M2: Sheep scab: scratching beyond the surface
Chair: Anna Bassett (Livestock consultant)
Sheep scab is an extremely contagious disease that has an impact both on welfare and economic return. Organic farmers have limited options for treating scab so the organic principles of management to promote health and avoid disease are of extreme importance. The session focuses on the extent of the problem and provides an assessment of pros and cons of current methods of control and treatment options. It also provides an update on current research and an insight into practical eradication programmes and campaigns. There will be an opportunity to ask our veterinary speakers about other livestock health issues. (Organised by the Soil Association)
Sheep scab, an allergic dermatitis, is an extremely contagious disease that was eradicated in UK in 1952 and is now prevalent due to ineffective management and treatment usually by less than 5% of sheep farmers. Numerous studies and surveys have highlighted the huge economic cost to the sheep industry. Sheep keepers now commit a criminal offence if fail to treat visibly affected sheep. Identification remains a problem and leads to misdiagnosis and cross infection. Failure to carry out strict quarantine for 21 days of sheep new to holdings results in rapid and wide spread of this and other contagious/infectious sheep diseases. Simple measures that can be taken to reduce spread include double fencing, quarantine of new sheep, thorough cleaning of transport and handling areas. Organic farmers are particularly at risk from neighbours or conventional flocks as much of organic practices should help with prevention (closed flocks, quarantining, traceable sources of any new organic /conventional stock into the flock). Use of treatment in quarantine may reduce need for treatments and prevent spread into flock and be discussed with CBs in context of health planning. Upland breeds tend to be more resilient than lowland and survivors rarely succumb a second time but will have exposed rest of flock to the mite. Despite the knowledge available ram sales continue to be too late in the season for effective quarantine.
- Use quarantine effectively for 21 days and consider preventative treatment
- Use of closed flocks in organic systems assists with control (but care needed with rams from other farms)
- Need co -operation on common land or with neighbours where sheep are in contact
- Diagnose carefully & treat accordingly
- Small proportion of sheep farmers cause the problem for the industry as a whole
- Vaccine development difficult but in progress
- A pre- clinical Serological test is on the horizon
- Get messages across to (organic) sheep farmers improve the identification/diagnoses rates
- Communicate issues with NSA – organic sheep producers have ram sales earlier in the season and lead the way?
Individual speaker presentations and abstracts
Arjen Brouwer (Vet. Advisor, Welsh Govt): Scale and prevalence of sheep scab in Wales (PDF 879 KB)
The presentation will cover the most recent GB and Welsh surveys and thinking on sheep scab occurrence from a Welsh perspective, covering some perceptions about the organic sector, some of the efforts that were and are ongoing in tackling sheep scab in Wales, and reasons for and against government intervention.
Dr Peter Bates (Veterinary Medical Entomology Consultancy): Prevention and control
Sheep scab is a highly deleterious form of allergic dermatitis initiated by faecal antigens of the mite Psoroptes ovis. Scab continues to be a serious problem for conventional and organic producers alike. P.ovis is unable to complete its lifecycle off the host and can remain in an asymptomatic sub-clinical phase for weeks or months following initial exposure. Preventing the introduction of P.ovis, through quarantine and effective fencing/hedging, is therefore the first line of defence. If scab enters a flock it may not be recognised for weeks or even months after its introduction. During this period it can spread throughout the flock. If scab is suspected it is important to have the parasite diagnosed by a vet and the correct treatment applied. Application of the wrong treatment can be costly and prolong the suffering of infested sheep. The range of effective scab treatments available to organic producers is extremely limited and is currently based on the macrocyclic lactones (MLs), all with very long meat withdrawal periods. Overuse of the MLs may also lead to ML resistant gut worms and worse still, ML resistant scab mites. It is essential to investigate new, alternative methods for controlling scab, such as vaccines or biological control agents.
The Cheviot Hills form part of the North North-umberland National Park and are a unique area of outstanding natural beauty. In addition they provide the livelihood for several hundred beef and sheep farmers, many of whom have lived in the area of for a long time. Around the mid to late 1990s sheep scab was becoming an ever increasing problem for a number of sheep farm-ers in North Northumberland and the Scottish Border areas of the Cheviots. The problems posed by this large area for control of sheep scab are discussed with particular reference to the type of farming and other land use within the area. The control strategy is detailed with reference to the organization and co-operation of farmers and the use of a voluntary treatment period. The challenge of ensuring correct product use was achieved by all farmers (including organic) is highlighted.