Sheep Scab – what you need to know
Sheep scab has been present in the UK for many years, but recent data suggests that infection rates are on the rise. It is therefore crucial that we as farmers, vets and producers understand how to reduce the risk of introducing the disease into flocks; how to spot clinical signs; and how to effectively treat infected sheep.
What is Sheep Scab?
Sheep scab is caused by the sheep mite Psoroptes ovis which lives on the skin of affected sheep.
Sheep scab feed on skin debris and sheep scab faeces causes intense irritation, leading to wool loss, rubbing on fence posts, soiled or stained areas of wool, and restlessness. Disease progression of Sheep Scab leads to skin thickening and scabs, self-mutilation and weight loss as prolonged agitation prevents affected sheep from eating.
What is the Sheep Scab problem?
It is estimated that there are about 8-10,000 outbreaks of sheep scab in the UK every year with some flocks persistently infected in areas of high sheep scab. Although traditionally seen as mainly a winter disease, we are increasingly seeing infection throughout the year. Current legislation means that flock owners in England, Wales and Northern Ireland are under no obligation to report a diagnosis of sheep scab; however, the disease is notifiable in Scotland. Therefore, there are no accurate figures for sheep scab infection rates in the UK.
Although more advanced cases of sheep scab can be easily spotted through clinical signs, initial infection may result in small lesions of less than 1cm in diameter and so cases can be easily missed. This, in addition to the lack of reporting of positive sheep scab flocks, means that buyers are at real risk of purchasing sheep from scab infected flocks without knowing.
Once sheep scab is within a flock, the mites move from sheep to sheep via direct contact. However, scab mites may also survive on gate posts, shearing equipment, clothing and in the environment for up to 17 days. This means that scab mites can easily move between flocks and groups of sheep within an infected flock, or via straying neighbouring sheep.
I think I’ve got sheep scab in my flock – what can I do?
The stigma attached to a positive diagnosis of sheep scab may prevent some farmers seeking veterinary help. However, diagnosis is key as similar clinical signs may occur following infection with other ectoparasites – knowing what disease you are targeting is crucial to understanding which treatment to use.
Diagnosis can be confirmed by observation of the sheep scab mites down a microscope following a skin scrape from suspect cases, taken by your vet – the mites cannot be seen with the naked eye. Sheep may also be blood sampled for evidence of exposure to the mite: positive results occur two weeks after infection.
Sheep Scab Treatment and Prevention control options:
Timely treatment of sheep scab cases is crucial: positive cases are a welfare issue due to the intense irritation associated with the infection.
I buy in sheep – what can I do?
Treatment or testing for sheep scab should be included in quarantine procedures on arrival. Quarantine bought in sheep for at least 28 days.
- Test bought in sheep for their exposure to sheep scab 14 days after arrival on farm using the blood test (ELISA) AND/OR
- Treat bought in sheep for scab by either plunge dipping or using moxidectin-based injectable.
I’ve heard about plunge sheep dipping – what’s it all about?
Plunge dipping sheep for ectoparasite control has been around for a long time, and many may remember the period of compulsory sheep dipping in the 1970s and 80s. Following increasing awareness of anthelmintic resistance and reports of sheep scab resistance to injectable products there has been renewed interest in the role of plunge dipping for sheep scab.
Synergy Farm Health in collaboration with Neil Fell have launched a sheep plunge dipping service. The aim is to dip sheep in a calm, stress-free manner, optimising sheep welfare whilst maintaining operator safety.
The mobile plunge dipping system runs on a large lorry, with a small group of sheep loaded into a wire pen which is then fully submerged into the sheep dip. The wire pen of sheep are submerged (for a minute in total), fully submerged for a second, two or three times during the minute, to ensure full ingress through the fleece. Sheep are grouped in even sizes to ensure that they are calm throughout. The system is hydraulic, remotely operated to ensure a safe and effective method of dipping sheep whilst maximising human health. Due to the calm nature of the process, ewes can also be dipped close to lambing.
Unlike injectable products, plunge sheep dipping does not target internal parasites thereby avoiding unnecessary treatment of roundworms and reducing the risk of developing wormer resistance. The dip also provides longer-term cover for other ectoparasites such as blow fly, ticks, lice and keds. We have several clients using the service during the summer months to provide protection against fly strike, or tick cover in known high-risk pastures. Others are using the service prior to sale to ensure their customers are getting sheep in tip-top condition. Sheep must have 1cm cover of wool to be dipped. Unfortunately, plunge dipping is not suitable to sheep producing milk for human consumption or in organic flocks. Find out more here.
Our Mobile Plunge Sheep dipping service covers the south west of England and Wales. For more details please contact reception on 01935 83682 or email VetTechReception@synergyfarmhealth.com
Written by Nicky Ogden
