Water Affected By Pet Parasite Treatments, Study Reveals

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Water quality in the UK is a hot topic these days, hitting headlines on an increasingly regular basis thanks to issues such as storm overflow discharges, surface water runoff, pesticides, herbicides, algal blooms, drought, flooding… the list goes on and on, it seems.


And now, according to a new report from Imperial College London, it appears that there’s another growing problem that is having an impact on the nation’s rivers, lakes and streams – and that’s the use of parasite treatments and preventatives for our pets.


These parasiticides are often applied as spot-on treatments for cats and dogs to prevent or kill ticks and fleas, but these treatments contain toxic chemicals that are now making their way into rivers and ponds, especially in more built-up urban areas.


Many of the treatments contain neonicotinoids, which have been banned for use in agriculture because evidence suggests that they can have an impact on bee populations, as well as other pollinators – which we need for our food supply.


Currently, however, they are still sold as pet parasiticides because it was assumed that they didn’t reach the natural environment in sufficient doses to cause problems.


New research investigating river water and invertebrates has since found that these chemicals are present in urban environments and in such concentrations that they’re able to harm aquatic life, which could have a knock-on effect on the overall ecosystem.


Researchers from Imperial College looked at the two main pesticides that feature in these treatments: imidacloprid and fipronil. There are 138 pet products that are authorised in the UK right now that contain imidacloprid and a further 396 that contain fipronil.


The UK is a nation of animal lovers and it’s estimated that there are 25 million cats and dogs around the country, many of which will be treated using products such as these on multiple occasions throughout the year.


Once they’re applied on the animal, the products are absorbed into the body but stay in the skin, hair and excretions, which means that it’s possible for the chemicals to reach waterways through wastewater and combined sewer overflows.


This becomes particularly problematic when you consider that both fipronil and imidacloprid are both especially toxic for invertebrates like insects. For example, one monthly flea treatment for a bigger dog has enough imidacloprid to kill 25 million bees, while in aquatic environments insect larvae are at risk, including dragonfly and mayfly.


These species are especially important food sources for bats, birds and fish, so the wider ecosystem may well be increasingly affected by the presence of these chemicals as time goes on.


Off the back of these results, the researchers have called for an urgent review of risk assessments and prescribing practices to address the issue of these chemicals and the effect they’re having on the natural world.


Dr Andrew Prentis, visiting fellow in the Grantham Institute at Imperial College London and a member of Vet Sustain, said: “So far, our use of parasiticides for pets has focused primarily on the animal and human health benefits, but even these are not well evidenced. Chemicals that have been banned in one sector are used indiscriminately in another with seemingly little consideration of the possible risks.


“This not only results in increased pollution of UK waterways – which are under myriad threats from other sources of pollution – but could also lead to parasite resistance due to overuse. It’s time for a reassessment of clinical need and treatment recommendations.”


He went on to advise any dog or cat owners out there to have a conversation with their vet about what’s best for their animals, while helping to protect the environment. In much the same way that people only take antibiotics when they’re ill, it may be that it’s only necessary to apply parasitic treatments when pets are similarly afflicted.


Professor Guy Woodward – deputy head of the life sciences department at Imperial – made further comments, saying: “There is a clear and pressing need to develop a stronger evidence base for gauging the impacts of these chemicals and their mixtures in the environment – and in particular to bridge the gap the gap between single species laboratory studies, which are still the dominant approach in ecotoxicology, to the more complex reality in the field, where we still have very limited understanding, especially in urban aquatic ecosystems.”


The ecological impact of parasiticides


It’s fast becoming clear that pesticide pollution is one of the biggest threats to freshwater resources and ecosystems around the world. In the UK, many ecosystem services linked to water quality (such as food production, recreation, water storage and drinking water supplies) are being put at potential risk because of this kind of pollution.


In natural ecosystems, invertebrates make up a large proportion of food web biodiversity and, as such, serve an essential purpose for the transfer of nutrients and energy to higher trophic levels such as fish, mammals and humans.


Many different species depend on these invertebrates for food and it’s possible that changes to their abundance or behaviour could have ripple effects right across the food web, potentially compromising important ecosystem services that are of particular value to people.


Pesticide use has already been linked to pollinator collapse in agricultural systems the world over, including here in the UK… and even if application of these chemicals is reduced substantially, environment-based concentrations would still be of concern based on evidence taken from laboratory studies.


Research shows that freshwater invertebrates are typically the most susceptible to direct effects of pesticides such as imidacloprid, with toxic effects seen in fish, birds and mammals.


Past mistakes have also shown what the potential consequences could be for the natural world through the use of pesticides. For example, use of DDT led to biomagnification in apex predators including peregrine falcons and otters, which resulted in significant population declines in the 20th century.

And in 2013, a chemical spill in the River Kennet involving organophosphate chlorpyrifos led to collapses in some keystone invertebrates, as well as having both direct and indirect impacts across the food web, suppressing decomposition rates and triggering algal blooms.


Ecological damage could also be taking place right now because of concentrations of parasiticide active ingredients in waterways overlapping with those that cause mortality and other sub-lethal effects in non-target species.


The challenge now is to understand if, how, why and how much the negative impacts on a couple of species in the lab then translates to more complex systems in the natural world, with the aim being to build a strong evidence base in order to mitigate or prevent undesirable outcomes.


The strong urban signal


Given the results of this latest study, it seems that one issue of pet parasiticide pollution that requires particular attention is the urban element, perhaps unsurprising since the majority of humans and pets live in built-up areas.


The challenge will be to disentangle the separate effects of each individual chemical, as well as furthering understanding of how they interact with other stressors.


For example, in natural ecosystems, active ingredients in parasiticides are present alongside a wide range of other chemicals – and different combinations of chemicals can have a synergistic effect, potentially amplifying the impacts and putting invertebrates and other species at even greater risk.


Climate change may also exacerbate the situation, as increasing temperatures could alter the toxicity of the pollutant cocktail we now have in our freshwater resources. Temperature has an effect on the organism metabolic rates, which is what shapes food webs and ecosystems – but it can also shape other stressors, such as pesticides.


Average annual global temperatures are on the rise, which is cause for concern, but other large spatial gradients need to be considered as well, such as the urban heat island effect, which could change how pesticides work in the real world.


Thus far, however, lab studies have ignored the role that temperature has to play, which makes extrapolating results to real-world ecosystems difficult.


As such, the Imperial College London team is now calling for improved chemicals policy in the UK, with increased flexibility and consideration of new approaches.


They also want to see UK regulatory bodies to review legislation and consider the need for veterinary medication used on pets to undergo full environmental risk assessments.


Do you want to find out why water efficiency is so important? Get in touch with the team here at H2o Building Services today to see how we can help.