Flea and tick treatments, such as those containing the active substances fipronil and imidacloprid, have insecticidal activity that also has the potential to impact non-target insects.  

Historically, this has not been deemed to be a risk as exposure to the environment from use of these medicines has been anticipated to be negligible, based on their use as individual treatments for pets.  Recent monitoring has detected imidacloprid and fipronil in UK surface waters at levels that may potentially be toxic to aquatic insects.  As both these substances have been banned for use as pesticides in the agricultural sector, flea and tick treatments have been publicly implicated as a major potential source.

In response to these concerns, the VMD commissioned research to investigate the potential environmental exposure pathways for flea and tick products.  Findings suggest that use of certain topical flea and tick treatments can contribute to levels of imidacloprid and fipronil in the environment, particularly via wastewater.  This is considered to be key evidence, which will be taken forward internally as well as by the cross-Government Pharmaceuticals in the Environment Group.

See our gov.uk page for published updates on the PiE Group.

As the regulator for veterinary medicines, we establish the suitability of any active substance for use in a veterinary medicine independently of other regulatory frameworks. One of the significant factors taken into account, during our independent assessment, is balancing the benefits of using a veterinary medicinal product for animal health and welfare reasons, and for the benefits to human health, when weighed against the risks, including risks to the environment. Products will only be authorised where the benefits of use outweigh the risks.

In this instance, the medicine plays a vital role in treating fleas and ticks, which can lead to parasitic disease in pets and present zoonotic risks to humans, as well as causing distress and discomfort. Companion animal parasiticides, therefore, form an important part of effective parasite control to protect both human and animal health and welfare.  We will continue to take a balanced approach on veterinary medicines to ensure the benefits of use outweigh risks. The cross-government Pharmaceuticals in the Environment Group is considering how we best mitigate against the impacts of pharmaceuticals on the environment (biodiversity).  Any actions related to veterinary medicines will be driven by the strategy developed by this Group and wider international agreements.

Ectoparasiticides are medicines intended to kill external parasites (ectoparasites) that live on the outside its host, such as ticks and fleas. Endectocides are medicines intended to kill ectoparasites as well as internal parasites that live inside its host (endoparasites), such as parasitic worms. 

Exposure to fleas and ticks can lead to parasitic disease in pets, as well as causing distress and discomfort. Some of these parasitic diseases can also be transferred to humans. Ectoparasiticides and endectocides (parasiticides) form an important part of effective parasite control to protect animal health and welfare as well as human health. It is therefore essential to take a balanced approach in terms of authorising these products.

Although there is now evidence that demonstrates that use of flea and tick treatments can contribute to the levels of pollution detected in surface water, several gaps in our knowledge still remain.  We still do not have a strong understanding of the actual impact on ecological health of the levels of fipronil and imidacloprid that are currently being detected.  

We also need to develop a better understanding of other potential sources, such as biocides and residues from manufacturing and imported goods.  The possible negative impacts on animal health and human health in changing usage patterns of these veterinary medicines also need to be considered.

The VMD has led on the formation of a cross-governmental Pharmaceuticals in the Environment (PiE) Group, in order to provide a platform for discussion and knowledge exchange relating to pharmaceuticals in the environment from human, veterinary and, where there is cross over, agricultural and non-agricultural sources. 

The Group aims to develop a co-ordinated strategy to reduce the impacts of pharmaceuticals on the environment (biodiversity). The Group’s first priority area is to gain a better understanding of the potential sources of fipronil and imidacloprid levels detected in UK surface waters and to work towards reducing these levels.

Alongside this, the VMD and the Environment Agency (EA) are working closely together to improve our understanding of the risks posed by chemicals in the water environment and to respond appropriately. This includes continued EA monitoring of rivers for chemicals, including insecticides and other pesticides, to enable us to identify and act upon any emerging issues associated with their use and occurrence in the environment.

Whilst the VMD are prioritising the development of evidence-based actions around the impacts of veterinary medicines on the environment, working to resolve this issue will require involvement by all key stakeholders, including industry and veterinary professionals. 

The VMD are aware of various other initiatives and academic research occurring that are evaluating the need for changes to the assessment for pets. We are supportive of these efforts and encourage stakeholders to engage with the VMD in order to facilitate proactive collaboration and move forward with this important issue.

All veterinary medicines undergo rigorous scientific assessments prior to approval, in line with International Cooperation on Harmonisation of Technical Requirements for Registration of Veterinary Medicinal Products (VICH) guidelines. 

To address safety for ecosystems, an environmental exposure assessment is conducted for every veterinary pharmaceutical, referred to as a Phase I exposure assessment. If exposure to the environment is thought to be high, an in-depth ‘Phase II’ risk assessment considering the expected exposure and toxicity is performed to further evaluate risks to the environment. The findings from this assessment are factored into the decision whether to approve a veterinary medicinal product. At present, pharmaceuticals for companion animals typically end at Phase I, as VICH guidelines stipulate that environmental exposure from use of these types of products will be negligible. 

Although the VMD acknowledge that there are still several evidence gaps remaining and are working towards filling these gaps, we now consider that there are sufficient data to support a review of the internationally agreed VICH Environmental Risk Assessment guidelines.

Although imidacloprid and fipronil are toxic to insects, they have a high margin of safety for mammals, including humans.  

To address human safety, applicants must carry out a user risk assessment, which takes into consideration data on pharmacology and toxicology of the substances included in the product in order to determine the likely hazards to human users (and family members including children, where the products are used in the home), and the likely exposure (routes and extent) of the people involved.

These data are then combined in a risk assessment which determines the likely risks and then mitigates for them. The risk mitigations can be in the form of user safety warnings that appear on the product packaging, or in other ways, such as having child-resistant closures.

Once a product is authorised, it is then subject to post marketing surveillance, also known as pharmacovigilance. The Marketing Authorisation Holder has a legal responsibility to report to the VMD any reports of adverse events it receives relating to the use of the product on the animal, any adverse events experienced by those administering the product to the animal or animal owners, any adverse events to the environment and also whether there is a lack of efficacy.  

Current pharmacovigilance data show that <1 adverse event in humans is reported per 10,000 doses administered for fipronil and imidacloprid stop-on treatments. 

Anyone can report a reaction to a veterinary medicine that affects a person, animal or the environment. You can also report if an animal medicine has not worked. There are several ways to report: 

• To your vet or retailer: It’s a good idea to let your vet know if your animal has experienced a reaction. 
• To the Marketing Authorisation Holder (MAH): Contact details are always given on the product packaging and leaflet. MAHs must collate this information and provide the VMD with regular safety updates which includes all reports.
• To the VMD: Anyone can report adverse event directly to us, even if you have already reported it elsewhere. The MA holder will share any adverse event reports with the VMD, so there is no need to report twice.  
• Report a suspected problem with an animal medicine or microchip

The VMD’s pharmacovigilance team continuously monitor all authorised veterinary medicinal products for adverse events by analysing reports received. A significant number of reports with the same or similar event could indicate a problem with a product. When appropriate, we may look to add additional warnings on the product’s packaging or request changes to how the product is used. We can also suspend or revoke a the marketing authorisation, if there is sufficient evidence in the data to show that the benefit:risk balance is no longer considered positive. Any changes must be supported by data to ensure that the proposed amendments are appropriate and that the benefits of authorising the product continue to outweigh the risks.

Pet owners are encouraged to read the package leaflet and ensure that they are administering the product correctly and adhering to the specific advice concerning environmental risks, such as keeping treated animals out of water courses for a limited time after treatment.  

If the product literature has been misplaced, this information can be accessed via the VMD’s Product Information Database by searching for the product in question. 

Used pipettes should not be rinsed and should instead be disposed of via household waste.