An Environmental Concern: Uptake of Ivermectin from Growing Substrate to Plant Species

Ivermectin (IVM) is an antiparasitic drug used worldwide. However, its high level of faecal elimination, its transfer to the soil, and the use of manure for soil amendment, represents a potential environmental risk. Two trials were conducted to evaluate the uptake of IVM to: 1) a crop of ryegrass (Lolium multiflorum) and clover (Trifolium repens) growing for 120 days post treatment (dpt) in IVM-spiked soil at 3, 000 (High group, HG) and 90 ng/g (Low group, LG); 2) a crop of radish (Raphanus sativus) and lettuce (Lactuca sativa) growing for 60 dpt in a mix of soil and 10% IVM-spiked manure at 3, 000 ng/g. Soil, soil-manure mix and plants were sampled starting at 15 dpt and at different intervals. IVM concentration (IVMc) was quantified by HPLC. In the HG, IVMc in soil decreased from 2, 154 to 225 ng/g; in ryegrass ranged between 378.65-21.74 ng/g. Strikingly, clover development was delayed; hence, sampling begun 30 dpt. IVMc in clover ranged between 94.09-4.56 ng/g. Significant differences were detected between species (p=0.0374). In the LG, IVMc varied between 22.26-1.02 ng/g in ryegrass and between 10-1.02 ng/g in clover, differences being statistically not significant between species (p=0.8301). IVM was detected in both horticultural species at significant levels (pgreater than0.05) in all sampling times and IVMc was between 10-5 ng/g in radish and 17.70-6.55 ng/g in lettuce. In the substrate IVMc decreased from 1, 311 to 116 ng/g. Consequently, IVM in soil and in composted substrate is transferred to plants during its growth and could be incorporated into the food chain of both livestock and humans.