Abstract: Objective To evaluate the molluscicidal effect of niclosamidate against Oncomelania hupensis in laboratory and explore its mechanism by determining the enzyme activities of six important enzymes in snail soft tissues. Methods O. hupensis snails were treated with niclosamidate at the concentration of 1.25 mg/L for 24 h and the snail soft tissues were separated and prepared for analysis. The enzyme activities of NOS， AChE， SDH， LDH， ACP and AKP were determined by ultraviolet spectrophotometry. The morphology of the snail soft tissue was also observed. Results Niclosamidate exhibited a potent molluscicidal effect against O. hupensis at the concentration of 5.00 mg/L with a mortality of 96.67% by the immersion method in laboratory. After immersed with niclosamidate （1.25 mg/L） for 24 h， the enzyme activities of NOS， AChE， ACP and AKP were significantly decreased compared with those of the controls （all P < 0.01）. There were no significant changes observed in the enzyme activities of SDH and LDH （both P > 0.05）. Conclusion Niclosamidate possesses a potent molluscicidal effect against O. hupensis and its molluscicidal mechanism is probably by affecting the transmission of neurotransmitters， interfering with the circulation， metabolism and motor functions that require NO， and hindering the digestion and absorption of nutriments， which eventually result in the death of the snails.

Key words: Niclosamidate； Oncomelania hupensis； Molluscicidal effect； Enzyme activity

摘要： 目的 实验室评价灭螺酯的杀螺效果，并观察经灭螺酯处理的钉螺酶活性的变化，探讨灭螺酯杀螺机制。方法 采用实验室浸杀法，浸泡 24、48、72 h后取活螺用考马斯亮蓝法进行蛋白含量测定及紫外分光光度法作酶活性检测。结果 灭螺酯在5.00 mg/ L浓度下浸杀钉螺效果明显，死亡率达96.67%。经1.25 mg/L灭螺酯浸泡24 h的钉螺软组织的NOS、AChE、ACP和AKP的酶活性较溶剂对照组均有显著降低，差异具统计学意义（P均＜0.01）；而SDH和LDH的酶活性相较溶剂对照组无显著性变化（[P 均> 0.05]）。结论 灭螺酯对钉螺的杀灭作用很可能是通过影响钉螺的神经介质传导、扰乱需NO参与的循环、代谢和运动功能、并阻碍其消化、吸收、运输营养物质，从而使钉螺多项生理生化功能紊乱，最终导致钉螺死亡。

关键词: 灭螺酯；湖北钉螺；杀螺效果；酶活性