Environmental consequences of treating cattle with the antiparasitic drug ivermectin

Abstract

Ivermectin (22,23-dihydroavermectin B1) is a recently discovered, persistent, broad-spectrum, antiparasitic drug of unpredecented potency which is now routinely administered to cattle, horses, sheep and pigs in many countries. In cattle, it is an efficient control for parasitic gastrointestinal and respiratory tract nematodes, warble fly, mites, lice and ticks. However, most of the ivermectin dose is ultimately eliminated in the faeces of the treated animals where it has been shown to have an insecticidal effect on the larvae of economically important, dung-breeding, haematophagous Diptera. Nevertheless, the effects of excreted ivermectin on the cowpat fauna as a whole and the wider consequences of such effects have not previously been considered. In field trials reported here, the faeces of calves fitted with rumenal boluses delivering ivermectin at 40 micrograms per kg per day, failed to degrade in the normal way and this failure was associated with the absence of dung-degrading insects. Faeces from placebo-treated controls contained a characteristic dung-degrading invertebrate community and were largely degraded within 100 days. These results indicate that the increasing widespread use of ivermectin may have important environmental consequences for pastureland.

The negative effects of the residues of ivermectin in cattle dung using a sustained-release bolus on Aphodius constans (Duft.) (Coleoptera: Aphodiidae)

“…Wall and Strong [21] first drew attention to the powerful insecticidal effect of avermectins on non-target species of the dungbreeding community. Ivermectin residues in cattle dung particularly affect Cyclorrhaphan Diptera [20].…”

“…This suggests that the faecal excretion of high ivermectin concentrations for prolonged periods after bolus administration to cattle may represent a threat to the ecosystem, as a reduction of insect activity was associated with slower dung pat degradation [5,11,21,22]. and the editor is gratefully acknowledged.…”

“…Ivermectin has a high potency at low concentrations against nematodes and arthropods, in particular against dung beetles and flies [8,18,20,21], and it has been demonstrated that dung pats containing ivermectin are degraded significantly slower than pats containing no ivermectin [3,13,20,21]. Although some authors [3,15] have previously recommended that cattle breeders treat their cattle with subcutaneous injection of ivermectin when there is negligible dung beetle activity, the spread of the use of Résumé -Effets négatifs des résidus d'ivermectine délivrés par un bolus à diffusion lente sur la survie du coprophage Aphodius constans (Duft.)…”

Treatment of reindeer with ivermectin - effect on dung insect fauna

“…Most of the dose given to an animal is excreted unaltered in the faeces (Halley et al, 1989). Studies on cattle show that ivermectin residues in faeces may have a negative effect on the dung fauna (Wall & Strong, 1987;Fincher, 1992;Strong, 1992Strong, , 1993Gunn & Sadd, 1994), and the wide use of ivermectin in reindeer (Rangifer tarandus) has given rise to a concern among reindeer herders, veterinarians, environmental authorities as well as the general public, on possible negative ecological effects on reindeer grazing areas, as reflected especially in Norwegian newspapers (Berg, 1991;Tonstad, 1991;Anonymous, 1992).…”

Peer Reviewed: Are Veterinary Medicines Causing Environmental Risks?

“…Although the impacts of selected compoundsmost notably anthelmintics and selected antibacterial compounds have been extensively investigated (3,4), many other substances found in the environment are less publicly well understood. As a result, researchers have raised questions about the impact of veterinary medicines on organisms in the environment and on human health.…”