RESUMO
Hard tick infestation is an important problem in both traditional and industrial animal husbandry as well as in veterinary and public health. Several acaricides have been used to control tick infestation in Iran. Poor control has been attributed to acaricide resistance in tick populations although this has not been demonstrated experimentally. In this study, susceptibility status to propetamphos (Blotic) of 2-3-week-old larvae of Rhipicephalus bursa, one of the most common tick species in Iran, was evaluated using the FAO recommended larval packet test (LPT) method with some modifications. Log dosage probit analysis of propetamphos dose-response regression lines produced a resistance ratio based on LC(50) in the most resistant strain of approximately 103-fold. Biochemical assays suggested that the tick strains contained multiple insecticide resistance mechanisms involving elevation of esterases, GSTs, MFOs and alteration of acetylcholinesterase. In light of this data, practical implications for pest and pesticide resistance management strategies are discussed.