[Deltamethrin resistance, metabolic detoxification enzyme and kdr mutation in Anopheles sinensis in region along Huaihe River in Anhui Province].

OBJECTIVE: To understand the deltamethrin resistance level, GTS and P450 metabolic detoxification enzyme activities, and mutations in the para-type sodium channel gene that confers knockdown resistance (kdr) in Anopheles sinensis mosquitoes from malaria endemic areas along the Huaihe River in Anhui Province, China. METHODS: An. sinensis adult mosquitoes were collected in Lilou, Mohekou and Tuohu townships of Bengbu City, Anhui Province from August to September, 2011. The insecticide resistance bioassays were performed on adult mosquitoes by using the standard WHO susceptibility test with diagnostic concentrations of deltamethrin 0.05%, and the mosquito resistance status was classified based on the WHO resistance classification criteria. The metabolic detoxification enzyme activities were measured in randomly selected mosquitoes, and the IIS6 region of the para-type sodium channel gene was amplified by PCR and sequenced to detect mutations at the codon 1014. RESULTS: The knockdown rates within 60 min exposure to deltamethrin test paper were 4.1%, 7.0% and 8.2%, and the mortality rates were 8.2%, 12.0% and 12.8% for mosquitoes collected from Lilou, Mohekou and Tuohu townships, respectively. These three populations were classified as highly resistant populations based on the WHO resistance classification criteria. The GST and P450 enzyme activities of the three populations were significantly higher than those of the susceptible laboratory population (P < 0.001). L1014C and L1014F mutations were detected, and the wild type homozygote kdr genotype was not found. These three populations exhibited a small but insignificant difference in kdr allele frequencies. No mutation was found in the laboratory susceptible mosquitos. CONCLUSION: The An. sinensis mosquito populations from the regions along the Huaihe River in Anhui Province are strongly resistant to pyrethroid insecticides, and exhibit significantly higher metabolic detoxification enzyme activities than the laboratory susceptible population. The high frequency of kdr mutation is identified in the mosquito populations from the region along the Huaihe River in Anhui Province, China.