Field effects of ivermectin residues on dung beetles.
Abstract
The effects and the persistence of a single sc injection of ivermectin (Ivomec) to steers, at the recommended dose rate of 200 µg/kg body weight, were studied in field experiments in Spain in spring 1990. Elimination of ivermectin by cattle (in faeces) was rapid (within 12 days), with a peak on day 5 (0.42 mg/kg). The persistence of ivermectin in dropped dung was low under field conditions (<6 days). The drug itself did not increase attraction of beetles to dung. The attraction of beetles to dung from treated animals increased after day 5 until day 17, beyond the time when ivermectin was available. It is suggested that ivermectin modified the gut flora of treated cattle after the peak of elimination. Watering of pats did not influence results. Ivermectin levels in dung dropped on days 1 and 10 post-treatment inhibited the development of larvae of the dung-dwelling Diptera Neomyia cornicina. Dung dropped on day 1 inhibited the development of the dung beetle Euoniticellus fulvus [Oniticellus fulvus], but dung dropped on day 10 only caused a slight delay in development. The consequences of routine treatment of cattle with ivermectin on non-target organisms are discussed.