Department of Parasitology, College of Veterinary and Animal Sciences, G.B. Pant University of Agriculture and Technology, Pantnagar 263145, Uttarakhand, India.
Exp Appl Acarol. 2012 Nov;58(3):315-25. doi: 10.1007/s10493-012-9584-3. Epub 2012 Jun 5.
Rhipicephalus (Boophilus) microplus is an economically important ectoparasite of cattle. Chemical acaricides remain the most practical method for control of these pests. During past two decades there have been increasing reports of resistance development against synthetic pyrethroids in tick populations of this species throughout the world. A study was conducted to determine the level of susceptibility of R. (B.) microplus to deltamethrin collected from different geographical locations of northern India. LPT bioassay results revealed LC(50) values of deltamethrin ranging from 0.035 to 0.00037 % A.I. Esterase profile of the tick larval extracts using native PAGE, revealed 5 bands of esterase activity designated EST-5 to EST-1A. Inhibitory tests recognized EST-1, EST-2 and EST-3 as Acetylcholinesterases (AchEs), EST-4 and EST-5 as Carboxylesterases (CaEs). The band intensity varied between tick populations of various locations, being more intense in case of the resistant populations. An extra band of esterase activity (EST-1A) was obtained in larval extracts of ticks from 3 locations. This increased esterase activity may be involved in the resistance development in these tick populations. Acaricide resistance is a multi-factorial phenomenon, thus other causes of increased resistance like sodium channel mutation and reduced drug penetration (e.g. cuticle thickening) and behavioural changes (e.g. avoiding the pesticides) are to be tested in future in order to confirm the basic cause of the resistance development in these acaricide resistant tick populations.
微小牛蜱是一种重要的经济上的牛体外寄生虫。化学杀蜱剂仍然是控制这些害虫的最实用的方法。在过去的二十年中，世界各地该物种的蜱种群对合成拟除虫菊酯的抗药性发展报告越来越多。本研究旨在确定从印度北部不同地理位置采集的微小牛蜱对溴氰菊酯的敏感性水平。LPT 生物测定结果显示溴氰菊酯的 LC（50）值范围为 0.035 至 0.00037%有效成分。使用天然 PAGE 对蜱幼虫提取物的酯酶图谱进行分析，显示出 5 条酯酶活性带，命名为 EST-5 至 EST-1A。抑制试验将 EST-1、EST-2 和 EST-3 识别为乙酰胆碱酯酶（AchE），EST-4 和 EST-5 为羧酸酯酶（CaE）。不同地理位置的蜱种群之间的带强度不同，抗性种群的带强度更高。在来自 3 个地点的蜱幼虫提取物中获得了一条额外的酯酶活性带（EST-1A）。这种增加的酯酶活性可能与这些蜱种群的抗药性发展有关。杀蜱剂抗性是一种多因素现象，因此，其他增加抗性的原因，如钠离子通道突变和药物渗透减少（例如，角质层增厚）和行为变化（例如，避免使用杀虫剂），在未来需要进行测试，以确认这些杀蜱剂抗性蜱种群抗药性发展的基本原因。
