Fitness cost in field Anopheles labranchiae populations associated with resistance to the insecticide deltamethrin

Abstract We evaluated in the present study the effect of deltamethrin resistance on the fitness cost of the filed populations of Anopheles labranchiae. A susceptible population was used as reference to do different comparisons. We selected the most resistant larvae population collected from northern Tunisia. Eggs were used for study of life history traits including developmental time, larvae mortality, fertility, hatchability and adult sex-ratio. Our results showed that deltamethrin resistance affected negatively (p < 0.05) the developmental time with the median range of 70 h, mortality with the rate of 7 folds in resistant population and hatchability which are lower than in susceptible population. Whereas, no significant differences were detected in adult sex-ratio and fertility of the two studied populations. Our results could help to determine the evolution of population dynamics of the resistant studied population in the areas where insecticide resistance is reported and resistance management is needed.

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

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 RRs0 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.