Fate and effects of ivermectin on soil invertebrates in terrestrial model ecosystems

Abstract

The effect of ivermectin on soil organisms was assessed in Terrestrial Model Ecosystems (TMEs). Intact soil cores were extracted from a pasture in England and kept for up to 14 weeks in the laboratory. Ivermectin was applied to the soil surface via spiked cow dung slurry at seven concentration rates ranging from 0.25 to 180 mg/TME, referring to concentrations of 0.19-227 mg ivermectin/kg soil dry weight in the uppermost (0-1 cm) soil layer. After 7, 28 and 96 days following the application soil cores were destructively sampled to determine ivermectin residues in soil and to assess possible effects on microbial biomass, nematodes, enchytraeids, earthworms, micro-arthropods, and bait-lamina feeding activity. No significant effect of ivermectin was found for microbial respiration and numbers of nematodes and mites. Due to a lack of dose-response patterns no effect concentrations could be determined for the endpoints enchytraeid and collembolan numbers as well as total earthworm biomass. In contrast, EC50 values for the endpoint feeding rate could be calculated as 0.46, 4.31 and 15.1 mg ivermectin/kg soil dry weight in three soil layers (0-1, 0-5 and 0-8 cm, respectively). The multivariate Principal Response Curve (PRC) was used to calculate the NOEC(community), based on earthworm, enchytraeid and collembolan abundance data, as 0.33 and 0.78 mg ivermectin/kg soil dw for day 7 and day 96, respectively. The results shown here are in line with laboratory data, indicating in general low to moderate effects of ivermectin on soil organisms. As shown by the results of the bait-lamina tests, semi-field methods such as TMEs are useful extensions of the battery of potential test methods since complex and ecologically relevant endpoints can be included.

Nontarget effects of ivermectin residues on earthworms and springtails dwelling beneath dung of treated cattle in four countries

“…The multivariate principal response curve was used to calculate the NOEC community , based on earthworm, enchytraeid, and springtail abundance data, as 0.33 mg ivermectin/kg dry weight soil and 0.78 mg ivermectin/kg dry weight soil for day 7 and day 96 of the present study, respectively. Because these ivermectin concentrations are at least 10‐fold higher than the actual values measured in the present study, the results of Förster et al support the conclusion that ivermectin in field‐relevant concentrations does not severely affect springtails under field conditions.…”

Environmental risk assessment of ivermectin: A case study

“…According to VICH (2004), no further fate studies are required for ivermectin in phase II tier B. However, as part of a semifield study using terrestrial model ecosystems (TMEs), some information on the actual concentrations of ivermectin in soil cores were collected (Förster et al 2010). The TMEs were designed and performed as described by Knacker et al (2004).…”

Effects of ivermectin application on the diversity and function of dung and soil fauna: Regulatory and scientific background information

“…For the dung beetle Aphodius constans, EC50 values of 100 mg/kg dung fresh weight [36] and 176 mg/kg dung fresh weight [37] have been reported. Staphylinid beetles did react less sensitively to ivermectin than "true" dung flies and beetles, both in terrestrial model ecosystems [38] and in the field [39]. However, parasitoids of dung organisms such as wasps are consistently among the most sensitive organisms studied [6].…”