Jonsson N N, Hope M
School of Veterinary Science, University of Queensland, Qld 4072, Australia.
Vet Parasitol. 2007 May 31;146(3-4):193-8. doi: 10.1016/j.vetpar.2007.03.006. Epub 2007 Apr 19.
Amitraz is a rapidly acting acaricide that has been in use for the control of cattle ticks for more than 30 years. Resistance against amitraz was first reported in Boophilus microplus in Australia in 1980 but has been slow to spread in comparison to resistance against synthetic pyrethroids. The most recent estimate of prevalence of amitraz resistance in Australia is 10.8%. In Mexico, the development and distribution of amitraz appears to have been more rapid and the prevalence has been estimated to be 19.4% in Yucatan state. In New Caledonia, about 10% of properties were confirmed to have amitraz resistance. There is little reliable information on the prevalence of amitraz resistance in southern Africa. Risk factors have been identified, but the small sample sizes in the studies that have attempted to identify risk factors using survey data suggest caution in their interpretation. Regional variation in prevalence has been reported, as has a positive relationship with frequency of acaricide application. There is evidence to suggest that in Australia, amitraz resistance might have emerged on a small number of properties and been disseminated by cattle movements. There is also some evidence to suggest that amitraz resistance can diminish in the field when selection pressure is not applied. The mode of inheritance of amitraz resistance is uncertain and it has been suggested that it is a polygenic trait. The mechanism of amitraz resistance is unknown. Two possibilities have been proposed: octopamine receptor and monoamine oxidase. There is some equivocal support for both possibilities. The larval packet test bioassay is the most reliable method of diagnosing amitraz resistance in B. microplus, and this test has been modified by Miller to provide more accuracy and repeatability. Molecular tests are in development but will not eliminate the need for the bioassay.
双甲脒是一种速效杀螨剂，已用于控制牛蜱超过30年。1980年在澳大利亚首次报道微小牛蜱对双甲脒产生抗性，但与对合成拟除虫菊酯的抗性相比，其传播速度较慢。澳大利亚最近对双甲脒抗性流行率的估计为10.8%。在墨西哥，双甲脒的发展和分布似乎更快，据估计尤卡坦州的流行率为19.4%。在新喀里多尼亚，约10%的养殖场被证实存在双甲脒抗性。关于南部非洲双甲脒抗性流行率的可靠信息很少。已确定了风险因素，但试图利用调查数据确定风险因素的研究样本量较小，这表明在解释这些因素时需谨慎。已报道了流行率的区域差异，以及与杀螨剂施用频率的正相关关系。有证据表明，在澳大利亚，双甲脒抗性可能在少数养殖场出现，并通过牛的移动传播。也有一些证据表明，当不施加选择压力时，双甲脒抗性在田间可能会减弱。双甲脒抗性的遗传模式尚不确定，有人认为它是一种多基因性状。双甲脒抗性的机制尚不清楚。提出了两种可能性：章鱼胺受体和单胺氧化酶。对这两种可能性都有一些模棱两可的支持。幼虫包囊试验生物测定法是诊断微小牛蜱对双甲脒抗性最可靠的方法，米勒对该试验进行了改进，以提高准确性和可重复性。分子检测正在开发中，但不会消除对生物测定法的需求。
