Tick infestations and tick-borne diseases are among the leading causes of economic losses in the cattle industry worldwide. Amitraz is one of the most commonly used chemical acaricides against the cattle tick Rhipicephalus (Boophilus) microplus. Resistance to amitraz has been reported in many countries but not in the Philippines. This study aimed to determine whether cattle ticks from provinces in northern and southern Luzon, Philippines, are resistant to amitraz. Engorged or nearly engorged female ticks were collected from 21 farms and allowed to lay eggs to produce larvae. Larval packet test (LPT) was performed using three concentrations of amitraz, as well as a negative control (diluent). Reverse-transcription polymerase chain reaction (RT-PCR) was also performed to amplify a fragment of the octopamine/tyramine receptor gene and was subjected to sequence analysis by multiple nucleotide and amino acid sequence alignments together with reference strain, amitraz-susceptible strain, and amitraz-resistant strain reported in other countries. LPT results suggest the absence of resistance in all of the tested populations. Interestingly, analysis of the octopamine/tyramine receptor amino acid sequence revealed four out of 14 larval pools having substitutions similar to that of the reported amitraz-resistant strains. Although no apparent resistance was observed in this study, prudent use of amitraz should be practiced as the development of resistance is still likely to occur in the future.

ick虫感染和tick传播疾病是全球养牛业经济损失的主要原因。Amitraz是针对牛tick Rhipicephalus（Boophilus）microplus的最常用化学杀螨剂之一。据报道，许多国家对阿米特拉斯有抗药性，但菲律宾却没有。这项研究旨在确定菲律宾吕宋岛北部和南部各省的牛tick是否对双甲raz具有抗性。从21个农场中收集了饱食或接近饱食的雌tick，并允许其产卵以生产幼虫。使用三种浓度的阿米特拉斯和阴性对照（稀释剂）进行幼虫包试验（LPT）。还进行了逆转录聚合酶链反应（RT-PCR）来扩增章鱼胺/酪胺受体基因的片段，并通过多核苷酸和氨基酸序列比对以及参考菌株，对阿米特拉的敏感菌株和在其他国家/地区也报道了抗甲酰胺类菌株。LPT结果表明在所有测试人群中均没有耐药性。有趣的是，对章鱼胺/酪胺受体氨基酸序列的分析显示，在14个幼虫库中有4个具有与已报道的抗阿米特拉斯的菌株相似的取代。尽管在这项研究中未观察到明显的耐药性，但由于未来仍可能发生耐药性，因此应谨慎使用阿米特拉。