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Imperial College Report on pet parasiticides: NOAH position

The report from Imperial College London (published 21 March 2023) ‘Are urban areas hotspots for pollution from pet parasiticides?’ reviews much of the existing information on potential risks from treating and preventing parasites in our pets. We welcome this briefing for drawing this together, and NOAH is always ready to collaborate with all parties on this topic in an open, and scientific manner.

NOAH companies agree that parasiticides should be used based on the risk posed to the animal and the pet owner, and are open and willing to work with the relevant stakeholders to achieve this.

For complex topics like this we believe the One Health Model is a pragmatic way to base the discussion, where human, animal and environmental health are represented equally. We remain concerned regarding the extent to which these veterinary medicinal products are so important for our animals’ health and welfare, public health and the important relationship between pet owners and their pets does not seem to be fully recognised.

Importance of preventive treatment

Preventive treatment has an important place for parasites which are present all year round and for pets at risk of exposure. The consequences of failing to prevent parasites can have a high cost, not only to pets and their health and welfare, but also to pet owners due to the distress caused, with possible consequences for the human-animal bond.

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[1]. Untreated animals can be asymptomatic while excreting infective forms of the parasite in the environment, which represents a threat to humans, especially to vulnerable groups like children and immunocompromised adults.

While ectoparasites infestations peak in summer and autumn, the European Scientific Counsel for Companion Animal Parasites (ESCCAP) UK and Ireland state in their guidelines[2] for the control of ectoparasites in dogs and cats, that flea infestation can occur throughout the year and that year-round  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 preventing rather than treating such infestations.

There are multiple potential sources of the substances that have been detected including biocides, pest control products, agriculture and even imported treated textiles and food. It is important that any investigation of sources is comprehensive.

Extensive evaluation by the relevant regulatory authorities

The Veterinary Medicines Directorate (VMD) is responsible for the regulation of veterinary medicines. Before being placed on the market, all veterinary medicines undergo a detailed regulatory assessment by the regulators, who consider the balance of the benefits provided from using the product, compared with the potential risks. This benefit/risk assessment considers the product’s safety (including 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. The Review implied that some products were still on the market due to a loophole in the law which is inaccurate, as all products currently licensed have been through the independent VMD assessment, authorisation and registration process.

User advice including precautions for pet owners

In line with their requirements, pet parasiticides are accompanied by comprehensive user advice including precautions pet owners should take around handling, bathing and allowing treated animals into watercourses in order to ensure efficacy and to avoid environmental release. It is important that prescribers and end users of these products carefully consider and follow the administration advice on any veterinary medicine labelling and packaging, as this includes important mitigating factors on using products safely and effectively. Pet owners have been able to access pet parasiticide treatments from a number of sources in accordance with the product’s marketing authorisation category(vets, SQP, online or retail / over the counter) for many years and this has served animal health and welfare needs well. Regardless of where pet owners get their parasite control products from they should carefully read the product packaging before use of the product and follow the instructions regarding product administration and disposal. While more can be done to improve pet owner awareness and responsible use, encouragingly, a recent NOAH survey showed that 78% of pet owners are aware of and adhere to usage instructions of parasite prevention products every time they use them (3), and we are working to raise awareness of the importance of doing so to those that find it difficult or are not aware.

In summary

While NOAH supports Imperial College’s call for collaborative, evidence-based policy decision making, and that further research is conducted to fully understand some of the gaps highlighted in the report, NOAH would be pleased to be part of this process. Key to this, it is important that the health, welfare and societal benefits of preventing parasites in pets and households is not overlooked.

For further information see

[1]    Pathogens in fleas collected from cats and dogs: distribution and prevalence in the UK – PubMed (

[2]   European Scientific Counsel for Companion Animal Parasites (ESCCAP) UK and Ireland guidelines for the control of ectoparasites in dogs and cats

[3] Understanding the challenges to pet care in 2022 and the impact of the cost-of-living crisis on pet ownership: A report prepared for NOAH (Kantar, February 2023) p49,

27 March 2023

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