Flea-mergency: Pet treatments taking a bite out of the health of England’s rivers

The delicate balance of life in our rivers is under threat, and it’s not just due to pollution from factories, sewage or agriculture. Surprisingly, one of the culprits is our beloved pets.

Matthew Woodard



The delicate balance of life in our rivers is under threat, and it's not just due to pollution from factories, sewage or agriculture. Surprisingly, one of the culprits is our beloved pets.

In the UK, we now have around 10 million dogs and 11 million cats, with approximately 80% of them receiving regular tick, flea and worm treatments, whether necessary or not.

It's evident that pet owners are keen on keeping their furry companions safe and healthy. However, this well-intentioned approach has unintended consequences because we pet owners are, perhaps unknowingly, polluting our rivers with chemicals that are toxic to aquatic life.

New analysis of Environment Agency data by The Rivers Trust and the Wildlife and Countryside Link, shows that three insecticides used widely in tick, flea and worm treatments (fipronil, permethrin and the controversial neonicotinoid imidacloprid) – are present in English rivers in concentrations that exceed accepted safe limits for wildlife1. This is despite the fact that these chemicals are deemed to be too toxic to be used in agriculture.

In our rivers, insect larvae, such as mayflies and dragonflies, are particularly vulnerable to the toxic effects of these veterinary chemicals. These species and many others serve as essential food sources for fish, birds, and bats. Therefore, when these pesticides enter our rivers, they disrupt the balance of the entire ecosystem, causing ripple effects that impact the wider environment.

This is why The Rivers Trust is amongst 24 environmental and veterinary organisations, including The Progressive Veterinary Association, Veterinary Poisons Information Service, RSPB and The Wildlife Trusts, calling on the UK government to take action and ban all pesticide substances from pet medicines if they are not permitted in agriculture2.

One of the most concerning pesticides found in pet medicines is imidacloprid, which is exceptionally potent, even at tiny concentrations. A single flea treatment of a medium-sized dog with imidacloprid contains enough pesticide to kill 60 million bees3. It's a shocking revelation that should give every pet owner pause.

Despite restrictions on the agricultural use of these pesticides, sales for veterinary use have rocketed, increasing over forty-fold in the case of imidacloprid, between 1997 and 20174.

The reasons for this marked increase are twofold – a rise in the number of pets in the UK and more frequent preventative dosing.

Recent studies indicate that these chemicals are finding their way into rivers from various routes, including contaminated household wastewater from washing treated pets and their clothes and bedding, urinary and faecal excretions, and allowing treated dogs to swim in rivers. The result is a steady flow of harmful pesticides into our rivers, endangering the delicate balance of life within them.

The Rivers Trust believes that we need to close this regulatory loophole urgently. It makes no sense to block these chemicals from being used on crops while allowing them to be routinely applied by millions of pet owners every month.

Where safer alternatives exist, chemicals that harm wildlife should be removed from the market. We must consider efficacy, as well as environmental risks, when authorising veterinary medicines. We also suggest considering new regulations, such as requiring prescriptions for these treatments and assessing their environmental impact before they are approved for use.

We owe it to our pets, rivers, and the fragile ecosystems that depend on them to act responsibly and stop inadvertently poisoning our rivers.

Chemical-free alternatives for treating and preventing fleas on pets

  1. Regular Grooming: Regular grooming is one of the most effective chemical-free methods for controlling fleas. Brush your pet's fur frequently to remove flea eggs or larvae and use a fine-toothed comb to catch adult fleas. A clean coat is less attractive to fleas.
  2. Bathing with Herbal Shampoos: Choose a natural, herbal pet shampoo that contains ingredients like neem oil, lavender, or rosemary. These ingredients have natural flea-repelling properties and can help deter fleas while keeping your pet clean and fresh.
  3. Flea-Repellent Collars: Look for flea collars that use natural ingredients like essential oils (e.g., cedarwood or eucalyptus) to repel fleas. These collars are a safe and chemical-free option for keeping fleas at bay.

When using these chemical-free alternatives, it's essential to consult with your veterinarian, especially if your pet has pre-existing health conditions, is very young, or is pregnant. Additionally, remember that consistency is key, and you may need to combine multiple methods for effective flea prevention. Regularly clean and vacuum your home to remove flea eggs or larvae and wash your pet's bedding in hot water to help prevent infestations.


1A call for toxic pesticides in pet medicines to be banned - Pesticide Action Network UK (pan-uk.org)

2PAN open letter to Government

3Pet Flea Treatments Poisoning Rivers

4To flea or not to flea: survey of UK companion animal ectoparasiticide usage and activities affecting pathways to the environment

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