The 1014F knockdown resistance mutation is not a strong correlate of phenotypic resistance to pyrethroids in Florida populations of Culex quinquefasciatus

Authors: Estep Iii, Alden; Sanscrainte, Neil; STUCK, JASON - Pinellas County Public Works; UNLU, ISIK - Miami-Dade County'S Mosquito Control; PRASAUSKAS, AGNES - Pasco County Mosquito Control; MUNDIS, STEPHANIE - University Of Florida; COTTER, NICHOLAS - Lee County Mosquito District; ROMERO-WEAVER, ANA - University Of Florida; FEDIRKO, T.J. - University Of Florida; KENDZIORSKI, NATALIE - University Of Florida; KOSINSKI, KYLE - University Of Florida; RAMIREZ, DAVIELA - University Of Florida; BUCKNER, EVA - University Of Florida

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/6/2024
Publication Date: 3/15/2024
Citation: Estep III, A.S., Sanscrainte, N.D., Stuck, J., Unlu, I., Prasauskas, A., Mundis, S., Cotter, N., Romero-Weaver, A., Fedirko, T., Kendziorski, N.L., Kosinski, K.J., Ramirez, D., Buckner, E.A. 2024. The 1014F knockdown resistance mutation is not a strong correlate of phenotypic resistance to pyrethroids in Florida populations of Culex quinquefasciatus. Insects. 15(3):197. https://doi.org/10.3390/insects15030197.
DOI: https://doi.org/10.3390/insects15030197

Interpretive Summary: Previous studies have shown many populations of Culex quinquefasciatus are resistant to pyrethroids, the most common class of pesticide used by public health agencies. A genetic mutation (L1014F) has been identified in previous studies as contributing to this insecticide resistance but the value of using this as a surrogate marker for phenotypic resistance is unclear. To examine this question, mosquitoes from more than 70 locations across Florida (the largest US study to date) were tested to assess the correlation between standard resistance bioassays and L1014F mutation to determine if the mutation is a useful surrogate to assess insecticide resistance. Results from these Culex quinquefasciatus populations indicate that this mutation is only a moderate strength correlate of resistance and is thus unlikely to be a good surrogate for estimating resistance.

Technical Abstract: Culex quinquefasciatus is an important target for vector control because of its ability to transmit pathogens that cause disease. Most populations are resistant to pyrethroids and often to organ-ophosphates, the two most common classes of active ingredients used by public health agencies. A knockdown resistance (kdr) mutation, resulting in a change from a leucine to phenylalanine in the voltage gated sodium channel, is one mechanism contributing to the pyrethroid resistant phe-notype. Enzymatic resistance has also been shown to play a very important role. Recent studies have shown strong resistance in populations even when kdr is relatively low which indicates factors other than kdr may be larger contributors to resistance. In this study, we examined on a statewide scale (over 70 populations), the strength of the correlation between resistance in the CDC bottle bioassay and the kdr genotypes and allele frequencies. Spearman correlation analysis showed only moderate (-0.51) and weak (-0.29) correlation between the kdr genotype and permethrin and deltamethrin respectively. The frequency of the kdr allele was an even weaker correlate. These results indicate, in contrast to Aedes aegypti, assessing kdr in populations of Culex quinquefasciatus is not a good surrogate for phenotypic resistance testing.