Insecticides Resistance Surveillance For Dengue Vector Aedes In China And Data Analyses

Dengue outbreak frequently occurred in China in recent years, including outbreaks in Guangdong Province (2014), Chaozhou (2015) and Jinghong, Yunnan Province (2015). The dengue outbreak highlights the great pressure in dengue control and prevention. Lacking of efficient treatment and vaccines for dengue, the main method to control dengue outbreak remains on the chemical insecticides. However, the extensively use of insecticides not only leads to environmental contamination but also favors the development of insecticides resistance. Consequently, the efforts we put in dengue control and prevention will be greatly undermined by the high resistance. And it is crucial for us to have the insecticides resistance supervised and monitored closely.In this study, we used a stain of Aedes albopictus that have been reared in our laboratory for many years without exposure to any insecticides as reference stain. Thorough bioassays, larvae were tested against 14 insecticides; adult were against 13 insecticides. Enzymatic susceptibility was also tested on both larval and adult Ae. albopictus, including non-specific esterase (NSE), mixed function oxidase (MFO) and glutathione S-transferase (GST). Furthermore, we collected mosquitoes from Guangzhou and Chaozhou during dengue outbreak, and tested the susceptibility to commonly used insecticides.In addition, to have a comprehensive view of the resistance status of Aedes in China, we searched literature on insecticides resistance in China, and collected the data and analyzed. Specifically, we analyzed the temporal and spatial distribution of resistance to deltamethrin, permethrin and dichlorvos, and visualized them on maps. Then aided by SaTscan, we identified the high resistance area and low resistance area in China. The results of the study were summarized as following:1. the larval LC50 of reference strain were:cypermethrin 0.1909×10-3mg/L, cyhalothrin 0.6415×10-3mg/L, malathion 0.0129mg/L, dichlorvos 0.0381mg/L. azamethiphos 0.0438mg/L. fenobucarb 0.2004mg/L. propoxur0.3641mg/L. DDT 0.0293mg/L. Acetofenate 0.071 Omg/L. The adult of LC50 of the reference strain were:cyhalothrin (0.0207%). alpha-cypermethrin (0.0272%). cypermethrin (0.0342%). beta- cypermethrin (0.0355%), dichlorvos (0.0577%), malathion (0.1209%), temephos (1.3720%), propoxur (0.0040%), fenobucarb (0.0135%), and DDT (2.8270%). We also tested the enzymatic activity of GST, NSE and MFO, and revealed as 37.43 nmol/(minmg Pr)、132.80 nmol 3-Acetoxy-2-naphthanilide/(mining Pr) and 0.621 nmol cyt c/mg Pr, respectively for larvae; 41.42 nmol/(minmg Pr).64.38 nmol 3-Acetoxy-2-naphthanilide/(minmg Pr) and 0.468 nmol cyt c/mg Pr, respectively for adults.2. The susceptibility of Ae. albopictus collected from Guangzhou and Chaozhou were tested, and showed high resistance to pyrethroids. Notably, the larvae collected from Huangpu District in Guangzhou had developed 262 folds’resistance of reference strain to cypermethrin, and larvae from Chaozhou showed 1032.8 folds’resistance to permethrin. By contrast, the mosquitoes were sensitive or low resistant to organophosphates and carbamates.3. Based on the analyses of the insecticide resistance database, Ae. albopictus has showed a progressive resistance to deltamethrin, permethrin and dichlorvos in recent couple of years. Spatially, an area centered at Guangzhou, radius at 522.03 km was identified as the high resistance zone using Satscan. On the other hand, mosquitoes from Northern China and parts of Hainan Province were relatively low insecticides resistance.This study revealed high insecticides resistance of Ae. albopictus to pyrethroids, while low resistance to organophosphates. The high resistance area was identified at Guangzhou Province and its vicinity.