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Anthelmintics and the Environment – opening a whole can of worms?

Anthelmintics and the Environment – opening a whole can of worms?

sheep being given anti worming and/or flukicide treatment

A SEFARI Specialist Advisory Group was established in response to concerns from livestock farmers and agro-ecologists about the adverse environmental impacts of some frontline livestock worming treatments, which reach the environment either in the dung/urine of treated animals or as a result of inappropriate disposal. Information on potential environmental impacts is a prerequisite for approval of veterinary medicines in the UK, but that information is not easy to find or understand.  Working with the two main industry-led groups (SCOPS and COWS) and the competent licensing authority in the UK (VMD), we aimed to collate available information and make it easier for farmers, vets and advisors to find and understand, so that they can make informed decisions around sustainable parasite control in the best interests of animal and environmental health.


Work Completed


The project was initiated following conversations with a number of livestock farmers, mostly engaged in conservation grazing programmes, who were concerned about the environmental impact of some of the wormers and flukicides they planned to use in their animals. There is well-established, published evidence of the adverse effects of some of the frontline products e.g. ivermectin and triclabendazole on dung beetles and associated fauna, but that information is not easy to find on product data sheets or in the public domain. As a result, many of the farmers were making odd and, in some cases, inappropriate, product choices. Others were using the meat and milk withhold periods i.e. the length of time active drug residues can be detected in meat and/or milk samples, as an indication of how long these chemicals might be active in the environment - these are not the same thing!

We don’t want farmers to stop using anthelmintics, nor do we want environmental agencies or lobby groups to advocate banning them; animal health and welfare must still be a paramount consideration. We want farmers to use the right product, at the right time etc. and to use ‘as little as possible but as much as necessary’, but there will be pressure to reduce chemical usage on-farm, and we need to be aware of any adverse environmental impacts, whether through usage and/or disposal.

The SEFARI A&E Specialist Advisory Group was based around the two industry-led Sustainable Control of Parasites in Sheep (SCOPS) and Control of Worms Sustainably (COWS) groups, who are the acknowledged and trusted source of guidance and best practice advice for farmers, vets and advisors, as well as the Veterinary Medicines Directorate (VMD), the competent regulatory authority in the UK. Other key contributors were academics engaged in research on anthelmintics and the environment, representatives of the veterinary pharmaceutical industry who manufacture and sell anthelmintics to farmers, as well as farmers, vets, ecologists, soil scientists, environmentalists and other interested parties (n>30).

Our regular ~6-weekly virtual meetings allowed the group to better understand each others’ perspectives and the current state of knowledge on environmental impacts and the regulatory framework around licensing veterinary medicines in the UK. The main aim of the project though, working closely with SCOPS, COWS and the VMD, was to collate available information on the environmental impacts of the main actives and make that information more readily available and easier to understand, such that farmers, vets and advisors could make informed decisions about if/when to treat and what with, and to promote animal health and welfare and the sustainability of the livestock sector, in its broadest sense.


  • The A&E topic was brought to the attention of the respective sheep and cattle industry groups, SCOPS and COWS
  • Both groups have set up Environmental Working Groups, chaired by representatives from the A&E Project team, and have issued a joint SCOPS and COWS statement on ‘Environmental Considerations’
  • ‘Environmental considerations’ message now included in latest iterations of SCOPS ‘Know Your Anthelmintics’ booklet and web resource, COWS equivalent to follow
  • The main outcome has been to raise awareness of the environmental impacts of anthelmintics, and that this information exists, but also to improve our understanding of the regulatory process around licensing of products through the VMD. 
  • The main output from the project has been, working with key personnel at SCOPS, COWS and VMD, to develop easy-to-understand resources to help farmers, vets and advisors make informed decisions, based on SCOPS and COWS product tables. 
  • The resources are still under development but are expected to be published later in 2022 so watch this space. 


The main benefit to emerge from the project is that the two main industry-led groups (SCOPS & COWS), who provide carefully crafted and trusted advice around best practice, are now more aware of the issues around anthelmintics and the environment, and better informed about sustainable control parasite practices in the broadest sense of the term. Both have statements about ‘environmental considerations’ on their respective websites, and have set up joint Environmental Working Groups to take this work forward and help develop further resources for farmers, vets and advisors. The A&E Advisory Group is also in liaison with the main industry levy boards to incorporate environmental information in future industry publications. We are also in discussions with the Animal Health Distributors Association (AHDA) and Animal Medicines Training and Regulations Authority (AMTRA) to include environmental considerations in Continuing Professional Development (CPD) training modules for Suitably Qualified Personnel (SQPs) and Registered Animal Medicines Advisor (RAMAs).

Our regular ~6-weekly virtual meetings throughout the year with the whole group (n=30), also allowed us to discuss a wide range of related topics, including the latest research and current state of knowledge around sustainable parasite control and the environmental impacts of anthelmintics. Discussed topics have included, amongst others:

  • The VMD regulatory process for licensing anthelmintics – Ken Stapleton
  • Conservation grazing – Richard Lockett
  • Farming without anthelmintics – Bruce Thomson
  • Changing epidemiology of gastrointestinal nematode parasites – Dave Bartley
  • Dung Beetles for Farmers – Sally-Ann Spence
  • The fate of ivermectin in stored manure – Bryony Sands
  • An ecological approach to liver fluke control – Iain Richards
  • A pen-side test for liver fluke – Diana Williams
  • Conserving Red-billed Chough on Islay – David Wood
  • Liver fluke and agri-environment schemes – Philip Skuce

Project Partners

  • Brian Boag, James Hutton Institute
  • Matthew Colston, Elanco Animal Health
  • Richard Lockett, Agro-ecologist
  • David Wood, RSPB Warden, Islay
  • Lesley Prior, Pedigree Sheep Breeder
  • Emily Grant, Sheep Consultant
  • Iain Richards, Eco-vet, BCVA
  • Claire Whittle, large animal vet, Nuffield Scholar
  • Sally-Ann Spence, Dung Beetles For Farmers
  • Bruce Thompson, Dairy farmer, Nuffield Scholar
  • Sara Gregson, COWS Group
  • Diana Williams, University of Liverpool
  • Patrick Laurie, Working for Waders
  • Claire Stratford, Veterinary Medicines Directorate
  • Ken Stapleton, Veterinary Medicines Directorate
  • Nia Ball, Scottish Government
  • Luis.Molero, Scottish Government
  • Kirsty.Hutchison, NatureScot
  • Rob Howe, large animal vet, BCVA, COWS
  • Freda Scott-Park, vet & organic farmer
  • Judith Taggart, small animal vet, One Health MSc