Background: The poultry red mite, Dermanyssus gallinae known as the most important bloodfeeding parasite of poultry in the world affecting egg layer and breeder flocks. This mite represents a significant threat to egg production industry in many parts of the world including Iran. The extensive and improper use of chemical compounds in infected poultry houses can lead to developing resistance of this parasite. The aim of this study was to evaluate the susceptibility of D. gallinae to Phoxim, Sevin and Cypermethrin under laboratory conditions. Methods: Five infested poultry farms were sampled and collected D. gallinae mites transferred to parasitology laboratory. Samples from each poultry farm (each batch including 25 mites) were individually exposed to the concentrations of 0.001, 0.01, 0.1 and 1v/v of Phoxim, Cypermethrin and Sevin, according to contact test invented by Thind and Muggleton 1998 for 24 h; after which the test cells were opened and live and dead mites were counted. Results: The effectiveness of cypermethrin in all studied poultry farms was very low and the highest mean efficacy of this acaricide was 20.19% in poultry farm A. In other sampled poultry farms, determined efficacy for Cypermethrin was less than 10%. Phoxim in one sampled poultry farm (B) had an effectiveness of 79.61%, but in other farms, its efficiency was more than 90%. Sevin also had a relatively high efficacy and the lowest efficacy was observed for poultry farm B (55.04%) and in other poultry farms its efficiency was more than 70%. Conclusion: The results of this study showed that D. gallinae sampled from five studied farms was significantly resistant to Cypermethrin. The results also revealed that Sevin in low concentrations did not has proper efficacy but the most of D. gallinae mites sampled from five poultry farms were susceptible to Phoxim.

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