Evaluating the susceptibility of malaria vectors to the new WHO-recommended products is a key step before large-scale deployment. In the present study, Tatiane ASSATSE and collaborators mapped the susceptibility profile of one of the major malaria vectors, Anopheles funestus, to neonicotinoids insecticides across Africa and they established the diagnostic doses of acetamiprid and imidacloprid (other neonicotinoids insecticides) with acetone+MERO as solvent. To achieve that, they collected Indoor resting An. funestus in Cameroon, Malawi, Ghana, and Uganda. Susceptibility (mosquitos’ mortality) to clothianidin, imidacloprid, and acetamiprid diluted in three different solvents (absolute ethanol, acetone, and acetone+MERO) was evaluated using CDC bottle assays and offsprings of the field-caught adults. They also genotype the L119F-GSTe2 to assess the potential cross-resistance between clothianidin and this DDT/pyrethroid-resistant marker. As result, they observed a high mortality of mosquitoes exposed to all three neonicotinoids diluted in acetone + MERO, whereas low mortality was noticed with ethanol or acetone alone. The doses of 6 µg/mL and 4 µg/mL were established as diagnostic concentrations of imidacloprid and acetamiprid respectively, with acetone combined with MERO. Pre-exposure to synergists significantly restored the susceptibility of mosquitoes to clothianidin. Also,a positive correlation was observed between the L119F-GSTe2 mutation and clothianidin resistance with the homozygote resistant mosquitoes being more able to survive than heterozygote or susceptible.
This study revealed that An. funestus populations across Africa are susceptible to neonicotinoids, and as such, this insecticide class could be effectively implemented to control this species using Indoor Residual Spraying (IRS). However, potential cross-resistance conferred by GSTe2 calls for regular resistance monitoring in the field.
Read more : https://doi.org/10.3390/tropicalmed8050244
