Entwicklung und Einsatz eines standardisierten Labortests für Dungkäfer (Aphodius constans) zur Prüfung der Ökotoxizität von Veterinärpharmaka

Goal, Scope, and Background

According to European legislation, an environmental risk assessment of veterinary pharmaceuticals for dung beetles is required if the substance is a parasiticide for the treatment of pasture animals. However, the demonstration of the environmental safety of those substances for dung beetles is strongly hampered by the fact that no standardized test system is available so far. Therefore, starting with recommendations from the SETAC advisory group DOTTS (Dung Organism Toxicity Test Standardization), a test system using the widespread temperate dung beetle species Aphodius constans was developed.

Methods

Using experiences gained at the University of Montpellier (e.g. in field studies) and in other terrestrial tests, details of culturing and testing of A. constans were investigated in a project sponsored by the German Environment Protection Agency (UBA). Basically, the survival of young 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 test was checked. 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. Finally, the effects of ivermectin on the dung beetles were determined in a test using fresh dung from treated cattle.

Results and Conclusions

For Dmethoate LC₅₀-values were found in a range of 1–3 mg a.s./kg dung (dew.), depending on the dung type. Praziquantel did not show eirecis in the tested concentration range (i.e. up to 1000 mg a.s./kg Dung (DW). The LC₅₀-values of the other three pharmaceuticals were very low (<6 mg a.s./kg dung (DW)). With the exception of Dicyclanil no differences between formulated and fresh dung were identified. In the case of ivermectin the LC₅₀-value were even lower: about 0.5 mg a.s./kg dung (DW). No differences between the results of test in which the substance was spiked into dung and those tests which were performed with dung from treated cattle were found. These results prove the sensitivity as well as the robustness of this test method.

Recommendations and Perspectives

Based on the experiences reported here, it is recommended to standardize this test in an international ring test so that it can be incorporated in the risk assessment process for veterinary pharmaceuticals as described in the currently developed international registration guidelines.     

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