Concomitant knockdown resistance allele, L982W + F1534C, in Aedes aegypti has the potential to impose fitness costs without selection pressure

• Published in: Pesticide Biochemistry and Physiology Vol. 193; p. 105422
• Main Authors: Uemura, Nozomi, Furutani, Shogo, Tomita, Takashi, Itokawa, Kentaro, Komagata, Osamu, Kasai, Shinji
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.06.2023; Elsevier BV
• Subjects: Aedes; Aedes - genetics; Aedes aegypti; Allele frequency; Alleles; amino acids; Animals; arboviruses; dengue; Eprobe; Fitness cost; fluorescent dyes; genotyping; heterozygosity; homozygosity; Insecticide Resistance; Insecticide Resistance - genetics; Insecticides; Insecticides - pharmacology; Kdr; Mosquito Vectors; Mosquito Vectors - genetics; mutants; Mutation; pesticide resistance; pesticides; physiology; Pyrethrins; Pyrethrins - pharmacology; selection pressure; sodium channels; viability; Voltage-Gated Sodium Channels; Voltage-Gated Sodium Channels - genetics; yellow fever; Zika Virus; Zika Virus Infection; Zika Virus Infection - genetics; Kdr; Aedes aegypti; Allele frequency; Fitness cost; Eprobe
• DOI: 10.1016/j.pestbp.2023.105422
• ISSN: 0048-3575; 1095-9939

The Aedes aegypti mosquito, is an arbovirus vector that can spread dengue, chikungunya, Zika, and yellow fever. Pyrethroids are widely used to control mosquitoes. The voltage-gated sodium channel (Vgsc) is the target of pyrethroids, and amino acid substitutions in this channel attenuate the effects of pyrethroids. This is known as knockdown resistance (kdr). Recently, we found that Ae. aegypti with concomitant Vgsc mutations L982W + F1534C exhibit extremely high levels of pyrethroid resistance. L982 is located in a highly conserved region of Vgsc in vertebrates and invertebrates. This study aimed to evaluate the viability of Ae. aegypti, with concomitant L982W + F1534C mutations in Vgsc. We crossed a resistant strain (FTWC) with a susceptible strain (SMK) and reared it up to 15 generations. We developed a rapid and convenient genotyping method using a fluorescent probe (Eprobe) to easily and accurately distinguish between three genotypes: wild-type and mutant homozygotes, and heterozygotes. As generations progressed, the proportion of wild-type homozygotes increased, and only 2.9% of mutant homozygotes were present at the 15th generation; the allele frequencies of L982W + F1534C showed a decreasing trend over generations. These observations show that these concomitant mutations have some fitness costs, suggesting that mosquitoes can potentially recover pyrethroid susceptibility over time without pyrethroid selection pressure in the field. [Display omitted] •Eprobe genotyped mosquito genome samples in a short time and at low cost.•The allele frequency of L982W + F1534C gradually decreased over generations.•In the absence of insecticides, there may be fitness costs in the FTWC strains.