First investigation of deltamethrin pyrethroid susceptibility and resistance status of Anopheles labranchiae (Falleroni, 1926), potential malaria vector in Tunisia

Abstract

Objective: To evaluate the deltamethrin pyrethroid insecticides against Anopheles labranchiae, potential malaria vector in Tunisia. Methods: Six field populations of Anopheles labranchiae mosquitoes were collected from six localities in Northern and Central Tunisia between October and November 2016. Different bioassays were performed to estimate the level of resistance in each collected population. Two synergists were used to estimate the involvement of detoxification enzymes in insecticide resistance. Results: All studied strains were resistant and the RR50 ranged from 12.5 in sample #1 to 72.5 in sample #6. Synergist tests using piperonyl butoxide indicated the involvement of monoxygenases enzymes in the recorded resistance. In contrast, the increase of deltamethrin mortality was not significant in presence of S,S,sributyl phosphorothioate (0.8 < SR < 1.2), suggesting no role of esterases (and/or GST) in the resistance phenotype. The correlation recorded between mortality due to DDT and the LC50 of deltamethrin insecticide indicated an insensitive sodium channel affected by Kdr mutation (Spearman rank correlation, r = −0.59, P < 0.01). Conclusions: These results should be considered in the current mosquitoes control programs in Tunisia. The use of pesticides and insecticides by both agricultural and public health departments in Tunisia should be more rational to reduce the development of resistance in populations. Different insecticide applications should be implemented alternately. Keywords: Resistance, Anopheles labranchiae, Deltamethrin pyrethroid, Synergism, Kdr mutation, Tunisia