Sheep Scab Mite

Sheep scab is an acute or chronic form of allergic dermatitis caused by the faeces of sheep scab mites (Psoroptes ovis).

Sheep scab is an acute or chronic form of allergic dermatitis caused by the faeces of sheep scab mites (Psoroptes ovis). The mites are just about visible to the naked eye and can only remain viable off the host (sheep) for 15-17 days. The sheep is the only host where the mites can complete their lifecycle, though there is evidence that they can remain viable on cattle. The lifecycle takes 14 days and the population of mites can double every six days.

Sheep scab is a major source of economic loss in affected flocks and is a serious threat to sheep welfare. Infestations can be very debilitating with significant loss of condition, secondary infections, hypothermia and eventually death. Sheep scab is a notifiable disease in Scotland.

It can be contracted via any contact with live mites, so there are number of transmission risks.

  • Sheep to sheep contact is the main source of disease spread, but contaminated trailers and lorries are also a risk.
  • The mites can live in wool tags for up to 16 days, making rubbing posts and areas, as well as brambles and bushes, a source of infection to other sheep.
  • Shearing, scanning or other shared equipment, including greasy overalls and moccasins can also spread the mites.

Sheep scab is mainly a winter disease with most cases occurring between September and April, although can occur at any time of the year, particularly on full fleeced animals such as lambs and the ‘ridges’ of longer fleece on poorly shorn sheep.

Clinical Signs

During the early stages of sheep scab, mite numbers are low and infestations are not obvious, with animal often appearing clinically normal. Sheep may be restless, rubbing against fence posts, have soiled and stained areas of wool, toss their heads or have deranged or tags of fleece. At these early stages, sheep can look perfectly normal and can unknowingly be introduced to a flock. In fact, up to 60% of a flock can be infected before any clinical signs are seen, which can take several months.

Later stages of infestation see high mite numbers and lesions spread as the mites move to the edge of the lesions to find new food sources. Rubbing and head tossing becomes more and more excessive, areas of wool loss may appear, often with open, bleeding wounds. Sheep rapidly lose condition and serious cases will start fitting.

More in SCOPS TECHNICAL MANUAL, Chapter 4.4. 

Downloads

Download the SCOPS 'Have you got all the facts you need to protect your flock from sheep scab?' guide.

Related Organisations

Connected Content

National Sheep Association (NSA) is an organisation that represents the views and interests of sheep producers throughout the UK.

The livestock industry is an integral part of the agricultural sector, encompassing various aspects of animal husbandry and production. It plays an important role in global food security and supports the livelihoods of millions of people worldwide.

Sheep scab is an infection caused by the mite Psoroptes ovis, which spends its entire lifecycle on the sheep. Unfortunately, it can cause significant health and welfare issues within flocks as it is highly contagious. Each year, the Welsh sheep industry loses £5.86m between treatments and loss of production. It also implies serious economic and welfare losses at farm level from reduced stock growth, lower reproductive rate, wool loss and skin damage.  Tackling scab is a challenge as sources of infections are not limited to one farm. Risks of infection are either increased by the presence of scabs within neighbouring flocks or reduced if those flocks are prophylactically treated. 

Sheep were one of the first farmed animals, reared for thousands of years for meat and milk.

Animal health is integral to the sustainability, profitability, and ethical considerations of livestock farming. It involves a combination of preventative measures, good management practices, and veterinary care to ensure that animals are raised in a manner that is both economically viable and environmentally responsible while prioritizing their well-being and public health.

If you’re responsible for a farm animal you must make sure that you care for it properly. (DEFRA)