Laboratory selection of Aedes aegypti field populations with the organophosphate malathion: Negative impacts on resistance to deltamethrin and to the organophosphate temephos

摘要

Author summary Dengue, Zika and chikungunya viruses affect millions of people worldwide. Due to the lack of specific antivirals or to the limited supply of vaccines, focus remains on the control of the main vector, Aedes aegypti. Although the importance of social participation in the elimination of A. aegypti breeding sites is increasingly recognized, chemical control is still an important component of vector control. The exaggerated use of insecticides results in the spread of resistance and, consequently, in the loss of their effectiveness. In Brazil, malathion is the last adulticide available to the control of A. aegypti, due to the widespread resistance to pyrethroids. In order to anticipate what could occur in the field, we exposed two vector populations to selection with malathion. Both malathion and temephos, a larvicide largely employed, are organophosphates; however, they are structurally distinct molecules and seem to elicit different resistance mechanisms. We confirmed this issue: selection with malathion had a negative impact on temephos resistance compared to groups reared without any insecticide. Indeed, the variety of responses of both vector populations to the various insecticides points to the participation of multiple resistance mechanisms and confirms previous assumptions regarding the difficulty of identifying diagnostic insecticide resistance mechanisms.