灌渠内药物灭螺对钉螺及感染性钉螺的影响

Impact of snail control with niclosamide on population of snails and infected sn ails in main channel in man-made irrigation area

目的 了解在人工灌溉水渠干渠内 ,常规药物灭螺对钉螺及感染性钉螺消长的影响。方法 在安徽钓鱼台水库灌区 ,根据当地灭螺规划 ,在其计划灭螺区干渠内选择螺情观察点 ,同时选非计划灭螺支渠为对照 ;2 0 0 2年12月～ 2 0 0 3年 11月份 ,每月沿渠两边系统抽样查螺 ,室内压碎鉴定死活 ,并观察感染血吸虫情况。常规药物灭螺的时间、方法、药量及实施均由当地业务部门确定完成。结果 灭螺前钉螺死亡率在干渠和支渠变化趋势基本一致 ;4月 2 0日干渠灭螺 ,灭螺后 10 ,37d时干渠钉螺死亡率分别为 2 4 4 6 %及 4 3 0 1% ,但 8月底为 1 2 5 % ,同期未灭螺的支渠钉螺死亡率变化不大 ;灭螺前干渠有 3个月、支渠有 1个月检出感染性钉螺 ,灭螺后 4～ 6月份在干渠仅于灭螺后 10d发现感染性钉螺 ,未灭螺支渠 5月份检出感染性钉螺 ;8月 31日以后钉螺感染率及感染性钉螺密度在干、支渠均上升。结论 在人工灌区的引水干渠内 ,常规药物灭螺在预防人群感染方面可能起一定作用 ,但对年度钉螺及感染性钉螺螺口消长的作用有限。

Objective To learn the impact of the routine snail control with niclosamide on the population of snails and infected snails in the main cha nnel in the man-made irrigation area.Methods In the irrigation area of Diaoyutai reservoir in Anhui,a section of the main channel,which the mullicicide measure was imple mented according to the local plan,was selected as a trial spot.A neighbori ng branch without no snail was selected as a control spot.Systemic survey of sn ails was carried out from the Dec of 2002 to the Nov of 2003.All snails were a natomized.The date,method,dosage of Nicl osamide and conduction were deicded and completed by the local station of anti-S chistosomiasis.Results Before the snail control,the trend of the death r ate in the main channel was generally the same as that in the branch.Af ter mullicicide measure was given to the channel on the 20th of Apr,th e death rate in the channel on the 10th day and the 37th day was respectively 24.46% and 43.01%,but it was 1.25% at the end of Aug.Mean while the death rate in the branch didn't change grealty.During the period ahe ad of the 20th of Apr,there were 3 months in the channel and 1 month i n the branch when infected snails were found.During the period from Apr to Jun ,infected snails were discovered both in the channel on the 10th day af t er snail control and in the branch in May.The infection rate of snails and infec ted snail density in the two spots rose up during the rest time of the year.Conclusion In the main channel of the man-made irrigation area,snail control with Niclosamide,as an ordinary measure,might play an import ant role in preventing human from infection with Schistosoma,but the role in red ucing the population of snails and infected snails in near future was very limit ed.