Don’t treat your pets for parasites such as ticks and fleas unless they actually need treating. We can’t be sure that these treatments are safe for you and your family, and there is growing evidence that they pose a danger to wildlife.
So says a report by the Environment and Climate Change Committee of the UK’s House of Lords. It is calling for the sale of these treatments to be restricted, so people can only buy them after consultation with a vet, pharmacist or qualified pet shop staff.
The main issue is that there is no rigorous assessment of pet treatments before they are approved, the report says. It’s simply been assumed by national and international regulators that they are safe, but this assumption is turning out to be wrong.
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In particular, at least two potent pesticides found in tick and flea treatments are getting into UK rivers at levels high enough to affect wildlife. These pesticides can break down into other substances that are even more harmful.
“There is also worryingly insufficient evidence to assess whether or not [pet parasite medicines] are harmful to human health,” says the report.
It also says regulators are not sufficiently independent. Both UK and international regulators “appear to be too influenced by and beholden to the views of the industry”, it states.
While the report focuses on the UK, the same tick and flea treatments are sold in many countries. “This is a worldwide issue,” says Rosemary Perkins at Imperial College London, one of the experts who gave evidence to the committee.
“There’s been a historical assumption that any veterinary medicine used in non-food animals – cats and dogs, companion animals – is associated with negligible environmental risk,” she says. “Effectively, they have no meaningful environmental risk assessment.”
But recent research shows they do pose a risk, says Perkins. “It’s really opened up a Pandora’s box, because we have dozens of these products that have been approved based on this assumption that we now know is not scientifically valid.”
For instance, two common pesticides found in products such as spot-on flea treatments are fipronil, a broad-spectrum insecticide, and imidacloprid, a neonicotinoid. “They’re incredibly potent at extremely low levels,” says Perkins.
Both pesticides used to be used on farms until they were banned a few years ago. But they have continued to be found in rivers. In fact, with the development of more sensitive tests, they’re turning up “pretty much everywhere in waterways”, says Perkins.
Initially, it was thought this was a legacy of their use by farmers, but work by Perkins and others suggests parasite medications are now the main source of these pesticides in waterways. In many cases, levels are high enough to harm invertebrates such as mayflies, dragonflies and caddisflies, with knock-on effects on the fish and birds that feed on them.
We don’t know how big a problem this is, says the report. “The true scale of environmental harm resulting from pet parasite medications is not known.”
How are the pesticides getting into rivers? Once they’re applied to pets, they end up all over the home, says Perkins. When people bathe their pets or wash pet bedding, they can end in wastewater.
Product packaging currently recommends that dogs are not bathed for four days after treatment, but this needs to be extended to 28 days, the report recommends.
Another major source of the pesticides in water is hand-washing, says Perkins. “We detected [pesticides] in the wash-off even before we asked people to stroke their pets, so they’re just constantly on the hands of pet owners.”
Products containing fipronil and imidacloprid are now being replaced by ones containing isoxazolines, typically sold in the form of chewable tablets. Isoxazolines are less water-soluble but can bind to sediments and accumulate in soils and sewage sludge. They might be ending up in fields when sewage sludge is sprayed as fertiliser and harming pollinators.
“There has not been much work done to date to assess this,” says the report.
Shed dog fur is yet another way these chemicals can end up in the environment. The report says contaminated fur has been found in bird nests.
In light of these findings, the use of pet parasite medications should be minimised until there’s independent research clarifying their risks, says the report. At present, manufacturers of parasite treatments are promoting the idea that routine treatment for parasites is required, and encouraging pet owners to get them via monthly subscriptions. “However, the benefits of routine, and certainly monthly, pet parasite medicine usage are not supported by scientific evidence.”
It’s an excellent report, says Perkins, but she hoped it would go further and recommend making these products prescription-only. Some wildlife groups, meanwhile, want some of these products banned altogether.
Yet another reason for restricting their use is to slow the development of resistance, says Perkins. She sees a lot of animals treated with old spot-on treatments containing fipronil that still have fleas. “We need effective parasite treatments, and we need to make sure we preserve their efficacy,” she says.