Veterinarians should stop “profiteering” by prescribing preventive flea treatments for dogs and cats that harm insects and songbirds, a leading scientist has warned.

In the UK, it is common practice to recommend preventive flea treatments every few months, even for pets without fleas. However, these treatments contain powerful insecticides that can leach off pet fur and their owners’ hands into waterways.

Recent research revealed that songbirds are unintentionally poisoning their young by using contaminated pet fur in their nests.

Concerns are growing over the environmental impact of these chemicals. Insecticides like imidacloprid and fipronil are particularly harmful. Just one monthly flea dose for a large dog has enough imidacloprid to kill 25 million bees.

Dave Goulson, professor of biology at the University of Sussex, where the songbird study was carried out, said: “Given the scale of environmental contamination it is causing, prophylactic use of flea treatments on family pets cannot continue.

“Defra [Department for Environment, Food and Rural Affairs] and the veterinary profession need to take responsibility for development of a sustainable alternative, but an obvious first step is to stop treating animals for fleas if they don’t have fleas.

“After all, we don’t treat our children against nits if they don’t have them. Promoting prophylactic, monthly treatment is simply profiteering.”

While the UK government is considering a ban on imidacloprid in agriculture, no such restrictions are planned for pet products.

Flea prevention can also be managed by regularly using a flea comb and washing pet bedding.

“I’ve felt really pushed, and a bit patronised, by our vets for not subscribing to their monthly programme to receive monthly flea and worm treatment (and vaccines),” said Helen Hedges, a nurse who has two dogs.

“I’ve moved to an independent vet who are better and more open to discussing alternative options. Why do I need to apply chemicals to them if they don’t actually have fleas?! I never did this to my children – I only treated them for nits when they had nits, not monthly to prevent them.

“Even this has its downfalls though as vets can’t prescribe flea treatment if they haven’t seen a dog for six months, so the only time my dogs had fleas in the last two years cost nearly £200 for the consultation and treatment for both dogs.”

The British Veterinary Association (BVA) urges further research on these pesticides’ environmental effects and advises vets to use them responsibly.

The BVA president, Elizabeth Mullineaux, said: “Parasiticides play an important role in preventing and treating parasites in animals, which if left unaddressed can lead to bigger health and welfare issues in both animals and people.

“Rather than blanket use, we strongly encourage vets and owners to take a risk-based approach to prescribing or recommending these medicines, reflecting an animal’s exposure to parasites.

“Owners should speak with their vet about their animal’s needs and how to responsibly use and dispose of these medicines to minimise environmental contamination.”