Efficacy of Phoxim 50 % E.C. (ByeMite) for treatment of Dermanyssus gallinae in laying hens under field conditions

A GCP-controlled, randomised and blind trial used 2 layer houses naturally infested with D. gallinae. One house with space for 23,000 hens was treated with an aqueous solution (2,000 ppm Phoxim, 25 ml/hen place) twice 7 days apart. The second house with space for 21,000 hens was not treated. For quantitative assessment of mite population, 20 cardboard traps per house were deployed onto the cages for 24 hours on Days –1, 2, 6, 9, 13, 20, 34 and 48 in both houses. The mite population had decreased by 91 % on D3. Efficacy on D7 was 88.5 % and remained > 97 % from D10 until D49. There was a drop in egg production the day following the first and the second treatment in both buildings, but it was not treatment-related. Finally, the egglaying rate was similar in both groups. The mean number of dead hen was significantly higher in the control group (0.6 %) than in the treatment group (0.4 %). A maximum residue level for chicken meat and eggs has been granted by EMEA in January 2005 and data have been submitted to the authorities to approve a 0-day withdrawal period for eggs.