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@#The spraying of insecticide on foliage to provide an insecticidal barrier may serve as part of the vector control measures to combat the increasing threat of Aedes-borne diseases. The effectiveness of insecticide barrier spraying was evaluated by assessing the residual efficacy of deltamethrin sprayed on foliage against Malaysian Ae. aegypti (L.) and Ae. albopictus (Skuse). In this semi-field study, landscape plants grown within the vicinity of the Institute for Medical Research (IMR), Malaysia, were treated with deltamethrin suspension concentrate (SC) with the dosage of 30 mg/m2 and 50 mg/m2 in three rounds of spraying. Deltamethrin residual activity on treated and untreated leaves was investigated using standard WHO cone bioassays. Wild Aedes populations at both deltamethrin-treated and untreated plant clusters were monitored by ovitrap surveillance. Ovitrap monitoring revealed that the mean number of Ae. albopictus larvae at deltamethrin-treated were significantly lower than the mean number of larvae of the same species at the untreated plant cluster. Cone bioassay results showed that the insecticide remained effective for up to 4 weeks (> 80% mortality), but the insecticide residual activity was affected by rainfall. These results suggest that insecticide barrier spraying is a promising tool and may be used along with other mosquito control tools such as indoor residual spray and space spraying to reduce the dengue burden.
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Objective To investigate the effectiveness and cost of 50% and 80% wettable powder of niclosamide ethanolamine salt (NESWP) and 26% metaldehyde and niclosamide suspension concentrate (MNSC) in hilly schistosomiasis-endemic regions, so as to provide insights into the selection of chemical molluscicides in hilly regions. Methods In September 2020, a wasteland in Guanshanqiao Village, Yanrui Township, Yushan County of Jiangxi Province was selected as the experimental region, which was sectioned into five blocks and defined as four experimental groups (A1, A2, B, C) and a blank control group (D). 80% NESWP were given at doses of 1 g/m2 and 1.5 g/m2 in groups A1 and A2 using the spraying method, 50% NESWP was given at a dose of 2 g/m2 in Group B using the spraying method, and 26% MNSC was at a dose of 4 g/m2 in Group C using the spraying method, while no chemical treatment was given in Group D. Snail survey was performed using a systematic sampling method before chemical treatment and 1, 3, 7 d and 15 d post-treatment to examine the molluscicidal effect, and all molluscicidal costs were estimated to calculate the cost of chemical treatment per 1 m2 and the cost of the reduction in the mean density of living snails per 1%. Results The highest mortality of snails was 78.95% and the lowest density of living snails was 0.2388 snails/0.1 m2 in the experimental groups within 7 d of chemical treatment, and the highest mortality of snails was 94.74% and the lowest density of living snails was 0.058 0 snails/0.1 m2 7 d post-treatment. There were no significant differences in the snail mortality among the A1, A2, B and C groups 1 (χ2 = 2.250, P > 0.05), 3 (χ2 = 1.779, P > 0.05) or 15 d post-treatment (χ2 = 2.286, P > 0.05), while a significant difference was detected in the snail mortality among the four groups 7 d post-treatment (χ2 = 7.990, P = 0.046). In addition, there were no significant differences in the snail mortality between A1 and A2 groups 1 (χ2 = 0.724, P > 0.05), 3 (χ2 = 0.584, P > 0.05), 7 (χ2 = 0.400, P > 0.05) or 15 d post-treatment (χ2 = 0.251, P > 0.05). The costs of chemical treatment per 1 m2 were 0.58, 0.60, 0.64 Yuan and 0.73 Yuan in groups A1, A2, B and C, and the costs of the mean density of living snail per 1% reduction were 19.29, 20.44, 21.68 Yuan and 23.53 Yuan in groups A1, A2, B and C, respectively. Conclusion 80% NESWP shows a high molluscicidal efficacy and low cost in hilly schistosomiasis-endemic regions.
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Objective To compare the molluscicidal effects and cost-effectiveness of 5% niclosamide ethanolamine salt granules (NEG) and 26% suspension concentrate of metalaldehyde and niclosamide ethanolamine salt (MNSC) . Methods Two plots with high Oncomelania hupensis snail density were selected as research areas in Nanjing Chemical Industry Zone, and 5% NEG (40 g/m2) and 26% MNSC (40 g/m2) were used by the spraying method for snail control in the two plots, and their molluscicidal effects and cost-effectiveness were investigated and statistically analyzed. Results There was no significant difference between 5% NEG and 26% MNSC in the molluscicidal effects. The cost of 5% NEG was 1.25 times higher than that of 26% MN-SC per ten thousand square meters in snail control. Conclusions The cost of 5% NEG is higher than that of 26% MNSC per ten thousand square meters in snail control. Their molluscicidal effects are similar.
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Objective To compare the effectiveness of snail control between immersion of molluscicides through tide diversion and mollusciciding by spraying in marshland areas. Methods Immersion of 26% suspension concentrate of metaldehyde and niclosamide through tide diversion and spraying 26% suspension concentrate of metaldehyde and niclosamide alone were employed for snail control in two neighboring snail-breeding marshlands, and snails were surveyed before and after mollusciciding. The mortality of snails and the density of living snails were estimated. Results The density of living snails reduced by 72.19% and 100.00% 1 and 2 years after immersion of 26% suspension concentrate of metaldehyde and niclosamide through tide diversion, and 5.93% and 18.15% 1 and 2 years after spraying 26% suspension concentrate of metaldehyde and niclosamide alone. Conclusion Immersion of 26% suspension concentrate of metaldehyde and niclosamide through tide diversion is significantly superior to spraying 26% suspension concentrate of metaldehyde and niclosamide along for snail control, and implementation of immersion of 26% suspension concentrate of metaldehyde and niclosamide through tide diversion for more than 2 successive years may achieve a higher snail control efficiency.
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Objective To evaluate the effect and cost-effectiveness of three commonly used molluscicides, 4% "Luo-wei" (tea-seed distilled saponins, TDS), 50% niclosamide ethanolamine salt wettable powder (NESWP), and 26% metaldehyde and niclosamide suspension concentrate (MNSC) in large-scale field application, so as to provide the references for formulating the strategy of snail control. Methods The field test and parallel comparison were implemented. A marshland with Oncomelania hupensis snails of the Yangtze River was divided into 4 parts (10 hm2) for the research, and three of them were experimental areas while the last one was a blank control area. The experimental areas were sprayed with 4% "Luo-wei", 50% NESWP and 26% MNSC respectively for 3 times and the interval was 1 week. Seven days after each spraying the effect of snail control was investigated, and the costs of molluscicides, labor, transportation, fuel consumption and mechanical loss were recorded. The cost of each molluscicide, snail mortality, snail density, and the cost of increasing 1% of snail mortality per 100 m2 were analyzed and compared. Results After the first, second and third spraying, the corrected snail mortality rates were 67.34%, 76.55% and 84.60% respectively in the 4% "Luo-wei" group; the corrected snail mortality rates were 64.71%, 75.17% and 83.89% respectively in the 50% NESWP group; the corrected snail mortality rates were 66.55%, 76.27% and 86.67% respectively in the 26% MNSC group. There was no significant difference among the 3 groups in the snail mortality at the same spraying time (χ2 = 1.590, 0.571, 3.238, all P > 0.05) . In addition, along with the increase of the spraying times, the snail mortality of each group was increased significantly compared to that of the control group (χ2 = 79.333, 94.718, 117.020, all P < 0.01) . After the first, second and third spraying, the reduction rates of snail density were 69.82%–86.60% in the 4% "Luo-wei" group, 68.66%–86.55% in the 50% NESWP group, and 71.89%–88.87% in the 26% MNSC group respectively. The decreasing amplitude of the snail density was more than 85% in all the experimental areas after 3 rounds of spraying molluscicide. The snail control costs per 100 hm2 were 19.57, 11.97 Yuan and 10.47 Yuan in the 4% "Luo-wei" group, 50% NESWP group, and 26% MNSC group respectively. After the first, second and third spraying, the costs of increasing 1% of snail mortality per 100 m2 were 0.30, 2.08 Yuan and 2.38 Yuan in the 4% "Luo-wei" group, 0.20, 1.10 Yuan and 1.32 Yuan in the 50% NESWP group, and 0.17, 1.04 Yuan and 0.97 Yuan in the 26% MNSC group respectively, and the cost-effectiveness was the highest at the first spraying in all the three groups. Conclusions The effects of the three molluscicides for snail control are similar, but the efficacy of snail control is reduced as the spraying time increases.
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Objective To compare the effectiveness of snail control between immersion of molluscicides through tide diversion and mollusciciding by spraying in marshland areas. Methods Immersion of 26% suspension concentrate of metaldehyde and niclosamide through tide diversion and spraying 26% suspension concentrate of metaldehyde and niclosamide alone were employed for snail control in two neighboring snail-breeding marshlands, and snails were surveyed before and after mollusciciding. The mortality of snails and the density of living snails were estimated. Results The density of living snails reduced by 72.19% and 100.00% 1 and 2 years after immersion of 26% suspension concentrate of metaldehyde and niclosamide through tide diversion, and 5.93% and 18.15% 1 and 2 years after spraying 26% suspension concentrate of metaldehyde and niclosamide alone. Conclusion Immersion of 26% suspension concentrate of metaldehyde and niclosamide through tide diversion is significantly superior to spraying 26% suspension concentrate of metaldehyde and niclosamide along for snail control, and implementation of immersion of 26% suspension concentrate of metaldehyde and niclosamide through tide diversion for more than 2 successive years may achieve a higher snail control efficiency.
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Objective To evaluate the effect and cost-effectiveness of three commonly used molluscicides, 4% "Luo-wei" (tea-seed distilled saponins, TDS), 50% niclosamide ethanolamine salt wettable powder (NESWP), and 26% metaldehyde and niclosamide suspension concentrate (MNSC) in large-scale field application, so as to provide the references for formulating the strategy of snail control. Methods The field test and parallel comparison were implemented. A marshland with Oncomelania hupensis snails of the Yangtze River was divided into 4 parts (10 hm2) for the research, and three of them were experimental areas while the last one was a blank control area. The experimental areas were sprayed with 4% "Luo-wei", 50% NESWP and 26% MNSC respectively for 3 times and the interval was 1 week. Seven days after each spraying the effect of snail control was investigated, and the costs of molluscicides, labor, transportation, fuel consumption and mechanical loss were recorded. The cost of each molluscicide, snail mortality, snail density, and the cost of increasing 1% of snail mortality per 100 m2 were analyzed and compared. Results After the first, second and third spraying, the corrected snail mortality rates were 67.34%, 76.55% and 84.60% respectively in the 4% "Luo-wei" group; the corrected snail mortality rates were 64.71%, 75.17% and 83.89% respectively in the 50% NESWP group; the corrected snail mortality rates were 66.55%, 76.27% and 86.67% respectively in the 26% MNSC group. There was no significant difference among the 3 groups in the snail mortality at the same spraying time (χ2 = 1.590, 0.571, 3.238, all P > 0.05) . In addition, along with the increase of the spraying times, the snail mortality of each group was increased significantly compared to that of the control group (χ2 = 79.333, 94.718, 117.020, all P < 0.01) . After the first, second and third spraying, the reduction rates of snail density were 69.82%–86.60% in the 4% "Luo-wei" group, 68.66%–86.55% in the 50% NESWP group, and 71.89%–88.87% in the 26% MNSC group respectively. The decreasing amplitude of the snail density was more than 85% in all the experimental areas after 3 rounds of spraying molluscicide. The snail control costs per 100 hm2 were 19.57, 11.97 Yuan and 10.47 Yuan in the 4% "Luo-wei" group, 50% NESWP group, and 26% MNSC group respectively. After the first, second and third spraying, the costs of increasing 1% of snail mortality per 100 m2 were 0.30, 2.08 Yuan and 2.38 Yuan in the 4% "Luo-wei" group, 0.20, 1.10 Yuan and 1.32 Yuan in the 50% NESWP group, and 0.17, 1.04 Yuan and 0.97 Yuan in the 26% MNSC group respectively, and the cost-effectiveness was the highest at the first spraying in all the three groups. Conclusions The effects of the three molluscicides for snail control are similar, but the efficacy of snail control is reduced as the spraying time increases.
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Objective To evaluate the molluscicidal effects of different formulations of niclosamide ethanolamine salt in marshlands. Methods The molluscicidal effects of spraying with 25% suspension concentrate of niclosamide ethanolamine salt (25% SCN) and 50% wettable powder formulation of niclosamide ethanolamine salt (50% WPN), and dusting with 4% niclosamide ethanolamine salt dustable powder (4% DP) for controlling Oncomelania hupensis snails were investigated and compared in the fields, and the cost-effectiveness was analyzed. Results The corrected mortalities and the reduced rates of density of snails were 54.37%, 91.70%, 92.76%, 79.50%, and 59.55%, 95.93%, 97.63%, 94.15%, respectively, on 3, 7, 15, 30 d after spaying with 25% SCN, those on 3, 7, 15, 30 d after dusting with 4% DP were 59.10%, 91.83%, 95.56%, 93.34% and 65.03%, 94.93%, 97.61%, 97.28%, respectively; and those on 3, 7, 15, 30 d after spraying with 50% WPN were 76.29%, 91.68%, 93.12%, 81.59% and 81.24%, 97.02%, 97.84%, 95.27%, respectively. The cost of spraying with 25% SCN was 0.21 Yuan/m2, that of dusting with 4% DP was 0.39 Yuan/m2, and that of spraying with 50% WPN was 0.23 Yuan/m2 for snail control in the marshland. The cost of reduced one percentage of the corrected mortalities and the density of snails in controlling snails by 25% SCN, 4% DP and 50% WPN on 15 d were 22.68, 40.63, 25.17 Yuan and 21.54, 39.78, 23.95 Yuan, respectively. Conclusions The three different formulations of niclosamide are reliable and effective for snail control in marshlands. There are some differences among the different molluscicides in start time, pharmacodynamic characteristics, spraying methods in the field, cost of snail control, and influencing factors. Therefore, we need reasonably select the suitable molluscicides according to the environmental characteristics and working condition.
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Objective To evaluate the molluscicidal effects of different formulations of niclosamide ethanolamine salt in marshlands. Methods The molluscicidal effects of spraying with 25% suspension concentrate of niclosamide ethanolamine salt (25% SCN) and 50% wettable powder formulation of niclosamide ethanolamine salt (50% WPN), and dusting with 4% niclosamide ethanolamine salt dustable powder (4% DP) for controlling Oncomelania hupensis snails were investigated and compared in the fields, and the cost-effectiveness was analyzed. Results The corrected mortalities and the reduced rates of density of snails were 54.37%, 91.70%, 92.76%, 79.50%, and 59.55%, 95.93%, 97.63%, 94.15%, respectively, on 3, 7, 15, 30 d after spaying with 25% SCN, those on 3, 7, 15, 30 d after dusting with 4% DP were 59.10%, 91.83%, 95.56%, 93.34% and 65.03%, 94.93%, 97.61%, 97.28%, respectively; and those on 3, 7, 15, 30 d after spraying with 50% WPN were 76.29%, 91.68%, 93.12%, 81.59% and 81.24%, 97.02%, 97.84%, 95.27%, respectively. The cost of spraying with 25% SCN was 0.21 Yuan/m2, that of dusting with 4% DP was 0.39 Yuan/m2, and that of spraying with 50% WPN was 0.23 Yuan/m2 for snail control in the marshland. The cost of reduced one percentage of the corrected mortalities and the density of snails in controlling snails by 25% SCN, 4% DP and 50% WPN on 15 d were 22.68, 40.63, 25.17 Yuan and 21.54, 39.78, 23.95 Yuan, respectively. Conclusions The three different formulations of niclosamide are reliable and effective for snail control in marshlands. There are some differences among the different molluscicides in start time, pharmacodynamic characteristics, spraying methods in the field, cost of snail control, and influencing factors. Therefore, we need reasonably select the suitable molluscicides according to the environmental characteristics and working condition.
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Objective To compare the molluscicidal effects and cost-effectiveness of 5% niclosamide ethanolamine salt granules (NEG) and 26% suspension concentrate of metalaldehyde and niclosamide ethanolamine salt (MNSC) . Methods Two plots with high Oncomelania hupensis snail density were selected as research areas in Nanjing Chemical Industry Zone, and 5% NEG (40 g/m2) and 26% MNSC (40 g/m2) were used by the spraying method for snail control in the two plots, and their molluscicidal effects and cost-effectiveness were investigated and statistically analyzed. Results There was no significant difference between 5% NEG and 26% MNSC in the molluscicidal effects. The cost of 5% NEG was 1.25 times higher than that of 26% MN-SC per ten thousand square meters in snail control. Conclusions The cost of 5% NEG is higher than that of 26% MNSC per ten thousand square meters in snail control. Their molluscicidal effects are similar.
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Objective To evaluate the molluscicidal effect of suspension concentrate of niclosamide ethanolamine salt(SC-NE)against Oncomelania hupensis snails in laboratory and field. Methods The experiment of SCNE against the snails by using the immersing and spraying methods was performed in laboratory and field,with control groups of wettable powder of ni-closamide ethanolamine salt(WPN). Results In the laboratory,LC50(s) of SCNE for 24,48 h and 72 h by using the immersion method were 0.0926,0.0629 mg/L and 0.0549 mg/L,respectively. The mortality rates of snails for 24,48 h and 72 h by using the immersion method were all 100％ with the concentrations of 0.25 mg/L. The mortality rates of snails were all 100％ while spraying SCNE for 3 d in the laboratory with the concentrations of 0.25 g/m2. In Jiangling County,except 0.5 g/m3 SCNE immers-ing the snails for 24 h,the mortality rates of snails by using SCNE with the immersing method were all 100％. While the concen-tration of SCNE was 0.5 g/m3 or above,the mortality rates were all 100％after the use of it with the immersion method for 2 d in Gong'an County. In Jiangling County,the mortality rates of snails by using SCNE 0.5 g/m3 for 1 d,3 d,and 7 d with the spray-ing method were 87.5％,92.82％and 97.40％respectively. While the concentration of SCNE was 0.5 g/m3,the mortality rates were 85.94％,86.78％and 94.21％respectively after the use of it with the spraying method for 1 d,3 d,7 d in Gong'an Coun-ty,and the molluscicidal effect of SCNE(1.0 g/m2)was higher than that of WPN. Conclusion SCNE has a high molluscicidal effect in the laboratory and field,and it is a novel and simple formulation of niclosamide.
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Objective To compare the field molluscicidal effects of 25%suspension concentrate of nielosamide ethanolamine salt(SCNE),50% wettable powder of niclosamide ethanolamine salt(WPN),40% META-Li and 50% Rongbao powder,so as to provide scientific basis for choosing the safe and highly effective molluscicide in field.Methods Four snail habitats with the similar snail status were selected and sprayed with the four molluscicides mentioned above,respectively.Then the snail status in the four fields was surveyed 3,7 and 17 d after the spraying and the moiluscicidal effects of difierent molluscieides were cornpared.Results The corrected mortalities of snails in the field sprayed with SCNE 3,7 and 17 d afterthe spraying were the hiishest among the four fields,with the rates of 93.13%,91.85% and 85.28%,respectively.Conclusion SCNE has a high molluseieidal effect in the field and can be further used in snail-infested areas.
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Objective To evaluate the toxicity of suspension concentrate of niclosamide(SCN)for molluscicide in the field.Methods According to the state standard of the People's Republic of China "The methods of toxicity test for agriculture register",GB15670-1995,the experiments of acute toxicity on rats and fish were carried out.Results LD50(s)of SCN via mouth and skin with rats were more than 5 000 mg/kg respectively,and LC50(s)of SCN via inbreathe with rats were more than 5 000 mg/m3.Based on the classification of appraising criterion on acute toxicity test,it belonged to a feebleness toxicity degree.The eye and the skin stimulating tests with rabbits showed that it did not irritate the eyes and the skin.For fish,its acute toxicity was slightly lower than that of pure niclosamide,and markedly lower than that of pure niclosamide ethanolamine salt and WPN.Conclusions SCN belongs to a feebleness toxicity degree and has a lower toxicity to fish.It should be a useful molluscicide in endemic areas of schistosomiasis.
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Objective To observe the influence of suspension concentrate of niclosamide on the enzyme activity of Oncomelania hupensis in order to explore its molluscicidal mechanism. Methods Oncomelania hupensis snails were collected in the habitates of river marshland in Dantu District, Zhenjiang City, Jiangsu Provence and were divided into 2 groups. The snails of the treated group were sprinkled with 25% suspension concentrate of niclosamide. The snails of the control group were sprinkled with distilled water. The soft body tissue of the snail was separated and the sections of snail tissue were made in the Cryostat Microtome. The stain of enzyme-histochemistry showed CCO, LDH, SDH, CHE and NOS had been done, and then the staining block was made by routine method. The staining reaction in the snail tissue and the average gray density were observed with the image analysis system of biomicroscope. Results The enzyme activity of CCO, LDH, SDH, CHE and NOS located in the mouth, muscle fiber, tegumentary membrane, ganglia, liver and pharyngeal cavity of Oncomelania hupensis snails. The enzyme activities of CCO, LDH, SDH, CHE and NOS in the treated group were significantly lower than that in the control group. Conclusions Niclosamide can affect the transmitting of neurohypophysis and obstruct the energy and result in the disorder of the physiological functions in Oncomelania hupensis. It is one of the reasons of Oncomelania hupensis death.
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Objective To develop a novel synergism compound suspension concentrate of niclosamide and chlorphoxim (Co-SCN) and sdudy its characteristics. Methods Niclosamide and chlorphoxim were milled by a ball mill and mixed with different amounts of wetting agent. disper-sant agent, thickener, and water etc. , to develop Co-SCN, and the pH value, thickener, grain size were evaluated. The ultraviolet absorption spectrum of niclosamide and chlorphoxim were measured. The content of niclosamide and chlorphoxim in the solution were assayed by HPLC. Results Co-SCN was a gray thickener fluidity liquid. It was very easy to disperse and could be mixed with water in any proportion. Its pH was 8. 65 and thickener was 137 mpa? s. The grain sizes (diameter) were from 0. 138-19. 953 ?m. Of them more than 95. 6% was smaller than 10 ?m and more than 82. 24% was smaller than 5 ?m. There were three peaks of ultraviolet absorption spectrum for niclosamide: 210, 234 nm and 334 nm respectively. One peak of chlorphoxim was at 269 nm. The novel formulation contained 20.64% niclosamide and 5.26% chlorphoxim. The suspension stability of Co-SCN was 100% for 2 hours and 89. 14% for 4 hours, and otherwise WPN in water was speedy sediment. Conclusion The novel synergism compound suspension concentrate of niclosamide and chlorphoxim is a stable quality and standard formulation.
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0. 05), Conclusion There was the same molluscicidal effect while the active content of SCN was a guarter of active content of WPN by immersion and spraying in the field. SCN is a novel form of niclosamide with high molluscicidal effect and of convenience to use in the field.
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Objective To develop a novel suspension concentrate of niclosamide (SCN) and evaluate its characteristics and molluscicidal effect against Oncomelania snails. Methods Niclosamide was milled by a sand granule mill and mixed with different amounts of wetting agent, dispersant agent, thickener, and water etc., to develop suspension concentrates, and its dispersion, suspensibility and stability were evaluated. According to the results of evaluation the best recipe and quality indexes for producing SCN were selected. The molluscicidal effects against Oncomelania snails were tested under lab condition and in field. Results The novel SCN contained 25% niclosamide (w/w), 1.5%-2.0% wetting agent (RS 3), 4% dispersant (FS 2), 0.10% thickener, a litte of other agent and water. The quality indexes which the SCN reached were as following: the content of niclosamide was more than 25%(w/w); the suspensibal rate was more than 90%; the pH was from 4 to 7; the size of more than 98% granules of niclosamide was smaller than 44?m; the thickener was smaller than 600 mpa.s. The SCN was very stable when it was stored in high or in low temperature. Under lab condition the LC 50 concentrations of SCN by the immersion method for 24, 48 and 72 hours were 0.0474 mg/L, 0.0412 mg/L and 0.0412 mg/L respectively while the LC 50 concentrations of 50% wettable powder of niclosamide (WPN) were 0.0947 mg/L, 0.0583 mg/L and 0.0442 mg/L. In the field death rates of the snails sprayed with 2.0 g/(L?m 2 ) of 25% SCN after 3, 7 and 15 days were 95.77%, 99.07%, 97.09% while the death rates of the snails sprayed with 2.0 g/(L?m 2 )of 50% WPN were 97.37%, 95.17% and 97.41%. Conclusion SCN had stable quality and high molluscicidal effect against Oncomelania snails, and it was suitable to be used in the field. The molluscicidal effect using 2.0 g/(L? m 2 ) of 25% SCN was similar with that using 2.0 g/(L?m 2) of 50% WPN.
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Objective To evaluate the long-term molluscicidal effect of suspension concentrate of niclosamide (SCN) spraying in marshland regions of the Yangtze River. Methods A marshland with Oncomelania snails in Yangzhong City, Jiangsu Province, was selected as the study spot, and a dose of 6-8 g/m2 of SCN was sprayed yearly for four successive years, and the status of snails was investigated. Results From 2004 to 2007, the average densities of living snails were 6.00, 4.25, 2.04, 1.95 snails/0.1 m2, respectively before the use of molluscicide, and 0.86, 0.86, 0.23, 0.16 snails/0.1 m2, respectively after that. The average densities of living snails before and after the use of molluscicide reduced year by year, and the reduction rates of average densities of living snails were 85.67%, 79.76%, 88.49% and 91.78%, respectively from 2004 to 2007. The rate of frames with snails after the use of molluscicide was 73.46% in 2007, with a reduction rate of 86.85% compared with 9.66% of that before the use of molluscicide in 2004, and the average density of living snails reduced from 6.00 snails/0.1 m2 to 0.16 snails/0.1 m2, with a reduction rate of 97.33%. Conclusions After the spraying for four successive years, the density of snails reduces significantly and the molluscicidal effect is stable and reliable. SCN is a formulation of molluscicide for long-term application in marshland regions.
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Objective To observe the molluscicidal effect of 25% suspension concentrate of niclosamide (SCN) against snail eggs and young snails. Methods The experiments with SCN and 50% wettable powder of niclosamide ethanolamide salt (WPN) against the snail eggs and young snails were carried out by the immersion method in laboratory. Results The death rates of snail eggs were both 100% in 0.25 mg/L active content of SCN and in 0.50 mg/L of WPN for 24 hours. The LC_~50(s) of SCN against Oncomelania snail eggs were 0.0506, 0.0496 mg/L and 0.0473 mg/L by immersion for 24, 48 hours and 72 hours respectively, while the LC_~50(s) of WPN were 0.1030, ~0.0962 mg/L and 0.0869 mg/L. The death rates of young snails were both 100% in 0.25 mg/L active content of SCN and WPN for 24 hours. The LC_~50(s) of SCN were 0.0625, 0.0474 mg/L and ~0.0442 mg/L for 24, 48 hours and 72 hours respectively, while the LC_~50(s) of WPN were 0.1088, 0.0825 ~mg/L and 0.0825 mg/L. Conclusion The SCN has high molluscicidal effect against Oncomelania snail in its different developmental stages: egg and young snail.[