Sheep scab appears to be rife in the north east of Scotland at the moment, as shown by recent figures from the Animal Health and Veterinary Laboratories Agency (AHVLA). With Scotland introducing sheep scab as a notifiable disease in 2010, data collected since shows that almost half of the 76 cases reported in Scotland this year were in Aberdeenshire. Other regions such as Perthshire, Ayrshire and Lanarkshire also had a proportionately higher incidence of sheep scab cases. With the fast approaching winter months being the typical season for sheep scab, there are concerns about further spread.
The Psoroptes ovis mites that are responsible for the disease feed on the skin surface and it is hypersensitivity to their secretions that cause the intense itching which characterises infection. The highly contagious nature of the condition can lead to significant production losses on sheep farming enterprises and has huge welfare implications. Fleece damage and interrupted feeding patterns adversely affecting live weight gains are the most significant sources of loss to farmers. Severely affected animals may display seizure activity and infection can even result in death.
The AHVLA have produced a map illustrating the number of cases reported in all regions of Scotland which allow hotspots and disease free areas to be easily identified. The north-east of Scotland, where the greatest geographical concentration of cases seems to be, is a region typically associated with growing and finishing lambs. Concerns about appropriate biosecurity for bought in animals on these farms have been raised as a result. Current advice recommends that bought in animals for which treatment history is unknown should be dosed for scab upon arrival to the new premises. A single injection of doramectin (Dectomax®) is effective for the treatment and prophylaxis of Psoroptes mite infestations. It is important to treat all new animals, even if not displaying signs of the disease, as some infections are asymptomatic. The new sheep should then be quarantined with no contact to neighbouring untreated sheep, in one place for at least 17 days as mites can survive for this period in the environment.
The responsibility of reporting disease falls to anyone who suspects a case. Farmers can be reassured that diagnosis is government funded but must also be aware that transport restrictions will be imposed until the disease has been successfully treated. Full details of the legislation can be found at www.legislation.gov.uk/ssi/2010/419/contents/made.
Countries such as New Zealand have successfully achieved eradication of Psoroptes and the fact that authorities in Scotland have put sheep scab firmly on the agenda places them one step closer to being able to boast the same. With these alarming trends emerging in Scotland already this year and the mites responsible traditionally being more active in the winter months, increased vigilance by everyone is imperative to prevent dramatic spread.
Dectomax® 1% w/v solution for injection contains 10mg/ml Doramectin, Legal category POM-VPS
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