Effect of triflumuron, a chitin synthesis inhibitor, on Aedes aegypti, Aedes albopictus and Culex quinquefasciatus under laboratory conditions

Background: Resistance to traditional insecticides represents a threat to the control of disease vectors. The insect growth regulators (IGR) are a potential alternative to control mosquitoes, including resistant populations. The chitin synthesis inhibitors (CSI) are IGRs, which interfere with the insect molting process and represent one major class of compounds against Aedes aegypti populations resistant to the larvicide organophosphate temephos. In the present study, we evaluated the efficacy of the CSI triflumuron on Culex quinquefasciatus, Aedes albopictus and against several Ae. aegypti field populations.

Methods: The efficacy of triflumuron, against Cx. quinquefasciatus and Ae. albopictus was evaluated with laboratory strains through dose-response assays. Additionaly, this CSI was tested against seven Ae. aegypti field populations exhibiting distinct resistance levels to both temephos and the pyrethroid deltamethrin. Aedes aegypti populations were exposed to both a dose that inhibits 99% of the adult emergence of mosquitoes from the susceptible reference strain, Rockefeller, (EI₉₉ = 3.95 μg/L) and the diagnostic dose (DD), corresponding to twice the EI₉₉.

Results: Our results indicate that triflumuron was effective in emergence inhibition (EI) of Cx. quinquefasciatus (EI₅₀ = 5.28 μg/L; EI₉₀= 12.47 μg/L) and Ae. albopictus (EI₅₀ = 1.59 μg/L; EI₉₀= 2.63 μg/L). Triflumuron was also effective against seven Ae. aegypti Brazilian populations resistant to both temephos and deltamethrin. Exposure of all the Ae. aegypti populations to the triflumuron EI₉₉ of the susceptible reference strain, Rockefeller, resulted in complete inhibition of adult emergence, suggesting no cross-resistance among traditional insecticides and this CSI. However, a positive correlation between temephos resistance and tolerance to triflumuron was observed.

Conclusion: The results suggest that triflumuron represents a potential tool for the control of disease vectors in public health. Nevertheless, they point to the need of constant monitoring of the susceptibility status of vector populations to CSIs.