Sheep scab is estimated to cost the UK sheep industry £8m a year, with the cost of the disease in a 500-ewe flock estimated to be £6,1502 or £12 per ewe.
If a flock becomes infected with scab it can result in reduced performance, poorer lambing percentage, lower birthweights and reduced lamb sales due to a higher mortality in lambs born to ewes with scab.
The cost of preventing a scab outbreak is in in the region of £1.80 per ewe.
Zoetis vet Dr Dave Armstrong answers some questions on managing sheep scab.
What is sheep scab?
Sheep scab is highly contagious and is caused by an infection with the mite Psoroptes ovis. The female mite lays one or two eggs daily in the fleece of the sheep for about 40 days.
Larval mites hatch from eggs and develop to become adults after two weeks. The mites feed on the surface of the skin and their faeces cause intense irritation, which can cause fits and even deaths in severally infected animals.
What are the symptoms of scab?
In the early stages of flock infestation when mite numbers are low, it can be hard to detect. After several weeks signs of wool loss and itching are noticed.
Other signs include foot stamping, clawing at flanks and biting shoulder, poor body condition and damaged moist red skin. Animals that have been exposed in previous years often show milder clinical signs meaning it is harder to detect.
How do you detect scab in your flock?
The standard way is by microscopic examination of skin scrapings/wool samples to detect the presence of mites.
The second way is a blood test which can detect antibodies to sheep scab which can help identify recently infected flocks.
How is it spread?
The mites are mostly spread by contact with infected sheep. However, handling facilities, transport, shared equipment, trees, bushes, fences and contaminated clothes are also sources of infection.
Mites can survive for up to 17 days off the sheep on contaminated equipment and fences.
Why do I need to protect my sheep?
The signs of scab can have severe welfare and economic implications on a flock. Additionally, in Scotland, the Sheep Scab (Scotland) Order 2010 places a legal obligation on any person who has reason to believe that sheep in their possession or care have sheep scab to notify their local Animal & Plant Health Agency (APHA) office.
What is the incidence of scab?
Outbreaks of scab in the UK have increased 100-fold since its deregulation in 1992, with the highest prevalence in Wales. A survey of Welsh farmers in 2015 reported over 15 per cent with scab outbreaks (154 farms).
In Scotland between 2010-2017 there were 756 premises reported with scab.
How can I prevent scab in my flock?
Maintaining good biosecurity is important.
This includes keeping a closed flock, where possible; having double-fenced perimeters and having an adequate quarantine procedure for new arrivals and returning sheep.
The mites are more active in the winter months, so a sensible time to administer prophylactic treatment is early autumn when worming may also take place.