Development of a standardised laboratory test with dung beetles for the assessment of the ecotoxicity of veterinary pharmaceuticals
According to European law, the environmental risk assessment of veterinary pharmaceuticals for dung beetles is required for parasiticides for the treatment of pasture animals. Starting with recommendations from the SETAC advisory group DOTTS (Dung Organism Toxicity Test Standardisation), a test system using the widespread temperate dung beetle species Aphodius constans was developed. Together with the University of Montpellier culturing and testing of A. constans were investigated in a project sponsored by the German Federal Environment Agency (UBA). The survival of first instar larvae of A. constans exposed to the test substance spiked into formulated (i.e. dried, grounded and re-wetted) or fresh dung is measured over a period of three weeks. Using the model substance dimethoate (an insecticide required as positive control in tests with the predatory mite Hypoaspis aculeifer) the suitability of the new dung beetle test was verified. Afterwards, the new test method was used to determine the toxicity of four common veterinary pharmaceuticals (ivermectin, dicyclanil, moxidectin, praziquantel) in formulated and fresh dung. The effects of ivermectin on the dung beetles were determined in a test using fresh dung from treated cattle. Differences in the toxicity in fresh and formulated dung were small. For ivermectin and moxidectin, the test results are in the same order of magnitude as those known from other studies. Effects of ivermectin on ecologically relevant dung beetles gained in a standardised test method reflect the results from field studies and are in the range of environmentally relevant concentrations. The test method has been described in detail in an OECD Guidance Document (2010).