A Dutch survey on poultry red mite, which has also been conducted throughout Europe, showed the following results:
At around 80% of the laying-hen farms, red mites were seen. 32% of the
participating farms were able to find the red mites in cracks and crevices; a mild to moderate contamination. At 27% of the farms groups or clusters of mites were visible on the housing system, indicating a serious infection. Main treatments used against red mites were silica products and soaps. Most laying-hen farmers saw a decrease in the number of red mites after treatment, although only 14% of the respondents monitored the red-mite population. Treatments are especially applied when (the first) red mites are visible. Hygiene measures against red mites are mainly taken when the house does not contain laying hens. On average, poultry farmers spent € 0.15 / hen / production period of 73 weeks (min-max; € 0.0005 – € 0.67). It is not possible to draw firm conclusions based on this survey because only 44 farmers responded, i.e. 5% of the total number of Dutch layer farms
The report can be found here (in Dutch).