Deworming products for grazing animals may disrupt food chains

Researchers from Kiel University and Trier University have discovered that the widely used deworming product Cydectin, specifically its active ingredient moxidectin, can disrupt entire networks of ecological relationships when applied to grazing animals. Until now, it was known that deworming agents affect individual species, such as altering seed germination and reducing survival rates of beetle and fly larvae in dung from treated animals. However, this study is the first to examine how these effects play out among multiple species.

The researchers built a simplified food chain model involving three species: cultivated strawberry, green peach aphid, and marmalade hoverfly. The strawberry plant served as food for both insects. Aphids fed on plant sap, while hoverflies used pollen and nectar as adults and preyed on aphids in their larval stage. The study, published in Science of The Total Environment, placed the animals and plants in insect-proof cages, with half of the cages containing soil contaminated with the deworming agent.

The findings revealed that moxidectin significantly impacted the strawberry plants, reducing fruit production by approximately 25%. Aphid populations also increased tenfold without the presence of hoverfly larvae. Hoverflies responded by laying four times as many eggs on treated plants, but these eggs exhibited greater size variability and lower viability, potentially reducing their reproductive success.

Dr. Andrés García, one of the study's authors, expressed surprise at the far-reaching effects of a single product on the interplay between plant and insect. The study highlights the need to consider entire ecological relationships, not just individual species, when assessing the environmental effects of veterinary medicines. Further research is needed to determine the role of moxidectin, other ingredients, and their breakdown products in these effects, as well as their impact on the food chain.

The authors call for greater consideration of complex ecological relationships in future assessments of the environmental impact of veterinary medicines.