Dogs love ponds. They love playing in water. And many have received flea and tick treatments. Many of which are based on the insecticides fipronil and imidacloprid. These are toxic to bees and insects in general. You can see the problem, which has been highlighted in a recent study, the results of which are summarised in the infographic below.
More: One monthly imidacloprid cat or dog flea treatment could kill up to 25 million bees
Fipronil and imidacloprid are both insecticides that target the nervous systems of insects, including bees. They are part of two different classes of insecticides: fipronil is a phenylpyrazole, while imidacloprid is a neonicotinoid. Both chemicals are highly toxic to insects, including beneficial pollinators like bees, though their mechanisms of action differ slightly. Here’s how they work and their specific toxic effects:
Fipronil
- Mechanism of action: Fipronil disrupts the GABA (gamma-aminobutyric acid) receptors in the insect’s nervous system. GABA is a neurotransmitter that inhibits neural activity. When fipronil binds to GABA receptors, it blocks the inhibitory function, leading to an overactivation of the nervous system.
- Effect on insects: This overactivation causes hyperexcitation of the insect’s nerves, leading to paralysis and eventually death. For insects like bees, exposure to fipronil can result in a wide range of behavioral disruptions, including disorientation, reduced foraging efficiency, and inability to return to the hive.
- Toxicity to bees: Fipronil is highly toxic to bees both by ingestion and contact. Even at sublethal levels, it can cause significant harm by affecting their ability to forage and navigate. Field-realistic doses have been shown to impair bees’ learning and memory, crucial for their survival and hive duties.
Imidacloprid
- Mechanism of action: Imidacloprid acts on the nicotinic acetylcholine receptors (nAChRs) in the insect nervous system. These receptors are critical for transmitting nerve signals. Imidacloprid binds to these receptors and causes constant stimulation, disrupting the normal function of the nervous system.
- Effect on insects: Insects exposed to imidacloprid experience nervous system overstimulation, which leads to symptoms like tremors, disorientation, paralysis, and death. This overstimulation interferes with the insect’s ability to function normally.
- Toxicity to bees: Imidacloprid is extremely toxic to bees, particularly through exposure to contaminated nectar, pollen, or direct contact with treated plants. Like fipronil, imidacloprid can cause sublethal effects at low doses, such as reduced foraging, impaired navigation, and weakened immune responses. Chronic exposure can lead to colony collapse, where worker bees fail to return to the hive, which weakens the colony.
Key Impacts on Bees
- Impaired Navigation: Both fipronil and imidacloprid interfere with bees’ ability to navigate back to their hives. This causes disorientation and leads to worker bees getting lost, which can severely impact hive survival.
- Reduced Foraging Efficiency: Bees exposed to these chemicals often forage less effectively. They may struggle to locate flowers, collect pollen, or produce sufficient food for the colony.
- Colony Collapse Disorder (CCD): Chronic exposure to these insecticides is a contributing factor to Colony Collapse Disorder. CCD is characterized by the sudden disappearance of worker bees, leaving behind the queen and immature bees, which ultimately causes the collapse of the hive.
- Sublethal Effects: Even small, non-lethal doses of fipronil and imidacloprid can harm bees by disrupting their cognitive functions (learning and memory) and their immune system, making them more vulnerable to diseases and parasites.
Environmental Impact
- Both insecticides persist in the environment, contaminating soils, water sources, and non-target plants. Imidacloprid, in particular, is systemic, meaning it gets absorbed by plants and spreads throughout the tissues, including the nectar and pollen that bees collect.
- Bees that come into contact with these chemicals in their environment suffer not only from direct toxicity but also from the long-term effects on their colonies.
Conclusion
Fipronil and imidacloprid are highly toxic to bees and other beneficial insects. They work by disrupting critical neurological functions, leading to paralysis and death, while even small doses can cause harmful behavioral changes that weaken colonies. Their widespread use has raised concerns about their role in the decline of pollinator populations and overall biodiversity.
Banned from agricultural use
Fipronil and imidacloprid are both banned (since 2018) for use in agriculture in the UK due to their harmful effects on bees and other pollinators.
1. Fipronil
- UK status: Fipronil is banned in agriculture across the UK and the European Union (EU). It was banned by the EU in 2013 for use in agriculture because of its toxicity to bees, particularly through exposure to dust generated from the treated seeds and its long-lasting presence in the environment.
- Allowed uses: Fipronil is still used in some restricted settings, like veterinary products for controlling fleas and ticks on pets, but its agricultural use is prohibited due to the risks it poses to pollinators and non-target insects.
2. Imidacloprid
- UK status: Imidacloprid, a neonicotinoid insecticide, is also banned for outdoor agricultural use in the UK. The UK follows the European Union’s 2018 decision to ban the outdoor use of three neonicotinoids, including imidacloprid, due to the mounting evidence of harm to bees and other pollinators.
- Allowed uses: Similar to fipronil, imidacloprid’s use is restricted to certain controlled environments, like greenhouses, where there is minimal risk of exposure to bees. However, its outdoor agricultural application is banned.
Reasons for the Ban
- Both chemicals were banned because of their role in the decline of bee populations, which are essential for pollination and biodiversity. Scientific studies, many of them conducted by EU regulatory bodies, found that these insecticides have both lethal and sublethal effects on bees, impairing their navigation, foraging, and survival.
The UK’s ban is in line with the EU’s strict regulations on chemicals harmful to pollinators. However, there have been instances where emergency authorizations have been granted to use neonicotinoids under specific circumstances (e.g., sugar beet crops in the UK in 2021), but these exceptions are rare and controversial.
The research
Here’s some more information about the research. It has been published in the journal Science of the Total Environment. The researchers studied 18 ponds on Hampstead Heath, in North London, UK, including bathing pounds. There are three separate ponds on Hampstead Heath in which dogs are allowed to swim. Sometimes dog owners allow their dogs to swim in restricted ponds.
The researchers tested three ponds were dogs are allowed to swim and three ponds were dogs are not permitted to swim and also six streams that fed into these ponds.
As mentioned in the infographic, the ponds in which dogs are allowed to swim contained high levels of these insecticides which are harmful to invertible organisms.
The chemicals were not detected in pounds were dogs are not permitted to swim. In connecting streams there were small amounts of these chemicals. They did not test the water where humans were allowed to bathe.
But one of the bathing pools for humans was downstream of a dog swimming pond and low levels of the chemicals were found in the connecting stream.
It seems that the pesticides are absent from ponds where humans are allowed to swim.
Leon Barron, from Imperial’s School Of Public Health, said: “This work adds to the growing body of evidence that will hopefully lead to changes in prescribing practices and advice given to pet owners. But as the public can buy these products without restriction in supermarkets, we need to raise awareness among dog owners.”
The researchers spoke to 101 dog owners and 86 of them were “unaware of the potential impacts” of the pesticides. This is why I have written this post and produced the short Infographic. We need to be aware of this problem.
Cats present a similar problem
In fact, we need to be fully aware of the toxicity of the chemicals used to control fleas and other ectoparasites on dogs and cats in general. A similar problem is presented for cat owners. Cats don’t swim in public area ponds or rarely do so but they are often treated with insecticides and not infrequently their owners bathe them.
That water will be washed into the wastewater systems from where it can enter waterways and harm nature. And as seen in the infographic below when cat owners wash their hands after administering the treatment the chemicals are washed into the waste water system – see link below the image.
More: Cat flea treatment insecticides are poisoning aquatic life in rivers