Resistance to pyrethroid insecticides and analysis of knockdown resistance (kdr) gene mutations in Aedes albopictus from Haikou City / 第二军医大学学报

ABSTRACT

Objective To investigate the resistance to deltamethrin and permethrin in Aedes albopictus in Haikou City, and to detect the knockdown resistance (kdr) mutants of A. albopictus, elucidating the association of resistant phenotype with kdr mutation. Methods The A. albopictus samples were collected from Xinfu Island, Longtang Town, Shishan Town, Baishamen Park, and the flower market in Haikou City. Their susceptibility to deltamethrin and permethrin was tested by larval bioassay. The resistance level was determined by the R/S ratio. The kdr gene was amplified and analyzed, and the relationship between the resistant phenotype and kdr mutation was determined by Chi-square test. Results The A. albopictus samples from the flower market and Baishamen Park showed resistance to deltamethrin and permethrin, of which the flower market population had an R/S ratio of up to 436.36, indicating a high level of resistance. The A. albopictus samples from Longtang Town and Shishan Town were sensitive to permethrin, but had low (R/S ratio, 9.09) and moderate (18.18) degrees of resistance to deltamethrin, respectively. The Xinfu Island population was sensitive to both deltamethrin and permethrin. The codon 1 534 kdr was detected point mutations among 317 A. albopictus samples, with two mutant alleles, TGC/C and TCC/S. The five genotypes were wild-type TTC/TTC (frequency, 62.15%), wild/mutant heterozygous TTC/TGC (0.63%) and TTC/TCC (16.09%), homozygous mutant TCC/TCC (20.82%), and mutant heterozygous TGC/TCC (0.32%). Chi-square test revealed significant differences in the frequency of kdr mutant genotype between A. albopictu sensitive to the insecticides (31.97%) and those resistant to the insecticides (42.94%), P <0.05. Conclusion Some A. albopictus populations in Haikou City have developed resistance to both deltamethrin and permethrin. The resistant phenotype and kdr mutant genotype are closely associated. This study has also discovered for the first time the novel TCC/S point mutation of kdr.