Parasiticides in the Environment

The primary focus of VetSalus has always been on the production of ‘healthy food from healthy animals’. The range of educational material provided by the business and its international network of veterinary consultants has been firmly focused on the production of food from farm animals. However, VetSalus has a broad, One Health interest and, as well as highlighting farm productivity matters, it has also commented on many other issues including sustainability and animal welfare. For example, articles and educational initiatives have frequently told the story of dung beetles and have advised the use of integrated parasite management practices to reduce their usage and environmental impact.

Just occasionally, the VetSalus educational brief can stretch beyond food production and the growing recognition of the threat posed to the environment by parasiticides used primarily on companion animals, provides an opportunity to extend our normal perspective a little. 

Concern has been growing in recent years about the levels of the commonly used pet flea and tick treatments which are detectable in the environment. The work of Perkins et al [1] who studied English rivers in 2021, showed levels of fipronil compounds (fiproles) and imidacloprid exceeding toxic levels by significant margins, in a high percentage of samples. The authors conclude that the presence of these compounds is widespread in U.K. rivers, that they are likely to present a significant threat to the environment and that veterinary flea treatments are the most likely source, possibly via contamination from sewerage. 

In July 2025, the U.K. government announced a project to increase understanding of the potential threat but any legislation to control the risks appears to be some distance away [2]. The British Veterinary Association has also been developing policies which advise its members against blanket treatments [3]. However a wide range of flea and tick products containing fipronil and imidacloprid are readily available via the internet purchase, well beyond veterinary control.

One initiative which will prove to be of value to veterinary clinicians and their clients has been recently launched by Vet Sustain [4]. The ‘not for profit’ organisation launched a major new resource in September 2025 which provides downloadable risk assessment tools for use in both cats and dogs [5]. Their new guide is intended to support responsible prescribing of parasiticides for small animals and is based on the “4 R’s” [6]:

• REVIEW your current approach to parasiticide prescription

• REPLACE indiscriminate prophylactic prescribing with an individualised risk assessed approach

• REDUCE environmental exposure to parasiticides whilst preserving animal health and welfare by reducing unnecessary treatments where exposure to parasites or patent infections are not suspected or likely.

• REFINE the use of pet parasiticides where they have been deemed necessary by ensuring the responsible and informed selection and administration of products.

Historically, products used on companion animals have been assumed to be more remotely connected to both the food chains and the environment and thus present a lower risk profile. It is becoming clearer that this is not necessarily so and VetSalus welcomes these recent initiatives which further underline the important roles that veterinarians play in One Health.