Multiple resistances and complex mechanisms of Anopheles sinensis mosquito: a major obstacle to mosquito-borne diseases control and elimination in China.

Joshua Hartsel,Linna Shi,Daibin Zhong,Qiang Fang,Guiyun Yan,Guofa Zhou,Xuelian Chang,Fujin Fang,Changliang Zhu

doi:10.1371/journal.pntd.0002889

Abstract

Malaria, dengue fever, and filariasis are three of the most common mosquito-borne diseases worldwide. Malaria and lymphatic filariasis can occur as concomitant human infections while also sharing common mosquito vectors. The overall prevalence and health significance of malaria and filariasis have made them top priorities for global elimination and control programmes. Pyrethroid resistance in anopheline mosquito vectors represents a highly significant problem to malaria control worldwide. Several methods have been proposed to mitigate insecticide resistance, including rotational use of insecticides with different modes of action. Anopheles sinensis, an important malaria and filariasis vector in Southeast Asia, represents an interesting mosquito species for examining the consequences of long-term insecticide rotation use on resistance. We examined insecticide resistance in two An. Sinensis populations from central and southern China against pyrethroids, organochlorines, organophosphates, and carbamates, which are the major classes of insecticides recommended for indoor residual spray. We found that the mosquito populations were highly resistant to the four classes of insecticides. High frequency of kdr mutation was revealed in the central population, whereas no kdr mutation was detected in the southern population. The frequency of G119S mutation in the ace-1 gene was moderate in both populations. The classification and regression trees (CART) statistical analysis found that metabolic detoxification was the most important resistance mechanism, whereas target site insensitivity of L1014 kdr mutation played a less important role. Our results indicate that metabolic detoxification was the dominant mechanism of resistance compared to target site insensitivity, and suggests that long-term rotational use of various insecticides has led An. sinensis to evolve a high insecticide resistance. This study highlights the complex network of mechanisms conferring multiple resistances to chemical insecticides in mosquito vectors and it has important implication for designing and implementing vector resistance management strategies.

Highlights

Malaria and filariasis are two of the most important vector-borne parasitic diseases in Southeast Asia
Diseasevector control is an important part of the global malaria and filariasis control strategies
Pyrethroid insecticides are the major vector control agents, and rotational or combinational use with other classes of insecticides has been proposed to mitigate the problem of pyrethroid resistance

Summary

Introduction

Malaria and filariasis are two of the most important vector-borne parasitic diseases in Southeast Asia. Malaria surveillance and vector control become very important tools to prevent malaria outbreaks in low-transmission areas [1]. Insecticide-treated bed nets (ITNs) and indoor residual spray (IRS) are the primary vector control tools in the Global Strategy for Malaria Control and the Roll Back Malaria program [2] and in the Global Fund to Fight AIDS, Tuberculosis and Malaria [3]. Pyrethroids are currently the only class of insecticide approved for use on ITNs [4] due to their high toxicity to insects, rapid rate of knockdown, strong mosquito excitorepellency, and low mammalian toxicity [5]. Insecticides remain the most important vector control method; insecticide resistance poses a major threat to vector-borne disease control due to lack of other viable alternatives

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Conclusion