Vets should limit the use of flea treatments containing pesticides on dogs and cats, scientists said after a study revealed the large amount of toxic substances in them ending up in rivers.
Pet owners who use this flea treatments risk of contaminating their hands with fipronil and imidacloprid, two insecticides, for at least 28 days after the treatment was applied, according to research by the University of Sussex and Imperial College London.
Dave Goulson, a professor of biology at Sussex who oversaw the research, said: “These two chemicals are extremely potent neurotoxic insecticides and it is extremely worrying that they are regularly found in the hands of dog owners through continuous contact with their pet. Pet owners will also be upset to learn that they are inadvertently polluting our rivers by using these products.”
Veterinarians often recommend regular flea treatments, even when dogs and cats do not have the infestation, to prevent the insects from hiding in their fur. But the scientists say it could have drastic implications for wildlife, as the pesticides contained in the flea treatments could harm fish and invertebrates that live in waterways.
Goulson said: “I would argue that vets should stop encouraging dog and cat owners to use these treatments prophylactically. If an animal doesn’t have fleas, why would you treat it for fleas? Most currently used are simply not needed. Secondly, vets can encourage pet owners to regularly wash the dog or cat bedding – this is where the flea larvae live.”
The insecticides used in the flea products run down household drains when pet owners wash their hands after applying the treatment. Wastewater from sewage treatment plants is a leading source of fipronil and imidacloprid pollution in rivers, with concentrations exceed safe limits for wildlife. Veterinary guidelines recommend that pet owners should not touch their animals until the application site is dry, but the Sussex-Imperial research, published in the journal Science of the Total Environment, shows that contamination lasts for the product’s lifetime.
Fipronil and imidacloprid are widely used in flea treatments, typically applied once a month to the back of the pet’s neck, but are no longer approved for use in landscaping. Imidacloprid belongs to a group of pesticides known as neonicotinoids.
Guy Woodward, a professor of ecology at Imperial College London and co-author of the research, said: “Despite these chemicals being banned from offshore construction use for several years, we still find them in UK freshwaters at levels that can harm aquatic life.. This article shows how household pet flea and tick treatments, a largely overlooked but potentially significant source of contamination, can pollute our waterways.
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Goulson added that the insecticides could be harmful to human health. “More broadly, the environmental impacts of pet parasiticides should be subject to proper risk assessments. Currently they are not, based on a decision made long ago that using pesticides on pets would probably be insignificant in the grand scheme of things. If they are in our hands, these neurotoxins will be everywhere in our homes. That doesn’t sound healthy to me.
“A recent Swiss study found neonicotinoids in the cerebrospinal fluid of 100% of children tested. The health risks associated with long-term human exposure have not been studied.”
