Pet Ectoparasiticides: A multidisciplinary investigation into environmental, ani

Pet Ectoparasiticides: A multidisciplinary investigation into environmental, animal and public health and deep dive into use practices. Purpose and Rationale Recent research into the environmental impact of topical flea and tick treatments has focused on environmental monitoring and potential exposure pathways. Perkins and Goulson (2023) analysed Environment Agency (EA) monitoring data from 2016 to 2018 and found that fipronil exceeded chronic toxicity thresholds for aquatic invertebrates at 80% of sites, while imidacloprid exceeded these limits at 35% of sites. They also observed higher concentrations of both substances near wastewater treatment works, suggesting domestic use as a likely source. More recent discussions with the EA indicate that concentrations have remained relatively stable since 2018. Subsequent studies have identified key exposure routes for spot-on treatments, including down-the-drain emissions and dog swimming (Perkins et al., 2024; Yoder et al., 2024; Perkins et al., 2025). Additionally, fipronil and imidacloprid have recently been detected in the nests of songbirds, raising further concerns about environmental contamination (Tassin de Montaigu et al., 2025). While veterinary medicines may not be the sole source, this body of research suggests they are contributing to detectable levels of these substances in aquatic environments and potentially the wider ecosystem.