Insecticide Resistance Mechanisms in the Adult Phlebotomus papatasi (Diptera: Psychodidae) to Pyrethroid and Dichlorodiphenyltrichloroethane (D.D.T) Esfahan province, Iran.

Background: The major mechanisms of D.D.T resistance in insects are knock down resistance mutations (kdr) within the para voltage-gated sodium channel gene in nerve cells (Vgsc). Resistance to each group of insecticide is associated with increased concentrations of specific enzymes or altered target sites.Objectives: The present study reports the results of time-mortality bioassay to D.D.T 4%, lambda-cyhalothrin 0.05%, permethrin 0.75%, cyfluthrin 0.15% and deltamethrin 0.05% in recently colonized & field P. papatasi populations in Iran. In the present study a region of in the para voltage-gated sodium channel gene of P. papatasi was sequenced. A biochemical assay was used to evaluate insecticide resistance by measuring the activity levels of detoxification enzymes in sand flies.Materials and Methods: Baseline susceptibility to D.D.T and pyrethroids was assessed on specimens collected from the study area& sand flies that colonized. The selection is performed by a sub lethal time of D.D.T exposure until a homogeneous resistant strain. The PCR products were purified with the QIA quick PCR purification kit (Qiagen) and sequenced (in forward and reverse directions). The colorimetric method was used to determine the quantity of four enzymes responsible for the detoxification of insecticides.Results: The selection continues to Resistance Ratio = RR more than 2.52folds. Sequence analysis was performed on 440 base pair long fragments of voltage-gated sodium channel gene. Enzyme ratio calculated for two population of Resistance candidate & susceptible were 3.78, 3.72, 3.21, and 1.59 for α-esterase, β-esterase, and MFO and GST enzyme, respectively.Conclusion: The comparison of the region including kdr mutations in exon and locus 1014 showed that in all three populations there is a TTA sequence, the mutation of type kdr in resistant populations that is not due to the substitution of the TTA to the TTT. This study showed that the altered enzymes are responsible for D.D.T resistance in P.papatasi in central parts of Iran.