Insecticide resistance status and high frequency of kdr mutations in Aedes aegypti in Tegucigalpa, Honduras

Background: Aedes aegypti is the primary vector of arboviruses including dengue, Zika, and chikungunya. The primary approach to control vector populations and reduce the transmission of these arboviruses during outbreaks is the use of insecticide spraying. However, the prolonged use of insecticides promotes resistance due to the selective pressure exerted on mosquito populations. This study aimed to conduct a phenotypic assessment of insecticide resistance and characterize the main knockdown resistance ( kdr ) mutations in Ae. aegypti populations collected in the Central District of Honduras. Methods: Larvae of Ae. aegypti were collected from four localities in the Central District of Honduras between May and June of 2023. Bioassays to determine susceptibility to deltamethrin, permethrin, malathion, and bendiocarb were carried out. For each location and phenotype, F1534C and V1016I kdr allele frequencies and haplotypes were calculated. Sequencing analyses were employed to genotype additional positions of interest on the vgsc gene. Results: A total of 1,592 Ae. aegypti females were phenotyped in the bioassays. Only two populations were resistant to deltamethrin. Conversely, all populations were resistant to permethrin and malathion, and all populations were susceptible to bendiocarb. The genotyping of 275 individuals revealed the presence of mutant alleles at both kdr loci (1016I and 1534C). The overall allele frequencies for 1534C and 1016I were 1.0 and 0.89, respectively. Variability of frequencies for 1016I was observed between localities, with two populations exhibiting a frequency of 1.0 for the mutant allele, while the rest ranged from 0.48 to 0.97. No additional mutations were detected on the vgsc gene. Conclusion: This study provides evidence regarding the resistance status of Ae. aegypti to insecticides used for vector control in Honduras. Additionally, the high frequency of permethrin resistance and of kdr mutations suggests that the mosquito populations have been under selective pressure from pyrethroids. This information could be integrated into vector control policies in Honduras to develop more targeted and effective strategies for combating mosquito-borne diseases.