Molecular and Biochemical Detection of Insecticide Resistance in the Leishmania Vector, Phlebotomus papatasi (Diptera: Psychodidae) to Dichlorodiphenyltrichloroethane and Pyrethroids, in Central Iran

The aim of the present study was to explore resistance markers and possible biochemical resistance mechanisms in the Phlebotomine sand fly Phlebotomus papatasi in Esfahan Province, central Iran. Homogenous resistant strains of sand flies were obtained by exposing P. papatasi collected from Esfahan to a single diagnostic dose of DDT. The adults from the colony were tested with papers impregnated with four pyrethroid insecticides: Permethrin 0.75%, Deltamethrin 0.05%, Cyfluthrin 0.15%, and Lambdacyhalothrin 0.05% to determine levels of cross-resistance. To discover the presence of mutations, a 440 base pair fragment of the voltage gated sodium channel (VGSC) gene was amplified and sequenced in both directions for the susceptible and resistant colonies. We also assayed the amount of four enzymes that play a key role in insecticide detoxification in the resistant colonies. A resistance ratio (RR) of 2.52 folds was achieved during the selection of resistant strains. Sequence analysis revealed no knockdown resistance (kdr) mutations in the VGSC gene. Enzyme activity ratio of the resistant candidate and susceptible colonies were calculated for α-esterases (3.78), β-esterases (3.72), mixed function oxidases (MFO) (3.21), and glutathione-S-transferases (GST) (1.59). No cross-resistance to the four pyrethroids insecticides was observed in the DDT resistant colony. The absence of kdr mutations in the VGSC gene suggests that alterations in esterase and MFO enzymes are responsible for the resistant of P. papatasi to DDT in central Iran. This information could have significant predictive utility in managing insecticide resistant in this Leishmania vector.