An in vitro evaluation of the sensitivity and responses of Dermanyssus gallinae to selected acaricides.

Dermanyssus gallinae is an obligatory ectoparasite of birds which feeds on blood and significantly compromise the well-being of commercially raised laying hens. In this study, the mortality rates and responses of D. gallinae to 2 acaricides with a physical mode of action (Dergall and Mite Max) and 2 acaricides with a chemical mode of action (Milben Ex and Bio PK) were evaluated in tree dilutions (S1-3) and compared at 8-time intervals after application. The evaluation involved a novel method that simulates real-world conditions in a commercial poultry farm. Tested products have shown high efficacy (84.3-100%) against D. gallinae in the producer recommended solution (S1). Acaricides with a physical mechanism of action were as effective as chemical agents in eradicating poultry red mites. The compared preparations differed only in the onset of action which was longer in acaricides with a physical mode of action (1-6 h for chemical 24 h for physical in S1). An increase in the concentration of the active ingredient did not significantly speed up the onset of action of the evaluated preparations. However, the efficacy of Dergall and Bio PK decreased when the applied dose was halved, to 12% and 0% respectively. A decrease in the dose Mite Max led to a somewhat smaller, but not statistically significant decrease in mite mortality rates (74%). The proposed method for evaluating acaricide efficacy can be helpful in selecting the most effective preparations and the optimal concentration of the working solution to be applied in commercial layer farms, thus reducing the costs associated with the eradication of D. gallinae. The developed method enables a reliable evaluation of acaricides with both a physical and chemical mode of action, and it supports observations of the parasites' responses to the applied treatment.