Effects of fluazuron and ivermectin treatment of cattle on the structure of dung beetle communities

A long-term and large-scale field study was carried out to assess the ecotoxicological effect on the dung beetle fauna of cattle treatment with ivermectin (broad-spectrum endectocide) and fluazuron (acaricide) under normal extensive farming conditions in South Africa. One herd of 25 heifers was treated four times at an 8-week interval (starting late November 2001) with a standard injection of ivermectin (200 μg/kg) and a standard pour-on dosage of fluazuron (3 mg/kg) and another herd was left untreated as a control. This set-up was replicated on a second, separate farm and the four herds were kept in four separate paddocks of about 80 ha each. Dung beetle communities were monitored over an entire farming season, from early November 2001 until August 2002. This study was carried out in a very moist year with above average rainfall. The impact of the treatment on the dung beetle communities was examined using a variety of community measures as well as a wide range of univariate, graphical and multivariate analyses. There was no observable effect of the administered drugs on the dung beetle communities. Species richness and diversity seemed unaffected in the treated communities and the ecological similarity of the treated and control communities remained high through most of the trial. These results support the notion that the ecotoxicological impact of antiparasitic drugs depends on factors such as climatic conditions, spatial scale of treatment and proportion of animals treated.