Observation on frequency and effect of dusting molluscicide in irrigation canals / 中国血吸虫病防治杂志

Objective To study a new method and technical specification for Oncomelania snail control in irrigation canals.Methods Four percent niclosamide ethanolamine salt dustable powder was dusted in a test canal three times continuously,and a control canal was set up at the same time.The molluscicidal frequency and effect of niclosamide ethanolamine salt powder was observed and the results,including the change of living snail frames,average density of living snails and mortality of snails,were analyzed.Results Between the third and fifteenth day after the first dusting in the test canal,the reduction rate of the density of snails was more than 90% and after the second and third dusting,the reduction rate was more than 99%.For the average rates of living snail frames and mortality of snails,there were significant differences between the first dusting and later two dustings,while there was no significant difference between the second dusting and the third dusting.On the thirtieth and ninetieth day after the third dusting,the effect of snail control was still satisfactory.There were significant differences between the test canal and control canal about all the observation indexes.Conclusion The application of 4% niclosamide ethanolamine salt dustable powder is efficient in the snail control in irrigation canals,and the suitable frequency of dusting is 2 or 3 times.

Cost-benefit analysis of project with mode of collecting water from middle layer of water body by culvert pipelinet / 中国血吸虫病防治杂志

Objective To evaluate the cost-benefit of the project with the mode of collecting water from middle layer of water body by the culvert pipelinet.Methods The cost-benefit analysis was carried out by the way of benefit-cost ratio for the project with the mode of collecting water from middle layer of water body by the culvert pipelinet without indirect cost and indirect benefit,and according to the price of 2005.Results The direct costs was 34 thousand yuans in the project with the mode of collecting water from middle layer of water body by the culvert pipelinet.The saved costs of prevention and treatment were 1011 thousand yuans,the net benefit was 977 thousand yuans and the net benefit-cost ratio was 28.7∶1 following the project implemented.Conclusion The investment is small but the benefit is high in the project of collecting water from middle layer of water body by the culvert pipelinet.The technique has the notable worthiness of applications.

Efficiency of prevention of Oncomelania snail dispersal with the mode of leading water from middle level of water body by the culvert pipelinet / 中国血吸虫病防治杂志

Objective To evaluate the efficiency of prevention of Oncomelania snail dispersal with the mode of leading water from middle level of water body by the culvert pipelinet in the electric pumping station. Methods The snails were detected in the floats by riverhead and the irrigation areas, and the snails were hold up by the block in the exit of pump. The snail investigation was carried out in the irrigation system areas and the results were compared between the study area and the control area. Results The snails were discovered in the floats of riverhead of the electric pumping station. However, there were no any snails in the exit of pump after the block snail treatment and no any snails in the irrigation areas, either. There were snails in the control areas Conclusion The mode of leading water from middle level of water body by the culvert pipelinet is very effective for the prevention of Oncomelania snail dispersal.