Abstract
BackgroundThe wetlands used for some agricultural activities constitute productive breeding sites for many mosquito species. Thus, the agricultural use of insecticide targeting other pests may select for insecticide resistance in malaria mosquitoes. The purpose of this study is to clarify some knowledge gaps on the role of agrochemicals in the development of insecticide resistance in malaria vectors is of utmost importance for vector control.MethodsUsing the CDC bottle test and the log-probit analysis, we investigated for the first time the resistance levels of Anopheles coluzzii mosquitoes to neonicotinoids, insecticides used exclusively for crop protection in Côte d’Ivoire. The study was conducted in two agricultural regions (Tiassale and Gagnoa) and one non-agricultural region (Vitre) between June and August 2017 using clothianidin, acetamiprid and imidacloprid.ResultsMosquito populations from Tiassale and Gagnoa (agricultural settings) were determined to be resistant to acetamiprid with mortality rates being < 85% at 24 h post-exposure. In Vitre (non-agricultural area) however, the mosquito population was susceptible to acetamiprid. In all three localities, mosquito populations were resistant to imidacloprid (mortality rates were 60% in Vitre, 37% in Tiassale, and 13% in Gagnoa) and completely susceptible to clothianidin (100% mortality). An. coluzzii represented 100% of mosquito collected in Gagnoa, 86% in Tiassale and 96% in Vitre.ConclusionsThis study provides strong evidence that agricultural use of insecticides can cause insecticide resistance in malaria vector populations. Insecticide resistance driven by agrochemical usage should be considered when vector control strategies are developed.
Highlights
The wetlands used for some agricultural activities constitute productive breeding sites for many mosquito species
Via log-probit analysis, and the Resistance Ratio (RR) calculated as the KDT50 of the wild strain divided by the KDT50 of the susceptible Kisumu strain. Diagnostic doses It appeared that 50 μg/bottle of clothianidin, 75 μg/bottle of acetamiprid, and 200 μg/bottle of imidacloprid were the minimum concentrations that caused 100% mortality on the susceptible Kisumu strain at 24 h post-exposure after a minimum of 30 min exposure for clothianidin and 1 h exposure for both acetamiprid and imidacloprid in Center for Disease Control (CDC) bottles
Knockdown and resistance ratio Knocked down mosquitoes were recorded for both acetamiprid and imidacloprid insecticides tested in the three localities, which rendered possible the determination of Resistance Ratios (RR), (Table 1)
Summary
The wetlands used for some agricultural activities constitute productive breeding sites for many mosquito species. The agricultural use of insecticide targeting other pests may select for insecticide resistance in malaria mosquitoes. The neonicotinoid family is composed of eight active ingredients which includes imidacloprid, thiamethoxam, thiacloprid, nitenpyram, acetamiprid, clothianidin, dinotefuran and nithiazine. These have a unique mode of action from other insecticides currently used in public health, their potential value in resistance management. Their pest spectrum, systemic activity and relatively low risk to non-target organisms have resulted in their widespread use. They constituted more than 25% of the insecticides sold globally in 2014 [2]. While it is currently the most widely-used neonicotinoid, several others have been developed and implemented since its inception
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