Does Ivermectin Pollute the Surroundings of Swine Farms?

: Pharmaceuticals are emerging environmental pollutants, with macrocyclic lactones like ivermectin raising concerns due to their widespread use and persistence. This study investigated ivermectin residues in intensive swine farms in Emilia-Romagna, Italy, focusing on treated sows' faeces and environmental samples. Two farms using ivermectin and a control farm without antiparasitic drugs were studied. Faecal, slurry, soil, and wastewater samples were collected at three treatment points: before, and 1 and 10 days post-treatment. Ivermectin was administered either orally or by injection and analysed via liquid chromatography-tandem mass spectrometry. Faecal residues varied significantly with administration route: orally treated sows had higher concentrations in faeces shortly after treatment (median = 930.25 µg kg-1) than injected sows (median = 14.84 µg kg-1). However, 10 days post-treatment, injected sows exhibited higher residue levels in faeces, indicating different excretion patterns. Soil samples fertilised with farm slurry contained ivermectin residues, sometimes exceeding ecotoxicological thresholds for non-target species like dung beetles and earthworms, with the highest concentration reaching 39.23 µg kg-1. No residues above detection limits were found in slurry or wastewater, likely due to ivermectin's hydrophobicity and dilution. The findings underscore the environmental risks of ivermectin use in swine farming and emphasise the need for sustainable drug management. Broader studies are necessary to refine residue distribution patterns and improve environmental guidelines, particularly for other livestock systems and soil types, to ensure ecological sustainability.