| Three aspects of schistosomiasis transmission were the source of infection, route of transmission and susceptible herd, the spread of infectious process involving people, livestock and wild mammals, the only intermediate host snails, as well as many other factors to contaminated water and other natural environmental and social conditions. Whereas the intermediate host snails are having a crucial role both in schistosome transmission dynamics and in schistosomiasis control, its geographic distribution is consistent with schistosomiasis, and therefore control snail is one of the most effective measures for the prevention and control of schistosomiasis transmission, preventing schistosome infection. In China, Prevention and treatment of schistosomiasis practice has proved that the control snail is an effective measure to control schistosomiasis. Currently, the snail control method including molluscicide, physical snail control and biological snail control three categories. physical snail control mainly including cover without soil and sand, hardening conduits, black film mulched, tillage planting, storing water to raise aquatic, digging new trench and filling old ditch,ect.the effect is better and will not pollute the environment.However, due to the large amount of engineering and higher investment, it is only suitable for use in some key areas. Biomolluscicides mainly including biological competition snail control, preyed snail control, killing snail of microorganism, Biological snail control have the advantages of no pollution, small investment, etc, but no actual field application,confined to the theory stage of snail control research. Molluscicide including chemical-based and plant molluscicide, plant molluscicide has the advantages of good snail control effect and small pollution, However, due to its snail control active ingredient is not entirely clear, extraction process complexity and high cost,etc. Mostly snail control effect is better confined to the laboratory, no wide range application of field.At present mainly snail control method is given priority to chemical-based molluscicide. there are wide variety of chemical molluscicide,which has several advantages such as have high effects, low consumption, the stable effect,etc.Niclosamide was the only recommended molluscacide by WHO,which has well snail control effect.However, there are disadvantages of low solubility,maximum toxic effect to fish, clams and other aquatic organisms. And long-term single application of niclosamide kill snails may lead to niclosamide tolerance, reduceing the snail control effect.Through technology of molluscicide compound, which could improve the snails sensitivit and the effect of snail control when decrease the dosage of drugs, to some extent, can also overcome the shortcoming of different drugs, complementing each other with their own advantages, so as to provide the evidence for the safe, efficient, economic and environmental protection molluscicide application in the field.Suspension concentrate of 26% metaldehyde and niclosamide composed by 25% niclosamide and 1% of metaldehyde. the dosage form has advantages of its small particle size, large active surface area, sharp penetration, low cost and high efficacy,etc.This research carried on the experiment of MNSC against Oncomelania snails were performed by immersion and spray methods in laboratory and field, and the wettable powder of 50% niclosamide ethanolamine salt (WPN) and flesh water were set as the controls, in according to operation requirements introduce by "Pesticide registration molluscicided agent efficacy test methods and evaluation (NY/T 1617-2008) "Adopting evaluation indicators of pesticide registration molluscicided agent efficacy results of laboratory and field tests by immersion and spray, In laboratory,by immersion method,LC50 values of MNSC at 24 h、48 h and 72 h were 0.29 mg/L、0.26 mg/L and 0.22 mg/L respectively; by the immersion method for 1 d,the snail death rates were 100.00% when the concentration of MNSC were equal or greater than 2.00 mg/L as well as the 2 mg/L WPN.In laboratory, by the spray method, the snail death rates were higher than 96.00% on the 1st.3rd and 7th day when the dosage of MNSC was higher than 2.00 g/m2 as well as the 2mg/L WPN. At the field by the immersion method for 1d,the snail death rates were 98.89% when MNSC with concentration of 2.00g/m3, as well as the 2mg/L WPN.In the field,by the spray method, the snail death rates were higher than 91.67% on the 1st、3rd and 7th day when the dosage of MNSC was higher than 2.00g/m2 as well as the 2g/m2 WPN.The molluscicidal effect of MNSC is as the same as WPN by immersion 2.00 mg/L and spray methods 2.00 g/m2 in laboratory and field, MNSC has a good molluscicidal effect on Oncomelania hupensis. And at the same dose, while keeping up with snail control effect,MNSC actual Niclosamide content is only half of the WPN,which reduce the actual usage of molluscicide and residues in the environment, thereby reducing the adverse effects of drugs on the environment, and its price is lower than the Niclosamide, which worth continue to expand the application in the field. |
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