Department of Veterinary Parasitology, College of Veterinary Science, Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana, 141004, India.
Department of Veterinary Parasitology, College of Veterinary Science, Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana, 141004, India.
Ticks Tick Borne Dis. 2021 Jan;12(1):101578. doi: 10.1016/j.ttbdis.2020.101578. Epub 2020 Oct 5.
Acaricide resistance is one of the greatest threats to sustainable and effective control of vector ticks worldwide. The amitraz resistance status in cattle tick, Rhipicephalus microplus populations collected from 18 districts of Punjab in north-western India were characterized using bioassay and molecular assays. The modified larval packet test was used and the resistance factors (RF) against amitraz for the field populations were in the range of 0.36-4.85, indicating level I resistance status in ten populations. Characterization of a partial segment of the octopamine/tyramine (OCT/Tyr) receptor gene of R. microplus field populations from Punjab revealed a total of 18 nucleotide substitutions in the coding region out of which 5 were non-synonymous substitutions. Three of these non-synonymous substitutions (T8P, V15I and A20 T) were earlier reported in American and South African populations of R. microplus. Among the two single nucleotide polymorphisms (A22C-T8P; T65C-L22S) potentially linked to amitraz resistance in American, South African and Zimbabwean resistant populations, only the T8P substitution was recorded from the Barnala population. The PCR-RFLP assay using EciI restriction enzyme was used for genotyping of the larvae as homozygous resistant (RR), homozygous susceptible (SS) and heterozygous (SR). Genotyping of 514 larval DNA samples from 18 field populations revealed 92.8 % larval population as SR and the remaining 7.2 % as RR genotypes. The percentage of resistant alleles in the tick populations was 53.6 (range 50.0-57.2) indicating its moderate distribution in the region. The present study is the pioneer report establishing the hypothesis that amitraz-resistance is recessively inherited and heterozygous individuals show phenotypic susceptibility to the drug in the Indian tick populations.
杀蜱剂耐药性是全球可持续有效控制病媒蜱的最大威胁之一。本研究采用生物测定和分子检测方法，对从印度西北部旁遮普邦 18 个地区采集的牛蜱（Rhipicephalus microplus）种群的抗螨灵抗性状况进行了研究。改良的幼虫包被试验（modified larval packet test）表明，田间种群对杀螨灵的抗性因子（RF）在 0.36-4.85 之间，表明其中 10 个种群处于 I 级抗性水平。对旁遮普邦田间种群的部分章鱼胺/酪胺（octopamine/tyramine，OCT/Tyr）受体基因片段的特征分析显示，编码区共发生 18 个核苷酸取代，其中 5 个是非同义取代。这 5 个非同义取代中有 3 个（T8P、V15I 和 A20 T）之前在美洲和南非的 R. microplus 种群中报道过。在与美洲、南非和津巴布韦的抗药性种群中与杀螨灵抗药性相关的两个单核苷酸多态性（A22C-T8P；T65C-L22S）中，只有 Barnala 种群记录到 T8P 取代。采用 EciI 限制性内切酶的 PCR-RFLP 分析对幼虫进行基因型分型，分为纯合抗性（RR）、纯合敏感（SS）和杂合（SR）。对来自 18 个田间种群的 514 个幼虫 DNA 样本进行基因分型，结果显示 92.8%的幼虫种群为 SR，其余 7.2%为 RR 基因型。在蜱种群中，抗性等位基因的百分比为 53.6（范围为 50.0-57.2），表明其在该地区的中等分布。本研究首次提出了假设，即抗螨灵抗性是隐性遗传的，杂合个体对药物表现出表型敏感性。
