Effects of ivermectin in dairy discharges on terrestrial and aquatic invertebrates

Abstract

Ivermectin (22,23-dihydroavermectin B₁) is a broad-spectrum antiparasitic drug that was introduced for the control of parasitic worms and lice in sheep and cattle. This review summarises what is known about the impact of ivermectin in pastures and catchments and also on freshwater systems. Differing results have been obtained for the effects on decomposition of dung from ivermectin-treated cattle, although other experiments have shown adverse effects on growth of earthworms. There were likely to be risks to sediment-dwelling invertebrates where farmed salmon had been treated with ivermectin to control sea lice. In laboratory tests, freshwater fish appeared to have low sensitivity to ivermectin. In view of the lack of published information about environmental effects of use of avermectins and about endocrine-disrupting chemicals in detergents used in dairy operations, it is recommended that monitoring of dairy discharges for residues of such chemicals should be undertaken.