School of Applied Animal Production and Biotechnology, College of Veterinary and Animal Sciences, Mannuthy, Thrissur, Kerala, 680651, India.
Department of Veterinary Parasitology, College of Veterinary and Animal Sciences, Mannuthy, Thrissur, Kerala, 680651, India.
Exp Appl Acarol. 2021 Jun;84(2):485-496. doi: 10.1007/s10493-021-00627-1. Epub 2021 May 28.
Brown dog tick, Rhipicephalus sanguineus sensu lato, an important ectoparasite transmitting several pathogens, is the most common tick species infesting dogs. Control of ticks being central to the control of fatal tick-borne diseases, this study attempted to assess the susceptibility/resistance of brown dog ticks to synthetic pyrethroids, the commonly used acaricides against ticks. Larval packet assay revealed 60% of isolates tested to be resistant and tolerant to deltamethrin as per the resistance factor that ranged from 1 to 53.7. Sequence analysis of the PCR amplified product of domain II S4-5 linker of sodium channel gene in R. sanguineus revealed novel polymorphisms, viz., C190A, G215T and T270C. In domain III S6 region of the gene, a T2134C mutation was observed. Genotyping with allele-specific PCR targeting domain II S4-5 linker region using single larvae revealed that most R. sanguineus larvae in the study population were homozygous resistant (RR) genotypes, followed by heterozygous (RS) and homozygous susceptible (SS) genotypes. A higher proportion of RS genotypes was also observed in domain III S6 region. This first report of genotyping of Indian R. sanguineus to analyse synthetic pyrethroid resistance highlights the need to devise alternate control strategies to reduce the brown dog tick population.
褐犬蜱，即广义的 Rhipicephalus sanguineus sensu lato，是一种重要的外寄生虫，可传播多种病原体，是寄生在犬类身上最常见的蜱种。控制蜱虫是控制致命蜱传疾病的核心，本研究试图评估褐犬蜱对合成拟除虫菊酯的敏感性/抗性，这是一种常用于蜱虫防治的杀螨剂。幼虫包被法检测结果显示，在所测试的 60%分离株中，对溴氰菊酯的抗性和耐受力符合抗性因子范围（1 至 53.7），表明这些分离株具有抗性。褐犬蜱钠离子通道基因 II 区 S4-5 连接区 PCR 扩增产物的序列分析显示了新的多态性，即 C190A、G215T 和 T270C。在该基因的 III 区 S6 区域观察到 T2134C 突变。使用针对 II 区 S4-5 连接区的等位基因特异性 PCR 对单个幼虫进行基因分型显示，研究人群中的大多数褐犬蜱幼虫均为纯合抗性（RR）基因型，其次是杂合（RS）和纯合敏感（SS）基因型。在 III 区 S6 区域也观察到了更高比例的 RS 基因型。这是首次对印度褐犬蜱进行基因分型以分析合成拟除虫菊酯抗性的报道，突出表明需要制定替代控制策略来降低褐犬蜱的种群数量。
