Monitoring and prevention as a way to control poultry red mite (Dermanyssus gallinae) in organic layers
Dermanyssus gallinae, the poultry red mite (PRM), is highly relevant with respect to both animal welfare and economics in laying hen housing. The prevalence of D. gallinae in Europe and other parts of the world is very high and cause high economics losses which estimated by 130 million per year for the EU egg industry (Sparagano et al., 2014). In semi intensive farming systems such as barns, free range or organic farming often a higher prevalence rate could be observed due to better hiding places for D. gallinae in these more complex housing systems. Due to developments of resistances and current and future expected legal regulations, treatment options are limited in the EU, especially in organic production systems. Alternatives to chemical acaricides for control of D. gallinae are silica products, which are based on silicon dioxide. The acaricidal effect of such products desiccation after absorbing lipids from their cuticle (Mewis and Ulrichs, 1999; Akbar et al., 2004; Schulz et al., 2014). Silica products have a low oral toxicity (Islam et al., 2009) and there is no safety concern for silicon dioxide intake up to 1500 mg SiO2 per day for humans (EVM, 2003). Furthermore, they are registered and approved as a food additive (EFSA, 2009) and silica products can be applied in the presence of hens at high infestation with D. gallinae in practice. In practice, there is a large variety of methods to apply silica products. Thus, we investigated schedules of application of silica products in organic layer farms. In addition, we tested the efficacy of some products under field conditions throughout laying period.