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Written by Paul
Dr Paul Manktelow is a vet who’s worked for almost 20 years on the front line in some of the UK’s busiest veterinary hospitals. As Chief Vet in the Charity Sector, he leads a team of vets and nurses that treat thousands of pets every year. Paul also appears regularly in the media as a TV and radio presenter, writer, public speaker and podcast producer.
For decades, parasite prevention has been part of routine pet care.
Monthly flea treatments. Regular worming. Often given automatically, year after year.
But emerging research suggests that some of the chemicals we use to protect our pets may not stay on our pets.
They are turning up in rivers.
How Do Parasite Treatments End Up in Waterways?
Research from UK universities has detected residues of commonly used parasiticides such as fipronil and imidacloprid in rivers and streams. These products are typically applied topically to a pet’s skin. From there, small amounts can transfer:
- Onto hands during stroking
- Into bedding and clothing
- Down household drains during washing
- From bathing or swimming
Wastewater treatment plants are not designed to fully remove these compounds, meaning residues can pass into surface waters.
Studies have detected these chemicals downstream of urban wastewater outlets at concentrations capable of affecting aquatic invertebrates. These tiny organisms form the base of the food chain.
Why Does That Matter?
Flea and tick treatments are designed to kill insects. They do not distinguish between a flea and a water-dwelling invertebrate.
At certain concentrations, exposure can:
- Alter insect behaviour
- Reduce survival
- Disrupt breeding
- Affect wider river ecosystems
When invertebrate populations decline, ripple effects can travel up the food chain.
Does This Mean We Should Stop Treating Parasites?
No!
Parasites can cause genuine disease and suffering. Fleas, lungworm, ticks and intestinal parasites remain important welfare concerns.
The question is not whether parasite treatments are necessary….the question is whether every pet needs them, all of the time?
Many pets live relatively low-risk lifestyles. Others are clearly higher risk.
In the latest episode of The Consult Room, I explore this issue with veterinary surgeon and environmental researcher Andrew Prentis, unpacking the science behind parasite residues and what a more sustainable approach could look like.
🎧 Listen here:
This conversation is not about guilt. It is about understanding the bigger picture and making thoughtful decisions that protect pets and the ecosystems we all depend on.
