Short-term metabolic resistance inductive effect of different agrochemical groups on Anopheles gambiae mosquitoes

Context: In order to assess the impact of the different groups of agricultural pesticides used in Côte d'Ivoire on the increase of mosquitoes resistance to insecticides, the expression profiles of 7 P450 cytochromes and one GSTE2 of Anopheles gambiae involved in mosquito resistance to insecticides were studied.

Methods: Three groups of pesticides were selected: The first group is composed of agricultural insecticide solutions, the second is made up of none-insecticide pesticide solutions (a mixture of herbicides and fungicides) and the third group is made up of a mixture of the first two. A fourth non-pesticide solution was used as a control. Four groups of each stage 2 larvae were exposed to 20% concentrated solution for 24 hours. Susceptibility tests for DDT and Deltamethrin were carried out on adults aged 2-5 days. RT-qPCR was performed to quantify the expression of eight metabolic genes involved in mosquito resistance to insecticides. 

Results: Tests susceptibility to DDT showed a similar increase in the time required to down 50% of mosquitoes (kdt50) in l colonies exposed to insecticides and none-insecticides compared to the control colony. As for deltamethrin, kdt50 was higher in the colonies exposed to insecticides and the pesticide mixture compared to the colony exposed to none-insecticides. Of all the genes studied in all colonies, except for CYP6P1 induced only in the colony consisting of the pesticide mixture, no genes were induced.

Conclusion: This study confirmed that induction is influenced by the duration, the concentration of the solution and the type of xenobiotic used as an inducer. The overexpression of CYP6P1 confirmed the inductive effect that a short exposure of mosquito larvae to agricultural pesticides could have.