Ivermectin and Soil Health - The Basics
AUTHOR: Lahra Harcourt-Brown
BSc(Hons) BVM&S MRCVS
The complexity of soil organisms
Soil is composed of a complex community of organisms that support its physical, chemical, and biological functions. Within the soil, organisms are continuously cycling nutrients, with each serving a different and vital role in this interlinked food web.
A functioning soil ecosystem is crucial for promoting nutrient cycling, maintaining good soil structure, and ensuring sufficient nutrients are available to plants and subsequent crop yields. Livestock have the potential to aid in improving this soil health, by contributing organic matter to the soil to be utilised as an energy source.
Livestock dung and the soil ecosystem
Livestock manure is utilised in many crop and livestock systems to add organic matter to soils, improving productivity and carbon stores. Whether it is incorporated from individual dung pats in grazing systems or spread as manure or slurry in arable or silage rotations, dung is decomposed and utilised by soil organisms to add organic matter and essential nutrients and maintain soil quality.
How does Ivermectin end up in the soil, and why is this a concern?
There is little metabolism of Ivermectin following treatment, leading to excretion of a relatively unchanged chemical. The residue of Ivermectin might remain in farmyard manure and slurry for up to four months, if not longer.
Manure contaminated with parasiticides poses a greater risk to soil organism function and health. Following excretion, organisms involved in dung decomposition are at risk of the toxic effects, along with those, such as earthworms, which may absorb the Ivermectin residues once it has entered the soil. Pathways that rely on these organisms will therefore be affected by their loss.
Unfortunately, the consensus of the research is that there are also likely to be far more harmful impacts than we are currently unaware of. Pursuing approaches to reduce Ivermectin use on farms is paramount to avoid increasing the residue effects on the soil and harmful downstream effects.
Further reading:
Ashman, M.R. and Puri, G. (2002) ‘Chapter 4’, in ‘Essential soil science: A clear and concise introduction to soil science.’ Oxford: Blackwell Science, pp. 67–88.
Bricarello, P. A., Longo, C., da Rocha, R. A., & Hötzel, M. J. (2023) Understanding Animal-Plant-Parasite Interactions to Improve the Management of Gastrointestinal Nematodes in Grazing Ruminants. In Pathogens (Vol. 12, Issue 4). MDPI. https://doi.org/10.3390/pathogens12040531
de Souza, R. B., & Guimarães, J. R. (2022) ‘Effects of Avermectins on the Environment Based on Its Toxicity to Plants and Soil Invertebrates-a Review.’ Water, air, and soil pollution, 233(7), 259. https://doi.org/10.1007/s11270-022-05744-0
Floate, K.D., Wardhaugh, K.G., Boxall, A.B.A., Sherratt, T.N., (2005) ‘Fecal residues of veterinary parasiticides: Nontarget effects in the pasture environment’, Annual Review of Entomology, 50(1), pp. 153–179. doi:10.1146/annurev.ento.50.071803.130341.
Jensen, J., & Scott-Fordsmand, J. J. (2012) ‘Ecotoxicity of the veterinary pharmaceutical ivermectin tested in a soil multi-species (SMS) system.’ Environmental Pollution, 171, 133–139. https://doi.org/10.1016/j.envpol.2012.07.014
Iglesias, L. E., Saumell, C., Sagüés, F., Sallovitz, J. M., & Lifschitz, A. L. (2018) ‘Ivermectin dissipation and movement from feces to soil under field conditions.’ Journal of Environmental Science and Health – Part B Pesticides, Food Contaminants, and Agricultural Wastes, 53(1), 42–48. https://doi.org/10.1080/03601234.2017.1371554
Lupwayi, N. Z., Floate, K. D., Schwinghamer, T. D., Hao, X., & Kanashiro, D. A. (2023) ‘Trickle-down effects of the cattle parasiticide ivermectin on soil microfauna on a prairie grassland.’ Applied Soil Ecology, 190. https://doi.org/10.1016/j.apsoil.2023.105021
Sands, B. and Noll, M. (2021) ‘Toxicity of ivermectin residues in aged farmyard manure to terrestrial and freshwater invertebrates’, Insect Conservation and Diversity, 15(1), pp. 9–18. doi:10.1111/icad.12526.
