The avermectins, milbemycins and spinosyns are collectively referred to as macrocyclic lactones (MLs) which comprise several classes of chemicals derived from cultures of soil micro-organisms. These compounds are extensively and increasingly used in veterinary medicine and agriculture. Due to their potential effects on non-target organisms, large amounts of information on their impact in the environment has been compiled in recent years, mainly caused by legal requirements related to their marketing authorization or registration. The main objective of this paper is to critically review the present knowledge about the acute and chronic ecotoxicological effects of MLs on organisms, mainly invertebrates, in the terrestrial and aquatic environment. Detailed information is presented on the mode-of-action as well as the ecotoxicity of the most important compounds representing the three groups of MLs. This information, based on more than 360 references, is mainly provided in nine tables, presenting the effects of abamectin, ivermectin, eprinomectin, doramectin, emamectin, moxidectin, and spinosad on individual species of terrestrial and aquatic invertebrates as well as plants and algae. Since dung dwelling organisms are particularly important non-targets, as they are exposed via dung from treated animals over their whole life-cycle, the information on the effects of MLs on dung communities is compiled in an additional table. The results of this review clearly demonstrate that regarding environmental impacts many macrocyclic lactones are substances of high concern particularly with larval instars of invertebrates. Recent studies have also shown that susceptibility varies with life cycle stage and impacts can be mitigated by using MLs when these stages are not present. However information on the environmental impact of the MLs is scattered across a wide range of specialised scientific journals with research focusing mainly on ivermectin and to a lesser extent on abamectin doramectin and moxidectin. By comparison, information on compounds such as eprinomectin, emamectin and selamectin is still relatively scarce.

Residues of veterinary parasiticides in dung of treated livestock have nontarget effects on dung-breeding insects and dung degradation. Here, we review the nature and extent of these effects, examine the potential risks associated with different classes of chemicals, and describe how greater awareness of these nontarget effects has resulted in regulatory changes in the registration of veterinary products.

A single injection of calves with ivermectin, at the recommended anthelmintic dose rate of 200 μg/kg of body weight, was effective in killing the larvae of the dung‐breeding dipteran, Orthelia cornicina for up to 32 days post‐treatment. Newly emerged beetles of the scarabaeine dung beetle, Copris hispanus, suffered 90 % mortality in dung dropped on days two and three after injection and 27.5 % mortality in dung of day 16. Feeding activity was greatly suppressed in dung of days 1–8, but was normal in dung of days 32 and 64, in which there was no substantial mortality. In the 1–16 day treatments, survivors showed aberrant reproductive development. When ovipositing C. hispanus were fed with day 3 dung, there was no adult mortality but oviposition rate was reduced and immature survival was zero. No mortality occurred among sexually mature adults of the dung beetle, Bubas bubalus when fed for five weeks on dung collected at intervals ranging from 1–32 days after injection. Substantial mortality was recorded among newly emerged beetles of Onitis belial, following exposure to ivermectin residues. Environmental implications of these results are discussed. Zusammenfassung Über die Wirkungen der antiparasitischen Droge Ivermectin auf Entwicklung und Überleben der Dungfliege Orthelia cornicina (F.) sowie der Dungkäfer Copris hispanus L., Bubas bubalus (Ol.) und Onitis belial F. Eine Einzelinjektion bei Kälbern mit Ivermectin in der empfohlenen Dosis von 200 μg/kg Körpergewicht tötete die Entwicklungsstadien der Dungfliege O. cornicina bis zum 32. Tag nach Behandlung. Frisch geschlüpfte Käfer von C. hispanus erlitten in 2 und 3 Tage nach der Injektion produziertem Dung 90 % Sterblichkeit, in Dung vom 16. Tag 27,5 %. Die Fraßaktivität der Käfer war in Dung vom 1.‐8. Tag stark gehemmt, jedoch in Dung vom 32. und 64. Tag normal, wo keine deutliche Sterblichkeit mehr bestand. In Dung vom 1. bis 16. Tag nach Behandlung zeigten überlebende Käfer aberrante Reproduktion. Wurden Eier ablegende C. hispanus mit Dung vom 3. Tage gefüttert, zeigte sich keine Adulten‐Mortalität, doch war die Eiablage‐Rate verringert und die Entwicklung von Nachkommen gleich 0. Dagegen wurde keine Mortalität unter den geschlechtsreifen Adulten des Dungkäfers B. bubalus beobachtet, wenn diese 5 Wochen lang von Dung fraßen, der zwischen dem 1. und 32. Tag nach der Injektion produziert worden war. Teilmortalität wurde unter frisch geschlüpften Käfern von O. belial beobachtet als Folge der Kontaminierung mit Ivermectin‐Rückständen. Die Umweltzusammenhänge mit diesen Ergebnissen werden erörtert.

Data from dung-baited pitfall traps show that dung beetles (Coleoptera: Scarabaeidae) do not discriminate against dung from sheep or cattle treated with avermectin. On the contrary, for a period post-treatment, dung from animals treated with avermectin attracted more beetles than dung from untreated animals. This effect was more marked with cattle dung than with sheep dung. The period of enhanced attractiveness of sheep dung was restricted to dung produced during the first day after treatment, whereas with cattle dung, the effect was still evident in faeces produced 25 days after treatment. Cattle dung produced from 3-25 days post-treatment caused 100% mortality in newly hatched larvae of the bushfly, Musca vetustissima Walker (Diptera:Muscidae). In dung of day 35, mortality was 93.6%. Dung collected from sheep from 1-6 days after treatment also caused 100% mortality of fly larvae, but by day 28, no toxic effects were detectable. Field observations on the colonization of cattle pats confirmed the enhanced attractiveness of dung from treated animals and suggested that departure rates from treated dung were lower than those from untreated dung. Treated pats supported higher beetle populations than untreated pats and burial was more rapid. The potentially serious implications of the enhanced attractiveness of avermectincontaminated dung are discussed in relation to the survival of dung beetle communities.