C190A knockdown mutation in sodium channel domain II of pyrethroid-resistant Rhipicephalus appendiculatus.

This study investigated the target site mutations in the partial sequence of voltage-sensitive sodium channel (VSSC) domain II of synthetic pyrethroid (SP)-resistant Rhipicephalus appendiculatus. Genomic DNA was extracted from seven tick populations (two susceptible and five resistant) collected from central, eastern and southwestern Uganda. The PCR amplicons of the VSSC domain II were cloned and sequenced to determine novel single nucleotide polymorphisms (SNP). A non-synonymous mutation C78 A corresponding to C190 A was found in all the five SP-resistant ticks. The C78 A mutation led to amino acid substitution from leucine to isoleucine (L21I) which was previously reported to confer knockdown (kdr) mutation in R. (Boophilus) microplus. The genetic confirmation of SP-resistant R. appendiculatus in central and southwestern Uganda calls for an urgent strategy for controlling the ticks.