Table 1_Genetic variations in three insecticide targets in the disease vector Culex quinquefasciatus from Mianyang, China: simultaneous detection of novel mutations RDL A296G and VGSC A1007T.docx

Culex quinquefasciatus is a major vector of filariasis and Japanese encephalitis in China. The application of insecticides is a regular measure for prevention and control of such mosquito-borne diseases. However, insecticide resistance, often caused by target-site mutations, threatens control efforts. In Mianyang City, a region previously reporting high pyrethroid resistance, the current genetic basis of resistance remains unclear. To address this gap, resistance-related mutations in three key insecticide targets, including acetylcholinesterase (AChE, encoded by ace1, conferring organophosphate/carbamate resistance), GABA receptor RDL subunit (encoded by rdl, conferring dieldrin/fipronil resistance), and voltage-gated sodium channel (VGSC, encoded by vgsc, conferring pyrethroid/DDT resistance), in seven field populations of Cx. quinquefasciatus collected across Mianyang were simultaneously screened by gene sequencing. The results showed that the known AChE G119S mutation was present at low frequencies (1.25% to 5.1%). Two RDL mutations, the previously reported A296S and a novel A296G, were widely detected at appreciable frequencies. In the vgsc gene, the knockdown resistance allele L1014F was dominant (overall frequency 88%), and a novel A1007T mutation emerged on the L1014F allele. This study provides the first comprehensive snapshot of co-existing target-site resistance mutations in Cx. quinquefasciatus. The simultaneous presence of mutations across three distinct target mechanisms, including two first-reported mutations (RDL-A296G and VGSC-A1007T), signals a multifaceted and evolving resistance landscape. These findings highlight an urgent need for resistance monitoring and management in this important disease vector.