1.A.9.5.10
GABA gated chloride channel of 537 aas and 4 TMSs, GABA or Rdl.  The tropical cattle tick, Rhipicephalus microplus, is one of the most damaging parasites that affects cattle in tropical and subtropical regions in the world. Tick resistance to acaricides is dispersed worldwide, and a number of associated mutations in target site genes have been described. Phenylpyrazole (e.g., fipronil) and cyclodiene (e.g., lindane, dieldrin) insecticides both have the same mode of action, blocking the GABA-gated chloride channel encoded by the GABA-Cl gene. A conserved mutation, rdl (resistance to dieldrin) is found across a number of arthropods resistant to cyclodienes and phenylpyrazoles. In ticks, the mutation T290L, was identified in the second transmembrane (TMS2) domain of the GABA-gated chloride channel of Australian cattle tick populations that are resistant to dieldrin, but other mutations giving rise to resistance have been described. Cross-resistance between fipronil and lindane was reported in R. microplus populations (Castro Janer et al. 2019).