What is being done in the fight against sheep scab?

Sheep Scab is estimated to cost the UK sheep industry up to £202 million every year in lost production, testing and vet costs, and treatments.

It’s a disease we could well do without. In addition to the financial cost, it is a serious welfare issue, and for the sheep., just imagine that intense irritation 24/7 even before it gets to the stage where it’s visually obvious.

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Psoroptes Scotland has its share of the problem, and with sheep movements being the main source of spread, those moves take place across farm, county, and national borders. It is one of the easiest parasites and diseases to spread around, and seemingly, on an industry scale, one of the most difficult to eradicate. The last 50 years have seen numerous attempts, but with an estimated 10 – 15% of UK flocks affected at any one time and the problem having gotten worse since deregulation, it is sobering to think that we have at least to date, failed.

However, failure cannot be considered an option, and with all farms increasingly having to be more cost-conscious, an increased acceptance of the need to ‘be responsible’ and trade responsibly, and the pressure continuing on reducing reliance on chemicals and protecting the environment, there is a renewed energy to tackle sheep scab once and for all. All UK nations have run pilot projects to test ways to resolve scab in hot spot areas, and in Scotland to work on an island-wide basis to demonstrate how a coordinated approach, using the sheep scab blood test (ELISA) to check for scab antibodies, and bring farmers together to ‘own the problem’. Perhaps more importantly, once the disease has been tackled locally, it is crucial to ensure that plans are in place in terms of increased vigilance and biosecurity, to ensure that the area remains scab free. The sheep scab blood test is a game-changer, able to identify those silent sub-clinical scab cases and target valuable treatments where they are really needed.

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Sheep scab Industry bodies in Scotland, working closely with the Scottish Government are now combining forces and have created a Sheep Scab working group to drive a concerted effort to coordinate communication and raise awareness of the problems and solutions. This has also acted as a catalyst for new funding from the Scottish Government for a pilot project on the Western Isles of Lewis and Harris to demonstrate what can be achieved with the expectation that we can engender a wider roll out of the approach, hopefully making use of the Improving Animal Health and Welfare programme, funded to the tune of up to £1,250 per farm in Scotland.

To provide even greater reassurance that the industry is taking this seriously, the work in Scotland is being combined within a newly agreed UK-wide Sheep Scab Strategy that aims to pull all our nations together with similar approaches and support simultaneously. This comes at a time when increased levels of resistance to the injectable macrocyclic lactones (MLs) is being found and of course any treatment that isn’t 100% effective will leave a reservoir of disease that will spread again.

Phil Stocker

Because of this, there is a renewed focus on the use of organophosphate (OP) plunge dipping, and with dipping facilities on many farms now outdated and ongoing concern over dipper safety when facilities aren’t top-notch, a new generation of highly efficient and safe to use mobile dipping facilities has emerged.

We are at a stage now where no one has to bring scab onto their farms, although shared grazings present a particular risk. By using the tools that are now available to all farmers we can keep sheep scab out through the use of pre-movement blood testing, effective quarantining and testing of new arrivals, or seeking evidence of recent OP treatments, you can now avoid buying in more than you’d bargained for.

The project on Lewis & Harris has been running since October 2022 and involves working closely with the Lewis & Harris Sheep Producers Association and local crofters to co-design methods for sustainable, best-practice control of sheep scab on the islands. The situation on Lewis & Harris, is no better or worse than the rest of the UK. However, the heavy reliance on crofting systems and common grazing, which increases the risk of scab by almost 10-fold, means that support is required to get a grip on the disease in this unique environment.

The project started out with a series of island-wide workshops to increase awareness of the disease and how to control it. It then offered free sheep scab blood testing during pregnancy scanning with 1260 blood samples (12 sheep per flock) being taken across >100 crofts. When flocks tested positive, coordinated treatments were provided and the blood test was used to ensure treatment success. Although the testing identified areas of concern on Lewis & Harris, due to the high degree of connectivity between properties, an over reliance on common grazing and a genuine enthusiasm amongst the island crofters to deal with the issue, it became apparent that a broader control strategy was required to achieve lasting control.

This resulted in an ambitious plan for an island-wide, coordinated OP plunge-dipping campaign using a mobile dipping contractor.

The project offered support with the coordination and gathering of animals. It covered the additional cost of bringing the mobile dipper to the island, but the cost of treatment (OP dip) was covered by the individual farmers. Dipping occurred during October-November 2023 and resulted in almost 30k sheep over ~400 individual crofts, effectively treated within a short time frame, highlighting the high degree of stakeholder engagement and community buy-in.

The project also had an unexpected but significant societal benefit. By supporting crofters to come together through a collective enterprise, the project helped to rekindle the spirit of community working, lost in recent years due to the ageing demographic and further exacerbated by the COVID-19 pandemic. This has had a significant impact on the mental health of many of the crofters, who often find themselves working long hours in isolation, particularly through the winter months.

Crucially, the legacy of the project is being assured by dealing with any cases of scab that arose post-dipping (few and far between), preventing the re-introduction of scab via quarantine testing and treatments, particularly for hoggs returning from overwintering on the mainland as well as purchased tups. Finally, the coordinated OP dipping will be repeated this autumn, with most crofts already signed up and similar levels of support being provided for a second dipping season.

It is hoped that this highly ambitious project will provide a clear example of how scab can be controlled at the local and regional level, inspiring farmers in other areas of Scotland and the UK to work together to deal with this awful disease in a more sustainable way.