New Forest Dog On The Forest Off The Lead

Some flea treatments harm New Forest water wild life

A new study exploring the potential impact of powerful insecticides used in some popular flea treatments for dogs has provided the first evidence for potential harm to New Forest waterbodies and their aquatic fauna.

The study discovered that one of the commonest insecticides used in ‘spot-on’ flea treatments, a chemical called imidacloprid, was detected at four locations where dogs are known to regularly enter the water. At one of these sites, Dibden Bottom, the levels of imidacloprid were nearly double the internationally agreed toxicity threshold for aquatic invertebrates.

Previous studies have shown that prolonged exposure to these chemicals can negatively impact insect species, including dragonfly, damselfly, and mayfly larvae, which are important components of the aquatic ecosystem and provide food for fish, birds, and bats. Imidacloprid has been banned as an agricultural insecticide due to concerns over the impact on pollinating insects, for example, Prof Dave Goulson at University of Sussex has estimated that one flea treatment of a medium-sized dog with imidacloprid contains enough pesticide to kill 60 million bees.

The survey work was conducted by Wild New Forest and Freshwater Habitats Trust. Prof Russell Wynn of Wild New Forest says: “Although there is growing awareness of the pervasive nature of these chemicals in English rivers, we suspect that most dog-walkers will be unaware of the potential impacts of allowing their dog to enter the water here in the New Forest. We hope that by collecting and openly sharing these data we can raise awareness amongst the community and start a positive discussion about less harmful alternatives”.

Dr Naomi Ewald of Freshwater Habitats Trust says: “The New Forest is an Important Freshwater Landscape, where the ponds and small headwater streams support some of the most diverse plant and animal communities to be found in the UK. These habitats also support our rarest freshwater species, which have disappeared from large swathes of the wider countryside. Keeping New Forest freshwaters clean and free from polluting agricultural nutrients and urban chemicals is a priority if these species are to survive and thrive.

The survey team are working with New Forest Dog Owners Group (NFDOG) and other New Forest partners to help raise awareness of this issue and provide the local community with information about alternative treatments that are less likely to cause harm; they will also be contacting local vets in and around the New Forest to alert them to these new findings. 

Heather Gould, Chairman of NFDOG says: “It’s essential that we protect our environment. These findings, which are in line with other studies in the UK, are important. It’s also important though, that dog owners protect their pets. Vets are aware of the issue, and owners should discuss this before selecting which treatment to use. The same applies in pet stores if owners buy their treatment there. Further information about the alternatives is on our website.”

The first phase of water sampling was conducted in late October 2023 supported by a grant from Friends of the New Forest. The survey team intend to conduct another round of sampling in summer 2024, at a time of lower water levels and higher recreational activity.

The campaign group Pesticides Action Network list safer alterative treatments, derived from the Veterinary Medicines Directorate approved drug list. You can find their list of more than 270 alternatives here:  Please note that NFDOG is not responsible for this list. 

This story has been written jointly by Wild New Forest, NFDOG, and other partners.