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News Article

Potential role of flea products in pesticide contamination of rivers


Veterinary flea products investigated as a potential source of pollution

Researchers at the University of Sussex have found widespread contamination of English rivers with two neurotoxic pesticides commonly used in veterinary flea products: fipronil and the neonicotinoid imidacloprid. The concentrations found often far exceeded accepted safe limits. Their findings are published in Science of the Total Environment.

These chemicals are banned for agricultural use due to the adverse environmental effects, but there is minimal environmental risk assessment for pesticides used on cats and dogs. This is due to the assumption that there are likely to be fewer environmental impacts due to the amount of product used.

However, there is growing concern that this assumption may be incorrect. To investigate dthis, Professor Dave Goulson and Rosemary Perkins from the University of Sussex analysed data gathered by the Environment Agency in English waterways between 2016 and 2018. Fipronil was detected in 98% of freshwater samples, and imidacloprid in 66%.

Rosemary Perkins, a PhD student at Sussex and a qualified vet, said: “The use of pet parasite products has increased over the years, with millions of dogs and cats now being routinely treated multiple times per year.

“Fipronil is one of the most commonly used flea products, and recent studies have shown that it degrades to compounds that are more persistent in the environment, and more toxic to most insects, than fipronil itself. Our results, showing that fipronil and its toxic breakdown products are present in nearly all of the freshwater samples tested, are extremely concerning.”

According to the Veterinary Medicines Directorate (VMD), who funded the research, there are 66 licensed veterinary products containing fipronil in the UK, and 21 containing imidacloprid, either alone or in combination with other parasiticides. These include spot-on solutions, topical sprays and collars impregnated with the active ingredient.

While some of these products can be purchased only with a veterinary prescription, others can be bought without a prescription from pet shops, supermarkets, pharmacies and online. Many pet owners receive year-round preventative flea and/or tick treatment from their veterinary practice via healthcare plans.

Fipronil has a history of very limited agricultural use before its ban in 2017. It is also licensed for use in ant and cockroach baits, however only one product is licensed for use by non-pest-control professionals. Use on pets seems to be a plausible source of the widespread contamination of rivers.

The paper, co-authored with Martin Whitehead from the Chipping Norton Veterinary Hospital and Wayne Civil at the Environment Agency, examines the occurrence of fipronil and imidacloprid in English rivers as indicators of the potential contamination of waterways from the use of pet flea treatments.

They found that the average fipronil concentration across the rivers sampled by the Environment Agency exceeded chronic safety thresholds five-fold. The overall pollution levels in English rivers indicate that fipronil and its toxic breakdown products pose a high risk to aquatic ecosystems.

While, in most rivers, imidacloprid was found to pose a moderate risk, in seven out of the 20 rivers sampled there was a high environmental risk.

The highest levels of pollution were found immediately downstream of wastewater treatment works, supporting the hypothesis that significant quantities of pesticide may be passing from treated pets to the environment via household drains.

Bathing of pets treated with spot-on fipronil flea products has been confirmed as a potentially important route to waterways for fipronil via sewers, and the washing of hands, pet bedding or other surfaces that have come into contact with treated pets are potential additional pathways for entry to sewers. Other pathways for contamination of waterways includes swimming and rainfall wash-off from treated pets. The strong correlation between fipronil and imidacloprid levels across the river sites tested suggest that they may be coming from a common source.

The researchers say their findings suggest the need for a re-evaluation of the environmental risks associated with the use of companion animal parasiticide products, and the risk assessments that these products undergo before regulatory approval.

Article: Perkins, R., Whitehead, M., Civil, W., Goulson, D. (2020). Potential role of veterinary flea products in widespread pesticide contamination of English rivers. Science of the Total Environment (In Press, Corrected Proof), online 7 November 2020, 143560, doi: 10.1016/j.scitotenv.2020.143560

Article details

  • Date
  • 17 November 2020
  • Source
  • University of Sussex
  • Subject(s)
  • Dogs, Cats, and other Companion Animals