was used to identify 15 compounds that could contribute to the molluscicidal efficacy of the PEEE. Molluscicidal assay, biochemical tests and histological assessments suggest that the PEEE from S. canadensis has potential utility as a molluscicide.