Widespread occurrence of copy number variants and fixation of pyrethroid target site resistance in () from southern Côte d'Ivoire.

Resistance to pyrethroid and organophosphate insecticides in the malaria vector () is conferred by a variety of genetic mutations, including single nucleotide polymorphisms (SNPs) and copy number variants (CNVs). Knowledge of the distribution of these mutations in mosquito populations is a prerequisite for establishing better strategies for their management. In this study, a total of 755 () from southern Côte d'Ivoire were exposed to deltamethrin or pirimiphos-methyl insecticides and were screened to assess the distribution of SNPs and CNVs known or believed to confer resistance to one or other of the insecticide classes. Most individuals from the () complex were identified by molecular tests as . Survival to deltamethrin (from 94% to 97%) was higher than to pirimiphos-methyl (from 10% to 49%). In (), the SNP in the Voltage Gated Sodium Channel () at the 995F locus (-995F) was fixed, while other target site mutations were rare or absent (402L: 0%; 1570Y: 0%, Acetylcholinesterase -280S: 14%). In , -995F was the target site SNP found at highest frequency (65%) followed by other target site mutations (402L: 36%; 1570Y: 0.33%; -280S: 45%). The -995S SNP was not present. The presence of the -280S SNP was found to be significantly linked to the presence of the -, _AgDup. Significant association was found between the presence of the _AgDup and pirimiphos-methyl resistance in () but not in . The deletion _Del97 was found in one specimen of (). Four CNVs in the gene cluster, which contains genes of known importance for resistance, were detected in , the most frequent being Dup 7 (42%) and Dup 14 (26%). While none of these individual CNV alleles were significantly associated with resistance, copy number in the gene region in general was associated with increased resistance to deltamethrin. Elevated expression of was nearly associated with deltamethrin resistance, although there was no association of resistance with copy number. Use of alternative insecticides and control methods to arrest resistance spread in populations is merited.