Glutamate-gated chloride channel gene polymorphisms and transcriptome analysis of detoxification genes associated with ivermectin resistance in Rhipicephalus (Boophilus) microplus

Our study aims to identify genetic changes in the glutamate-gated chloride (GluCl) channel genes of ivermectin-resistant Rhipicephalus (Boophilus) microplus, which are a significant pest for livestock and can transmit Babesia pathogens. Ivermectin is a macrocyclic lactone acaricide that acts on the GluCl channel and is used to control internal parasites and ticks in Latin America. Ivermectin-resistant R. microplus populations have been reported from this region, and there is evidence that metabolic detoxification and target site insensitivity are associated with this resistance. Our major goal is to identify single nucleotide polymorphisms (SNPs) in these GluCl genes from ivermectin-resistant R. (B.) microplus strains and to evaluate whether they may confer target-site insensitivity.



RNA extracted from individual adult female ticks, both susceptible and resistant as determined by a larval immersion test, were used for cDNA synthesis. The segment containing the putative sequences of R. microplus GluCl genes was amplified, and the PCR products sequenced to detect SNPs within the GluCl genes. We aim to develop a real-time PCR high-resolution melting analysis assay for efficient genotyping of different ivermectin resistance-related polymorphisms. In preliminary research, we identified 19 SNPs within a laboratory-maintained susceptible strain compared with a previously published GluCl gene sequences, and we detected putative alternative splicing in the 5’ end of the R. microplus GluCl gene.



We will use transcriptome analysis to evaluate whether gene families involved in metabolic detoxification are associated with ivermectin resistance by comparing their expression levels between ivermectin-resistant and -susceptible R. (B.) microplus strains.