The Annual Cost of Sheep Scab is around £8.3m in Great Britain
Sheep scab is a major threat to the sheep industry, impacting on growth rates and causing serious welfare implications.
Its prevalence has increased in the past 20 years following its declassification as a notifiable disease in England and Wales in the 1990s (although it has been notifiable since 2010 in Scotland). It is a legal requirement to treat infected and in-contact animals, which are then unable to be moved or sold until their withdrawal period is up.
Symptoms
Most sheep farmers will have experienced sheep scab within their flock, especially in areas of high sheep density. It is caused by the mite Psoroptes ovis.
Sheep experience intense itchiness causing wool loss and crusting skin, leading to reduced appetites, decreasing body condition and immunosuppression, along with a reduction of growth rates in lambs.
The mites thrive on fully fleeced animals, and itching is usually seen at housing in the autumn and winter. However, we are now regularly diagnosing scab in late summer as well.
Adult mites live on the surface of the skin, where their faeces cause intense allergic reactions. This often happens 40-50 days after infection as the mite population builds up.
Before considering treatments, it is important to get a diagnosis, as other parasites can cause similar problems, but need different action.
Spread
Sheep scab is spread by contact with live mites, so understanding their ability to live both on and off the host allows the selection of appropriate control and treatment options.
The mites can live off sheep for up to 17 days on wood and wool, often on barbed wire and fence posts used as scratching areas.
These provide a common transmission pathway between flocks, alongside close contact between sheep.
Other common methods of transmission include contact at the market, mites on livestock trailers, shearing equipment and trailers – and even on contaminated clothing.
Diagnosis
There are several ways to diagnose sheep scab. The most common is a skin scrape, with mites detected under microscopy or by potassium hydroxide (KOH) digest.
A positive result to either of these tests confirms a current infestation and all in-contact sheep should be treated.
Normally you don’t see signs until 40-50 days after infection, which is when the scrape is useful. You can’t do it before any lesions are present as you don’t know where to look for the mites.
Treatment
Treatment options are currently organophosphate (OP) plunge dipping or injection with macrocyclic lactones (MLs).
When deciding between injectable or dipping treatment consider whether you need to target internal parasites or only external. Selection may depend on integration into the flock’s current worming strategy.
If it is not possible to use an OP dip, it is vital to choose the correct ML, get the job right the first time.
Why Zermex?
- Flexibility no need to treat the whole flock on the same day.
- Flock Management treated sheep can be returned to the same pasture.
- Scab Control Satisfaction Guarantee 2
The Best Value
Treat ewes and lambs as a single injection for long acting scab control or prevention as an alternative to routine dipping.
All treatment options should be discussed with your territory manager.