Monitoring of Dermanyssus gallinae in free-range poultry farms.

Various methods for monitoring Dermanyssus gallinae infestations within free-range egg production units were compared. The study was carried out in five egg-producing free-range poultry buildings infested with D. gallinae. Each farm was divided into six zones (each zone including nest boxes, perches and duckboard) for placing two types of traps (corrugated cardboard and thick card traps) or examining dried droppings for presence of mites. Traps were removed 24 h later, placed into bags and mites were counted at the laboratory using binocular magnification. Droppings were also inspected by eye and mite numbers were estimated. All the methods used allowed us to detect mites although their efficacy differed. The number of mites collected was independent of the type of trap used. Examination of the droppings did not differentiate between buildings with differing mite populations. Placing traps in the nest boxes is a less reliable indicator than placing them on the perches. It appears that the most coherent method for evaluating the D. gallinae population within a free-range flock is to place thick card traps throughout the building, on perches favoured by birds.