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Biosecurity, sustainable livestock parasite control and messaging

Co-designing and implementing best-fit farming practices

Livestock disease workshop on Lewis and Harris

Roundworms and sheep scab mites are common throughout the UK and threaten the health, welfare and productivity of grazing livestock. Infections are commonly controlled using organophosphate dips and/or anthelmintics.  The development and dissemination of resistance to these compounds and variation in the epidemiology of roundworms resulting from changes in climate and farm management are making the sustainable control of these parasites more challenging, particularly roundworms.

This case study explores how to make parasite control guidelines targeted for their unique context (i.e. measures that can be practically taken up) and how to make materials easily accessible for sheep keepers.  The study used a multi-disciplinary approach between social scientists and parasitologists to investigate the areas fully.


Work in Progress


Best-practice recommendations for the control of parasites in sheep have been set out by the industry advice group “Sustainable Control Of Parasites in Sheep” (SCOPS).  The advice, which is freely accessible online, is aimed at producers and vets to help them make informed choices to ensure parasiticide products are only used when necessary.  Treatment administrations should ideally be supported by a diagnosis or a risk assessment that confirms the need to treat and/or to confirm the efficacy of those treatments. This approach avoids the unnecessary use of medicines, slows the development of resistance and minimises the environmental exposure to parasiticides. 

Biosecurity practices have been designed to prevent the introduction of sheep scab mites and anthelmintic resistant roundworms with new and returning stock (SCOPS advice). Understanding the risks that these pathogens pose to livestock productivity and the availability of diagnostic tests is beginning to gain traction within the livestock industry with the inclusion of faecal egg counting within both England’s Animal Health and Welfare Pathway and the Scottish Government’s “Preparing for Sustainable Farming” (PSF) initiatives (and the use of the sheep scab blood test (ELISA) in PSF). Despite this increasing forecasted demand, tailored resources and recommendations for producers in remote rural and Island settings are limited.

Therefore, understanding keepers’ knowledge and attitudes to parasite risk, available control options and how treatments can target multiple disease-causing agents is important if changes in behaviour are required.  Exploring, with sheep keepers, how to make guidelines targeted for their unique context (i.e. measures that can be practically taken up) and how to make materials easily accessible will help target knowledge exchange efforts.  As such, a multi-disciplinary approach between social scientists and parasitologists was taken to investigate these areas fully.


A collaborative group of researchers representing: The Moredun Research Institute (Strategies to promote sustainable parasite control and reduce anthelmintic usage) and The James Hutton Institute (Co-designing and implementing best-fit farming practices) visited Lewis and Harris to conduct workshops on biosecurity measures, Crofter behaviour and potential triggers of change, disease awareness, treatments and methods of roundworm and sheep scab diagnosis.

The workshops explored participants understanding of the term ‘biosecurity,’ knowledge of current ‘best practice’ biosecurity practices, barriers to implementation of recommendations and what the ‘best fit’ for their situation would look like. In addition, expert talks on roundworm and sheep scab identification and treatment/control were provided, and the Moredun bus (Figure 1) was on hand to allow practical demonstration and training of faecal egg counts and roundworm diagnostic methods to attendees. 

Figure 1: Moredun bus on Lewis and Harris, and internal set up for faecal egg counting workshop.

The training exercise was designed to demystify the technique (showing that it is simple to achieve, even on farm) and provide practical advice and materials (Figure 2) to help in the collection and processing of faecal samples to facilitate better results.

Figure 2. Materials describing how to collect suitable faecal samples for faecal egg counting and what roundworm eggs look like under the microscope.

In total, five training sessions were held, engaging a total of thirty-five crofters during the weeklong visit. The workshops offered an ideal opportunity to better understand sheep keepers’ behaviour towards disease control focusing on sheep scab and roundworm control.

Roundworm control

Limited studies have been undertaken on Lewis and Harris to look at roundworm infections or the anthelmintic resistance status of the worms in their sheep.  A benzimidazole (1-BZ) resistance prevalence survey conducted in Scotland in 2000 reported the highland and Islands region as having the lowest prevalence of white drench resistance, with almost 4 in 10 farms tested showing resistance compared to the country wide average of just over 6 in 10.  No further reported studies have been conducted since then.

Participants of the workshops reported that diagnostics were not commonly used either as a roundworm monitoring tool or for efficacy testing. A faecal egg counting service is not readily available on the island, samples can be sent to the mainland, but the cost and delay in obtaining a result means the process is underused.

Participants had limited awareness of the different anthelmintic drug classes, their ability to control both sheep scab and roundworms with anthelmintic products (macrocyclic lactone; 3-ML) and the potential impact that might have on developing resistance which was also not widely considered. Failure to effectively control roundworms leads to clinical cases of disease and in extreme cases, culling of flocks.  As such, developing sustainable control strategies that best utilise the small number of active compounds available is essential.  Purchasing options were often dictated by availability within the single agricultural stockiest on the island, some also bought products online.

The workshops also provided attendees with an opportunity to take part in a hands-on practical session identifying roundworm eggs in their animals’ faeces. The Moredun mobile laboratory provided an exciting opportunity for the crofters to gain firsthand experience in preparing and exploring samples for faecal egg counting (FEC). These resources are a unique way of engaging stakeholders, and the equipment and training are rarely available in more remote and inaccessible areas.

Sheep scab control

Outbreaks of scab have previously been reported on Lewis & Harris, and due to the highly connected nature of crofts and the use of common grazing, the disease is able to spread very quickly in this environment. This means that lasting control depends on coordinated efforts. Despite the previous outbreaks, most participants felt that the risk was low, and many crofters did not see the need to quarantine animals coming onto the island. However, participants in Ness, where there had been a recent outbreak (2017-18), showed a greater awareness of biosecurity measures, e.g. keeping fences in good repair and quarantining incoming stock, although some people felt complacency was creeping back.

Participants believed they could tell if an animal was healthy by observation alone, and many seemed unaware that sheep could carry the infestation without showing clinical signs of disease. Participants commented that there are many keepers on the island who don’t understand sheep husbandry or just have a few sheep on the hill that they never see, which are not being treated effectively, or at all. Treatment of sheep scab can be achieved by injecting macrocyclic lactones (MLs) or plunge dipping in organophosphate (OP). As only around 20-30% of sheep keepers gather their sheep for scanning, and OP plunge dipping is rare in some townships, it is highly likely that early scab infestations may be missed. When scab outbreaks occur, most farmers treated using either an OP plunge dip, collectively as part of an affected township or with an injectable ML, such as doramectin. However, many seemed unaware that the product is only effective for treating the disease and offers no continued protection against reinfestation in the ways that OP dipping, or more long-acting ML compounds do. Consequently, many crofters were unaware that once treated with doramectin, animals must be moved to clean pasture. In many cases, this may not be an option due to the limited pasture available in the crofting systems, so reinfestation is likely. It appears that treatment choices and outcomes can clearly be improved with increased knowledge of best practice control.

Historically, dipping was seen as a communal effort, with each township coming together to gather and dip their sheep using community-maintained fanks. More recently, however, due to a move towards greater use of the injectables and large gatherings becoming less feasible (fewer keepers and the population demographic being older), many dipping facilities have fallen into disrepair.

Participants at the workshops stated that there would be keen interest in a mobile dipping contractor from the mainland visiting to help to coordinate the dipping efforts. However, gathering sheep would still be an issue due to a lack of help available. At present, there are few keepers with large numbers of sheep using the hills, many of whom rely on paid help, often from the mainland, at gathering times.

Understanding attitudes to uptake of measures

Current guidelines for disease control are described using the term ‘biosecurity’ however crofters indicated that this term was not widely understood by them, although they do engage in some measures to control disease, showing disconnect between the term and the practical measures.

The measures adopted by the crofters are bespoke for their context, keeping sheep in small numbers, in remote areas and accessing the common grazing. The measures can be described as ‘best-fit’ for their context.

During the workshops it also became clear although industry advice groups like SCOPS offer clear advice they are largely unaware of these services highlighting the need to target messaging and re-focus knowledge exchange. Taking into account practical measures that can be achieved with small numbers of livestock in remote rural settings as seen on the island’s crofts would be beneficial.

Next steps 

The work has highlighted knowledge gaps and opportunities for development of resources to improve the uptake of diagnostic tools that will help the crofters in more remote regions to make more informed decisions on parasite control.


Importance of KE/collaboration and understanding

The crofters welcomed the training opportunity and were keen to understand the importance of using diagnostic methods.  The engagement with the crofting communities was positive, and attendees were keen to engage and collected printed information available during the workshops including flyers and disease/diagnostic sheets.  It was highlighted that there was a need for a range of information formats to be made available and that printed outputs still have a place. Using a range of KE formats will encourage engagement from a wider audience and not restrict access only to those that can access the internet.  Additional information on developing faecal egg counting facilities was requested both in their own communities and on an individual basis.

Further discussions were held between scientists at Moredun and the Lewis & Harris Sheep Producers Association (LHSPA) regarding blood testing some of the island's flock for scab. It was felt that the best opportunity for large-scale serological testing using the sheep scab blood test would be at pregnancy scanning. Approximately 250 farmers scan their sheep across Lewis & Harris, using a single scanning contractor, with the activity being coordinated by the LHSPA. This provides an excellent opportunity to test a large number of flocks across the island and will help to identify areas where further support could be focused.

Securing extra funding: The interaction led to further funds being leveraged from Livestock Health Scotland in conjunction with the commercial faecal egg counting company Techion to purchase two FEC systems (including technical support) and provide continued professional development to a number of SPA members with a view to a greater rollout.

Additionally, funding from SEFARI Gateway (Innovative Knowledge Exchange Fund) and the VMD enabled the development of a web resource FEC check to assist farmers and veterinarians in undertaking and interpreting faecal egg count results.

Since the workshops further funding has now also been secured from the Scottish Government to continue the sheep scab control project. Following the testing at scanning in February 2023, we aim to coordinate treatments via OP plunge dipping of sheep in affected areas using a mobile dipping contractor.

Resource development:

FEC Check: Understanding sheep roundworm egg count results at a glance | SEFARI

Sustainable Roundworm Control - Getting the Message Across | SEFARI

Finally, researchers have been working with the Shetland Animal Health Scheme to put together a virtual tour of the biosecurity processes for livestock entering the Shetland Islands, the primary action for this output was to share this with the crofters across other island communities such as those on Lewis and Harris, where such local bye-laws may be useful to improve biosecurity in the future.



Project Partners

Moredun Research Institute

The James Hutton Institute

Lewis and Harris Sheep Producers Association (LHSPA)


Livestock Health Scotland

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