Abstract:

Objective To understand the sensitivity of Oncomelania snails collected from different months to niclosamide，so as to provide the scientific evidence for the standardization of methods for molluscicide screening and efficacy evaluation in labora? tory. Methods The snails collected from the marshland of Zhenjiang City，Jiangsu Province month by month from June 2010 to May 2011. After being raised in laboratory for 24 h，the snails were randomly grouped，and then immersed in different concentra? tions of 50% wettable powder formulation of niclosamide ethanolamine salt at (25±1) ℃ with a humidity of 60%. The dead snails were identified and counted，and the mortality rate of snails and median lethal concentration (LC50) were calculated. Results When the snails were immersed in the solutions of niclosamide at concentrations of more than 0.5 mg/L for 24 h，all the snails col? lected from different months were dead，while 60%-100% of the snail mortality was achieved for 0.250 mg/L niclosamide， 3%-27% for 0.125 mg/L niclosamide，and 3%-20% for 0.062 5 mg/L niclosamide. When the concentration was lower than 0.032 mg/L，the niclosamide was not toxic to the snails within 24 h. The LC50 value was 0.140-0.209 mg/L for 24 h. When the snails were immersed in the solutions of niclosamide at concentrations of more than 0.5 mg/L for 48 h，all the snails collected from different months were dead，while 90%-100% of the snail mortality was achieved for 0.250 mg/L niclosamide，3%-57% for 0.125 mg/L ni? closamide，3%-13% for 0.062 5 mg/L niclosamide，and 0-10% for 0.032 mg/L niclosamide. When the concentration was lower than 0.016 mg/L，the niclosamide was not toxic to the snails within 48 h. The LC50 value was 0.112-0.170 mg/L for 48 h. There were no significant differences in the mortality of snails caused by niclosamide treatment observed at 24 and 48 h (P values = 0.374 and 0.267，respectively). Conclusions There are little changes in the sensitivity of snails collected from different months to ni? closamide，with minor fluctuations in LC50 values. Such a finding indicates that the snails collected from different months have few effects on screening of molluscicides and efficacy evaluation.

Key words: Oncomelania snail；50% wettable powder formulation of niclosamide ethanolamine salt (WPN)；Molluscicidal ef? fect； Median lethal concentration (LC50)

摘要：

目的 目的 了解不同月份钉螺对氯硝柳胺乙醇胺盐可湿性粉剂 （WPN） 的敏感性， 为制定杀螺药筛选与药效评价标准化方法提供参考依据。方法 方法 自2010年6月至2011年5月每月采集江苏省镇江市江滩钉螺， 实验室饲养24 h后随机分组， 用现配制的WPN药液在温度 (25±1) ℃、 湿度60%、 光照充足的培养箱内对上述钉螺进行浸杀试验， 采用敲击法鉴别钉螺死活并计数， 计算钉螺死亡率及其半数致死浓度 （LC50 ）。结果 结果 0.5 mg/L及以上浓度WPN浸杀钉螺24 h， 各月采集的钉螺死亡率均为100%； 浓度为0.25 mg/L时， 钉螺死亡率为60%~100%； 浓度为0.125 mg/L时， 钉螺死亡率为3%~27%； 浓度为 0.062 5 mg/L时， 钉螺死亡率为3%~20%；0.032 mg/L及以下浓度钉螺死亡率均为0； 浸杀24 h钉螺LC50为0.140~0.209 mg/L。 0.5 mg/L及以上浓度WPN浸杀钉螺48 h， 各月采集的钉螺死亡率均为100%； 浓度为0.25 mg/L时， 钉螺死亡率为90%~ 100%； 浓度为0.125 mg/L时， 钉螺死亡率为3%~57%； 浓度为0.062 5 mg/L时， 钉螺死亡率为3% ~13%； 浓度为0.032 mg/L 时， 钉螺死亡率为0~10%； 0.016 mg/L及以下浓度时， 钉螺死亡率均为0； 浸杀48 h钉螺LC50为0.112~0.170 mg/L。不同月份钉螺经WPN浸杀24 h与48 h时的死亡率差异均无统计学意义 （P 均 > 0.05）。结论 结论 全年不同月份采集的钉螺对WPN的 LC50波动范围不大， 敏感性变化较小， 对杀螺药筛选以及药效评价结果影响有限， 在实验误差范围内。

关键词: 湖北钉螺； 50％氯硝柳胺乙醇胺盐可湿性粉剂 （WPN）； 杀螺效果； 半数致死浓度(LC50)