Animal Health & Welfare

Sheep scab is a disease caused by a parasitic mite - Psoroptes ovis - which lives on the skin surface. The feeding activities of the mite cause irritation and distress, which can result in stunting or severe loss of condition, loss of fleece and death - especially in lambs.

Sheep Scab (Scotland) Order 2010

The Scottish Sheep Scab Industry Working Group was set up in 2007 to work in partnership with Government to consider the development of legislation to control and reduce the incidence of sheep scab in Scotland. SAC participated in this group. The Sheep Scab (Scotland) order 2010 was produced following extensive consultation with that group.

Primary responsibility for controlling sheep scab still falls to the owner or keeper of sheep and the new Order is designed to concentrate attention on those farmers who have failed to treat their animals.

The Order places a legal obligation on any person who knows or suspects that sheep or carcases in their possession or in their charge of having sheep scab to notify that fact to the Divisional Veterinary Manager (DVM) as soon as possible.

If an inspector suspects that sheep scab exists, and owners have failed to either treat or slaughter the affected sheep, the Order contains provisions for a notice to be served by an Inspector, requiring the owner/keeper to arrange and pay for a veterinary enquiry to either confirm or rule out the disease. 

The Sheep Scab (Scotland) Order 2010 courtesy of the Scottish Government website

A summary of the signs, preventative measures and treatment of scab is given below.

Signs

Signs of itchiness may be attributable to sheep scab due to Psoroptes ovis or lice infestation with Boviclova ovis. Identifying which of these organisms is responsible may require laboratory tests, but is critical in applying an effective treatment (see the press release from Defra regarding diagnosis on the right).

• Sheep will scratch, rub, nibble and kick at affected areas and large proportions of fleece may be lost.
• The skin becomes hardened and often develops raw patches that are open to infection from bacteria.
• Loss of condition due to secondary bacterial infection and lack of rest through constant irritation occurs.
• In advanced cases death may occur

Prevention and Treatment

SAC has produced a technical note and checklist on treating scab, which can be accessed on the right. Further information on the law relating to sheep scab can be found under 'Sheep Scab (Scotland) Order' above.

Control of sheep scab depends on coordinated plunge dipping or endectocide injection involving all flocks in a geographically defined area and taking into account the survival of the scab mite off the host, the time taken to kill mites and the persistence of the product used. Coordinated action between neighbours and effective biosecurity are therefore essential.

• Minimise direct contact with other flocks by paying attention to fence maintenance and double fencing if possible.
• Quarantine and treat for scab in all incoming sheep for at least 3 weeks before mixing with the resident stock.
• Consider that mites can survive in the environment. Remember that livestock lorries and shearing equipment can also spread scab.

If sheep scab is confirmed on a holding, a notice may be served requiring the keeper to treat the sheep within a specified period. The person on whom the notice is served should then either, a) treat the sheep with an approved product, or b) ensure that sheep are slaughtered. Strict movement restrictions are enforced where scab is confirmed.

Organophosphate (OP) plunge dips are effective and broad spectrum, no resistance has been reported and a single dip will protect against re-infestation.

Endectocides (injectable products) control both internal and external parasites. Injection sites and dose rates may vary depending on the product so it is crucial to follow the manufacturers instructions carefully. Some provide poor protection against re-infestation.

Further information from Defra on the prevention and treatment of scab, in addition to other skin infestations of sheep can be found under 'related internet links' to the right.