Toxicity of ivermectin residues in aged farmyard manure to terrestrial and freshwater invertebrates

Abstract

1. Farmyard manure is often stored, aged and spread on fields as fertiliser; however, dung may be contaminated with residues of veterinary endectocides used to treat livestock for parasites. The persistence of these chemicals during storage and impact on invertebrate biodiversity after spreading are not well understood.2. This study considered whether residues in aged cattle manure could have impacts on terrestrial and freshwater invertebrate biodiversity and ecosystem function.3. Fresh cattle dung was spiked with known concentrations of the endectocide ivermectin or an excipient only (control) and aged in the field for 4 months between February and May 2020. Each month rainwater run-off was collected and used to examine toxicity using the freshwater invertebrate Daphnia magna. In June 2020, manure was spread on mesocosms containing topsoil, and above-ground insect emergence, soil fauna feeding rate, earthworm abundance and pasture productivity (perennial ryegrass growth), were measured over 10 weeks.4. Rainwater-runoff from manure contaminated with ivermectin was highly toxic (60-100% mortality) to D. magna for the entire 4 months of storage. Coleoptera and Diptera emergence was lower from mesocosms spread with ivermectin-contaminated manure compared with control manure. Pasture productivity was significantly lower (18-20%) in mesocosms spread with ivermectin-contaminated manure.5. The results indicate that ivermectin residues aged manure have the potential to retain toxic effects on terrestrial and freshwater invertebrates for at least 4 months of storage, could reduce pasture productivity, and may have pervasive impacts on invertebrate biodiversity in agricultural systems.

Arthrobotrys musiformis (Orbiliales) Kills Haemonchus contortus Infective Larvae (Trichostronylidae) through Its Predatory Activity and Its Fungal Culture Filtrates

“…The most common way to control these parasites has been based on the continuous use of chemical anthelmintic drugs synthesised in the laboratory. These drugs help to reduce the parasitic burden on these animals in some way; however, there are a number of disadvantages associated with their use, i.e., the presence of anthelmintic resistance in the parasites [ 10 , 11 ], the potential contamination of meat or milk or derivates for human consumption [ 12 ] and the contamination of soil and aquifers that can have detrimental environmental effects [ 13 ]. Such negative findings have promoted a poor reputation for their use.…”

BEVA primary care clinical guidelines: Equine parasite control

“…The impacts of veterinary parasiticide residues on beetles, flies and other insects are increasingly recognised and have been the subject of a recent review 332 . The survival, development and reproduction of a range of coprophilic fauna are adversely affected; many, most notably dung beetles, provide functions that are important to soil quality and hence agriculture in addition to being important parts of the ecosystem 333 . Faecal residues or metabolites of drugs belonging to the benzimidazole and levamisole/morantel groups are much less harmful than anthelmintics such as coumaphos, dichlorvos, phenothiazine, piperazine, synthetic pyrethroids and the macrocyclic lactones 334 .…”

Environmental impacts of equine parasiticide treatment: The UK perspective

“…The persistence of anthelmintic drugs during manure storage, and the impact on invertebrate biodiversity after spreading of manure on pastures, is not well understood. Sands and Noll (2022) investigated the persistence of ivermectin residues in aged livestock manure used as a fertiliser on fields, and the impact these residues Although there are a lack of data relating to ivermectin contamination in equine faeces, ivermectin is excreted in the faeces for at least 40 days following oral dosing of horses (Pérez et al, 2001). One study in horses investigating the breakdown of ivermectin during the composting process found an exponential decay of ivermectin at a rate of 1.8% per day with a half-life of 3.6 days (Schwarz & Bonhotal, 2016).…”

“…The persistence of anthelmintic drugs during manure storage, and the impact on invertebrate biodiversity after spreading of manure on pastures, is not well understood. Sands and Noll (2022) investigated the persistence of ivermectin residues in aged livestock manure used as a fertiliser on fields, and the impact these residues may have on terrestrial and freshwater invertebrate biodiversity and ecosystem function. Fresh cattle dung was spiked with known concentrations of ivermectin or an excipient only (control) and aged in the field for 4 months.…”