Mechanism of resistance to pyrethroid insecticides in Culex quinquefasciatus in Xingyi City, Guizhou Province
- Author:
KONG Xuexue
;
WANG Dan
;
ZHOU Jingzhu
- Publication Type:Journal Article
- Keywords:
Culex quinquefasciatus;
insecticide resistance;
metabolic enzyme;
knockdown resistance gene;
Xingyi City
- From:
China Tropical Medicine
2025;25(3):323-
- CountryChina
- Language:Chinese
-
Abstract:
Objective To investigate the resistance levels of adult Culex quinquefasciatus mosquitoes to three commonly used pyrethroid insecticides in Xingyi City, Guizhou Province, as well as to examine the changes in metabolic detoxification enzyme activities and mutations in the knockdown resistance (kdr) gene thereby providing a scientific foundation for the prevention and control of Culex quinquefasciatus in the region. Methods In 2024, the larvae of Culex quinquefasciatus were collected from different locations in Xingyi and reared to adult mosquitoes in the laboratory, and their resistance to pyrethroid insecticides was determined using the adult mosquito contact tube method. Surviving samples (resistant population) from the resistance tests were examined for the activities of mixed function oxidase (MFO), glutathione-S-transferase (GST), and non-specific esterase (NSE) using a microplate reader. The genomic DNA of individual adult Culex quinquefasciatus mosquitoes was extracted, and the voltage-gated sodium channel (VGSC) gene fragment was amplified via PCR and sequenced to analyze the mutations in the kdr gene. Results The 24-h mortality rates of adult Culex quinquefasciatus exposed to 0.25% permethrin, 0.025% deltamethrin, and 0.025% beta-cypermethrin were 1.00%, 0%, and 0.88%, respectively, indicating all populations of Culex quinquefasciatus exhibited resistance to the three pyrethroid insecticides. The activity of MFO in permethrin-resistant population followed a normal distribution, while deltamethrin-resistant and cypermethrin populations exhibited skewed distributions. The resistance ratios (RRs) for the three populations were 1.17, 1.03, and 1.07 times, respectively, with no statistically significant differences in MFO activity between field populations and susceptible strains (all P>0.05). However, the GST activities of permethrin-resistant and beta-cypermethrin-resistant field populations were 1.06 and 1.45 times higher than those of sensitive strains (P<0.05). Sequencing of the VGSC gene fragments of adult Culex quinquefasciatus resistant to pyrethroid insecticides revealed that mutations occurred solely at 1014 locus, presenting two alleles: wild type TTA(L) (1.26%) and mutant TTT(F) (98.74%). Two genotypes were identified: wild/mutant heterozygotes L/F (2.52%) and mutant homozygotes F/F (97.48%). No statistically significant differences were observed in the frequency of resistance gene mutations among populations resistant to the three pyrethroid insecticides (P>0.05). Conclusion The adult mosquitoes of Culex quinquefasciatus in Xingyi have developed resistance to three commonly used pyrethroid insecticides, with changes observed in metabolic detoxification enzyme activities and mutations in the kdr gene. The resistance of Culex quinquefasciatus in Xingyi is the result of multiple mechanisms. Understanding the resistance level and mechanism can provide a reliable basis for mosquito control and resistance management. It is recommended to enhance the monitoring of mosquitoes' resistance to insecticides, prioritize environmental management focused on eradicating breeding sites, reduce the use of pyrethroid insecticides, and rotate with other classes of insecticides to delay the onset of resistance.
- Full text:202511171721263412611.Mechanism of resistance to pyrethroid insecticides in Culex quinquefasciatus in Xingyi City, Guizhou Province.pdf
