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Companion animal parasiticides and the environment

NOAH (National Office of Animal Health) represents the UK animal medicines industry and aims to promote the benefits of licensed medicines and solutions for the health and welfare of all animals.

NOAH and its member companies are proud of the benefits for animal health, animal welfare and human health, that veterinary medicines bring to pets and owners. NOAH supports the responsible use of parasiticides and wishes to challenge numerous elements of the PAN UK Position paper and Open Letter.

NOAH and its members care about sustainability and the health of the environment and wish to engage on this topic in an objective, science-based, evidence-led manner, which recognises that animal health and welfare needs must be met, while at the same time safeguarding the environment. Companies are committed to the importance of product stewardship; monitoring and reporting on product safety and efficacy throughout a product’s lifetime is a key aspect of this.

Veterinary medicines, including companion animal parasiticides, are essential for animal health and welfare and for the prevention of zoonotic disease – it is a good thing for society and for animals that products continue to be researched, developed and marketed.

Preventative treatment has an important place for parasites which are present all year round and for pets at risk of exposure. Fleas can cause a number of diseases in companion animals. Persistent scratching, chewing and licking, results in hair loss and irritated skin that can lead to further problems including dermatitis, lesions and anaemia1] . Problems caused by ticks include infections from the wound around a tick bite and the transmission of Tick-Borne-Diseases (TBDs) such as Lyme disease or tick borne encephalitis. Lice can cause eczema, skin irritation and discomfort with skin infections and weeping sores. Tapeworms, heartworms and hookworms can cause a number of health problems2. For a disease like canine heartworm, which is spreading geographically due to climate change, prevention rather than treatment is often the only realistic option.

Prevention of fleas, ticks and controlling worm infestations is an important step for preventing zoonotic disease spread to people. External parasites like fleas can cause bites leading to infections in humans, while ticks can spread ‘vector-borne diseases’ to animals and people. With pets and people living in such close proximity, fleas can jump from animals to their owners with the bites causing irritation and distress. This can disrupt that all-important bond between people and their pets. Flea infestations within households can negatively impact people’s wellbeing, as fleas can survive in clothes, bedding, curtains, furniture, and are often difficult to eradicate. By preventing ectoparasites in companion animals owners can break this cycle.

Internal parasites like roundworms or tapeworms can also infect people through accidental or improper handling of animal waste. In ‘at-risk’ populations such as the elderly, children, or immunocompromised, an infection with disease like Toxocariasis, which is caused by parasites, can have severe lifelong health consequences. Toxoplasmosis infection of pregnant women can harm the unborn child.

The principles of veterinary medicines regulation

A robust regulatory system is in place for veterinary medicines in the UK,  overseen by the Veterinary Medicines Directorate (VMD). The core principle of the regulation of veterinary medicines is the assessment of all benefits and risks, which is conducted by independent regulators.

During this process, all hazards and potential risks arising from use of the product are identified and considered along with the benefits for animal health the product brings. If these benefits outweigh the potential risks, the product can be approved.

This benefit/risk assessment considers the product’s safety (including human and environmental safety), quality and efficacy, and determines the product’s legal supply classification (who can prescribe/supply) together with any warnings to be placed on the packaging or restrictions that should be placed on the product’s use. Products will not receive a Marketing Authorisation, unless it is clear that the benefits of a product outweigh any potential risks it may pose.

Do veterinary medicines, whether used in livestock or companion animals, cause damage to the environment?

Any application for a Marketing Authorisation (licence to sell the product) must include an Environmental Risk Assessment (ERA) that details any potential risk posed to the environment. Any animal medicines not meeting the requirements of this environmental risk assessment are denied authorisation for sale or supply. For pet parasiticides even while certain hazards might be known or identified for an active ingredient, the ERA considers how the product will be used to assess the environmental exposure and the actual probability of a hazard occurring.  This assessment may result in warning statements and/or precautionary measures on the label to mitigate any risk identified in the process. Used appropriately in accordance with the manufacturer’s label and instructions, animal medicines pose minimal risks to the environment. In this way, the ERA considers the actual probability of exposure to a hazard occurring and considers how the product will be used when assessing whether use of the products will have a negative outcome.

After veterinary medicines are authorised, the efficacy and safety of products, including environmental safety, is kept under review on an ongoing basis by both companies and the regulatory authorities.

It is important that prescribers and users of these products carefully consider and follow the administration advice on the product labelling and packaging to responsibly use the product. NOAH has launched its ‘Paws to Protect’ campaign to improve pet owner awareness of the importance of reading and following the warnings and recommendations on the packaging and labelling provided with veterinary medicines.

Both regulatory authorities and animal health companies continuously review scientific evidence about veterinary medicines, on an ongoing basis. Using this evidence, the regulatory authorities assess whether changes are needed using evidence-based policies.

Parasiticides Action Network (PAN) UK position paper and Open Letter, November 2023

NOAH wishes to challenge numerous elements of the PAN UK Position paper and Open Letter, published on 1 November 2023.

  1. PAN UK reference to fipronil and permethrin as being carcinogenic, endocrine disruptors and having links to cancer.

 This is incorrect and does not reflect the scientific consensus amongst regulatory bodies. The current science and the data support a strong safety profile for fipronil and permethrin when used according to label instructions.  This includes human safety for those who administer the product to the animal or those who will be in contact with the treated animal.

The safety of all veterinary medicines, including the safety of people who administer the medicine or who will have contact with the treated animal, is kept under continuous, ongoing review by independent regulatory authorities who consider new science as it evolves and becomes available, and who keep the benefits and risks of veterinary medicines under continuous review.

Topical flea and tick treatments should not be confused with products for protecting plants/crops or products for household use. Animal health applications have specifically targeted uses, formulations, dosage forms, methods of administration, and packaging designed to optimise efficacy against fleas and ticks on animals while minimizing unintended exposure to household members. 

  1. PAN UK asks authorities to ban five active substances in veterinary medicines for dogs and cats that are not permitted or banned for use on agriculture crops in UK.

 The approval of active substances for use in plant protection products is based on a risk assessment for the different applications (for example spray application on crops). However, the exposure to humans, surface water or pollinators from these applications is not representative of exposure that results from use in companion animal treatment. Veterinary medicinal product (VMP) regulation and associated guidelines are specifically designed to assess potential risk from the use of VMPs and a specialised regulatory authority, the UK’s Veterinary Medicines Directorate (VMD) ensure that the products comply with all human and environmental safety standards of relevance.

While PAN UK refer to new analysis of official Environment Agency river water quality data, it must be noted that government expert regulatory agencies including the Environment Agency and the Veterinary Medicines Directorate have formed a cross government Pharmaceuticals in the Environment (PiE) Group to enable discussion and knowledge exchange relating to pharmaceuticals in the environment from human, veterinary and, where there is cross over, agricultural and non-agricultural sources. In summary, government agencies are monitoring these matters closely.

  1. PAN UK, Greenpeace, the RSPB, The Rivers Trust and Wildfish, and the PVA call on the UK Government to ban all pesticide substances from pet medicines if they are not permitted in agriculture.

The sweeping call to ban “all pesticide substances from pet medicines if they are not permitted in agriculture” would lead to a ban of many companion animal parasiticides, leading to a significant reduction in the range of available products for companion animal treatment and consequently impact on animal health and welfare. Few of the active ingredients used in companion animal medications are also used in agriculture.

  1. If the five pesticide active substances were banned for use on dogs and cats, would there still be alternatives available?

PAN UK states that if the active substances listed were banned for use in medicines for dogs and cats, there would still be plenty of other medicines available. Specifically:

  • 153 ectoparasiticides • 160 endectocide.

It is important to clarify that the numbers quoted are numbers for actual veterinary medicinal products that are produced by several animal health companies and are not actually the number of active substances, as some brands may contain the same active substance. The active ingredients in many of the remaining products are not registered for use in agriculture and thus would potentially be banned under PAN’s sweeping call for restrictions.

While some alternatives for the treatment of fleas and ticks would remain available, the question of access to treatments is overlooked in the PAN UK paper. The majority of alternatives that would remain available are Prescription Only Medicines-Veterinary (POM-V) products, meaning they are only available with a prescription from a veterinary surgeon.

Animal owners have been able to obtain pet flea, tick and worm treatments from sources other than vets for many years and this has served animal health and welfare needs well. These treatments that are available from routes other than vets, are also authorised veterinary medicines, regulated by the Veterinary Medicines Directorate, who have decided as part of the authorisation process that they can be made available to animal owners, via these alternative routes.  There is no evidence that products being available for pet owners via different supply routes is a concern.  It would not be an appropriate or proportionate step to take to remove from the market many of the options that are available via this route. It would limit animal owner access to these important products with an associated negative impact on companion animal health and welfare and on human health.

Such a change could also lead to lack of access to animal medicines leading to animal owners skipping necessary treatments. It may also lead to owners accessing unregulated and unproven products or products from unregulated sources, with the associated dangers this poses.

  1. Where is the evidence that chemicals found in veterinary medicines are negatively impacting the environment?

PAN UK states that while the amount of research conducted on this topic is currently fairly limited, there is certainly sufficient evidence of environmental harm for it to be an area of concern, and arguably to justify taking a precautionary approach.

Whilst certain pesticides have been detected in certain UK rivers, the origin of these is not clear, as pesticides often have had multiple uses for many years, for example as biocides, pest control, commercial horticulture, agriculture and even imported treated textiles. Furthermore, another PAN-paper reports on continued uses of banned pesticides under derogations and exception regimes.4 There is also no evidence that the levels detected have caused any environmental harm.  Currently, there is no evidence of harm to the aquatic environment from the use of veterinary medicines. Any new monitoring data will be closely examined by NOAH and its members, who continue to take this matter very seriously.

A paper by Anthe et al3 published in the peer reviewed journal, Environmental Sciences Europe, titled “Development of an aquatic exposure assessment model for Imidacloprid in sewage treatment plant discharges arising from use of veterinary medicinal products” (2020) has also considered this matter. The exposure modelling used in the paper was based on an established approach used in the biocides area. This paper concluded that current uses of ectoparasiticidal veterinary medicines for pets make only a very small contribution to the results of the UK water monitoring program.

Further studies are expected to be published concerning this issue, which animal medicines companies and independent regulatory authorities will consider carefully when they are available. The development of further data is welcomed by NOAH to ensure an evidence-based approach to the subject continues to be taken.

Veterinary medicines are unlikely to be the main source of detected pesticides in aquatic environments3. The UK Government view is that there is not currently a case to take any action regarding veterinary medicines or their approach to ERAs and that, instead, further evidence is required. Several scientific studies are underway to investigate this further.

  1. Why are PAN UK calling for a ban?

PAN UK state that while voluntary and stewardship approaches may work in other areas, such as antibiotics, they have repeatedly proven to be ineffective at reducing pesticide-related harms to either human health or the environment for a number of key reasons, including:

Hazard vs. risk-based approaches – Arguably the most fundamental problem with voluntary and/or stewardship approaches to reducing pesticide harms is that nothing is as effective as removing the hazard itself. The UK (along with the EU) currently follows what is commonly called the ‘hazard-based’ approach to pesticide regulation. This means that if an active substance is judged to be intrinsically dangerous – for instance by being able to cause cancer or persistent pollution – then it is too hazardous to be used safely and should be banned. This approach is highly effective at reducing pesticide-related harms and is relatively simple to operate, but can be criticised for reducing the range of pesticides available. The hazard-based approach is underpinned by the precautionary principle, which emerged in the 1970s, and theoretically underpins all current UK decision-making on pesticides. It allows regulators to adopt precautionary measures when scientific evidence about an environmental or human health hazard is uncertain and the stakes are high. Under the precautionary principle, regulators do not have to wait for the evidence of harms to be definitive, an often-unattainable goal.

The reason that a hazard-based approach using the precautionary principle is not appropriate for regulation of companion animal parasiticides, is that while the active ingredient used in a plant protection product may be similar, or even the same as those used in anti-parasitic veterinary medicines, the exposure of, for example, bees and other insects to the ingredient may be very different, depending on whether the products are used in plant protection or for animal health.  To investigate this, an Exposure Assessment is carried out as part of the Environmental Risk Assessment process. The Exposure Assessment attempts to identify who or what may be exposed to the ingredient, the exposure route and how much they may be exposed to. When this process is undertaken for veterinary medicines, the regulatory authorities may conclude that the environmental risk posed by an ingredient is quite different for veterinary medicines than for plant protection products, even where the same or similar active ingredient is used.

The use of a hazard-based approach would mean looking at the properties of parasiticidal active ingredients (considering any hazards) in isolation and does not take into consideration how these products are actually used in veterinary medicines. Environmental exposure of active ingredients when used to treat pets is usually very low. The principle of banning a product because it has potential for harm would jeopardise the availability of all parasiticides and many other veterinary medicines, with severe consequences for animal and human health.  The regulation of veterinary medicines is therefore based on a benefit/risk rather than a hazard-based approach.

It is important that prescribers and users of these products carefully consider and follow the administration advice on the product labelling and packaging to responsibly use the product. NOAH has launched its ‘Paws to Protect’ campaign to improve pet owner awareness of the importance of reading and following the warnings and recommendations on the packaging and labelling provided with veterinary medicines.

  1. Are veterinary medicinal products killing bees and harming the wider environment?

Based on the current regulatory scientific consensus, the risk of exposure of insects and bees to these compounds is considered to be negligible when they are used in companion animals. Bees don’t feed on companion animals or their excreta. Sensationalising the impact of these products on the honeybee could be seen as misleading as there is no realistic exposure scenario to bees from parasiticides administered to companion animals which could have an impact on bees. The environmental safety of veterinary medicines is constantly monitored and kept under review by both the regulatory authorities and the companies that make them to inform regulatory policy for the future. At present, there is no evidence that would indicate that changes are required to the regulation and availability of these products, which play an important role in the maintenance of animal health and welfare.

  1. Is year-round treatment against parasites unnecessary?

Preventative treatment has an important place for those parasites which are present all year round and for pets at risk of exposure. The consequences of failing to prevent certain parasites can have a high cost, not only to pets and their welfare, but also to pet owners due to the distress caused. People frequently live with their pets in the home with pets living closely alongside their owners and integrated into lifestyle throughout the home increases risk of exposure to zoonotic diseases. The decision on the most appropriate parasiticide regime for any given pet will also depend on the pet’s lifestyle and behaviours, local parasite concerns and any zoonotic potential.

A failure to prevent disease can also have a negative impact on human health, as some parasites, or the diseases they carry, can also infect people. While flea infestations peak in summer and autumn, the European Scientific Counsel for Companion Animal Parasites (ESCCAP) UK and Ireland, state in their guidelines for the control of ectoparasites in dogs and cats1, that flea infestation can occur throughout the year and that year-round flea control is sometimes necessary and remains important to minimise the risks of UK household infestations (  Factors such as milder winters associated with climate change and the widespread use of modern central heating systems help to ensure that ectoparasite infestations can occur all year round. Furthermore, if animal owners rely purely on detecting fleas on the pet, at this stage there will be an environmental infestation requiring both treatment for the pet and also potentially environmental control measures such as household sprays to clear the infestation. This demonstrates the importance of prevention rather than treating such infestations.


  1. European Scientific Counsel Companion Animal Parasites (ESCCAP), ‘Control of Ectoparasites in dogs and cats, Seventh Edition’. Available at: (Accessed 9 October 2023)
  2. European Scientific Counsel Companion Animal Parasites (ESCCAP), ‘Worm Control in Dogs and Cats, Sixth Edition’. Available at: (Accessed 9 October 2023)
  3. Anthe, M., Valles-Ebeling, B., Achtenhagen, J. et al. Development of an aquatic exposure assessment model for Imidacloprid in sewage treatment plant discharges arising from use of veterinary medicinal products. Environ Sci Eur 32, 147 (2020). Available at: (Accessed 09/10/23).
  4. PAN-Europe (2023). Banned pesticides still in use in the EU | PAN Europe ( (Accessed 03/11/2023).

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