Sorption of selected antiparasitics in soils and sediments

From soil sorption to bioaccumulation: Tracing the endectocide ivermectin in soil and earthworms

Ivermectin (IVM), a widely used antiparasitic drug in veterinary medicine, has emerged as an environmental contaminant due to its semi-persistence and potentially harmful ecotoxicological impacts on non-target terrestrial fauna. This study investigates the innovative combination of sorption, desorption, and bioaccumulation dynamics of IVM in soil-earthworm systems, focusing on the species Eisenia fetida, Aporrectodea caliginosa, and Lumbricus terrestris. Sorption experiments in artificial soil (AS) and its components (sand, clay, peat) revealed a strong affinity of IVM for organic-rich substrates, reducing bioavailability and bioaccumulation. Bioaccumulation studies showed that the kinetic bioaccumulation factor BAFk for IVM in E. fetida ranged from 0.505 to 0.727 g soil dw/g earthworm dw, with elimination kinetics best described by a biphasic model, and suggesting minimal net accumulation. A. caliginosa and L. terrestris showed slightly higher accumulation potential, with accumulation factors exceeding 1 during the uptake phase, although equilibrium was not reached within 21 days. The prolonged accumulation process, combined with a calculated DT50 of 142 days in AS, underscores IVM's potential environmental persistence and risk, particularly its ecotoxicological relevance. The results also suggest that strong sorption to organic matter in soils can mitigate bioaccumulation.

Competition moderates impact of anthelmintic-contaminated soil on growth and fitness of temperate grassland species

In animal husbandry, the macrocyclic lactone anthelmintic moxidectin is commonly used and may accumulate in pasture soils, potentially impacting plant growth and fitness. To investigate these effects while considering plant competition, we conducted a completely randomised pot experiment. We grew four temperate grassland species - Achillea ptarmica, Agrostis capillaris, Dianthus deltoides, and Plantago lanceolata - separately in pots, with soil treated with formulated moxidectin at three concentration levels (0.1, 1, 5 μg g-1) or left untreated (control). In half of the pots, we added the dominant grass species Poa pratensis as a competitor. Over a full growth period in a greenhouse, we measured three morphological traits: above-ground plant biomass (APB), specific leaf area (SLA), and intact leaf area (ILA). Moxidectin concentrations in the above-ground plant parts and soil were analysed using HPLC. Results showed that moxidectin was absorbed by the roots and transported to the above-ground plant parts. At the highest concentration (5 μg g-1), APB and ILA were reduced by 14.4 % and 19.8 %, respectively, compared to controls, while SLA increased by 12.2 %. Anthelmintic effects varied with competition; for APB, significant effects were noted only in the absence of competition for three out of four species. The highest increases in SLA and reductions in ILA at 5 μg g-1 occurred without competition in one and three species, respectively. These findings suggest that soil contamination by anthelmintic residues can negatively affect the growth and fitness of grassland plants, particularly in low-competition areas, such as open soil patches, which serve as protective microsites for plant recruitment.

Anthelmintics in the environment: Their occurrence, fate, and toxicity to non-target organisms

Anthelmintics are drugs used for the treatment and prevention of diseases caused by parasitic worms (helminths). While the importance of anthelmintics in human as well as in veterinary medicine is evident, they represent emerging contaminants of the environment. Human anthelmintics are mainly used in tropical and sub-tropical regions, while veterinary anthelmintics have become frequently-occurring environmental pollutants worldwide due to intensive agri- and aquaculture production. In the environment, anthelmintics are distributed in water and soil in relation to their structure and physicochemical properties. Consequently, they enter various organisms directly (e.g. plants, soil invertebrates, water animals) or indirectly through food-chain. Several anthelmintics elicit toxic effects in non-target species. Although new information has been made available, anthelmintics in ecosystems should be more thoroughly investigated to obtain complex knowledge on their impact in various environments. This review summarizes available information about the occurrence, behavior, and toxic effect of anthelmintics in environment. Several reasons why anthelmintics are dangerous contaminants are highlighted along with options to reduce contamination. Negative effects are also outlined.

A comprehensive study on the ecotoxicity of ivermectin to earthworms (Eisenia fetida)

Ivermectin (IVM) is a dewormer commonly utilized in animal farming. Nevertheless, there is a deficiency of research on the bioecotoxicity of IVM in soil. In this study, earthworms were utilized as test animals to investigate the ecotoxicological impacts of IVM. The experiment lasted 28 days and involved adding varied doses of IVM to a culture substrate of soil mixed with cow dung and feeding it to earthworms. The experiment entailed recording earthworm weight, number of earthworm cocoons, histological damage, oxidative stress indicators, and gene expression levels. The analysis results showed that earthworm growth and reproduction were hampered by IVM. Moreover, pathological damage to the earthworms increased with increasing IVM concentration, which caused increased oxidative damage to the earthworms. These findings offer a summary of the impact of IVM on earthworms and a reference point for future research examining the ecological implications of IVM.

A review on the ecotoxicity of macrocyclic lactones and benzimidazoles on aquatic organisms

Despite its wide production and several applications, veterinary antiparasitics from macrocyclic lactones and benzimidazole classes have not received much scientific attention concerning their environmental risks. Thus, we aimed to provide insights into the state of the environmental research on macrocyclic lactone and benzimidazole parasiticides, emphasizing their toxicity to non-target aquatic organisms. We searched for relevant information on these pharmaceutical classes on PubMed and Web of Science. Our search yielded a total of 45 research articles. Most articles corresponded to toxicity testing (n = 29), followed by environmental fate (n = 14) and other issues (n = 2) of selected parasiticides. Macrocyclic lactones were the most studied chemical group (65% of studies). Studies were conducted mainly with invertebrate taxa (70%), with crustaceans being the most predominant group (n = 27; 51%). Daphnia magna was the most used species (n = 8; 15%). Besides, it also proved to be the most sensitive organism, yielding the lowest toxicity measure (EC₅₀ 0.25 μg/L for decreased mobility after 48 h-abamectin exposure) reported. Moreover, most studies were performed in laboratory settings, tracking a limited number of endpoints (acute mortality, immobility, and community disturbance). We posit that macrocyclic lactones and benzimidazoles warrant coordinated action to understand their environmental risks.

Biodegradation of anthelmintics in soils: does prior exposure of soils to anthelmintics accelerate their dissipation?

Anthelmintics (AHs) control animal infections with gastrointestinal nematodes. They reach soil through animal faeces deposited on soils or through manuring. Although soil constitutes a major AH sink, we know little about the mechanisms controlling their soil dissipation. We employed studies with fumigated and non-fumigated soils collected from 12 sheep farms with a variable record of albendazole (ABZ), ivermectin (IVM) and eprinomectin (EPM) use. From each farm, we collected soils from inside small ruminant barn facilities (series A, high exposure) and the associated grazing pastures (series B, low exposure). We asked the following questions: (a) What is the role of soil microorganisms in AH dissipation? (b) Does repeated exposure of soils to AHs lead to their accelerated biodegradation? (c) Which soil physicochemical properties control AH dissipation? Soil fumigation significantly retarded ABZ (DT₅₀ 1.9 and 4.33 days), IVM (34.5 and 108.7 days) and EPM dissipation (30 and 121 days) suggesting a key role of soil microorganisms in AH dissipation. No significant acceleration in AH dissipation was evident in soils from units with a record of the administration of AHs or in soil series A vs series B, suggesting that the level of prior exposure was not adequate to induce their enhanced biodegradation. Significant positive and negative correlations of soil total organic carbon (TOC) and ABZ and IVM dissipation, respectively, were observed. Soil adsorption of AHs increased in the order IVM > ABZ > EPM. TOC controlled soil adsorption of IVM and EPM, but not of ABZ, in support of the contrasting effect of TOC on IVM and ABZ dissipation.