Sheep scab

Sheep scab is caused by a microscopic mite called Psoroptes ovis. The mite lives on the skin of the sheep at the base of the fleece and in the ears. The mite, its saliva and its faeces can all cause an allergic reaction in the sheep that causes the sheep to itch. The lifecycle takes 14 days and the population of mites can double every six days¹.

Sheep scab is a serious welfare issue that results in reduced performance including:

• Weight loss
• Fertility
• Poor lamb growth rates

It is a major source of economic loss in affected flocks²:

In 2006, 9% of UK farms were affected by sheep scab³, and 44% of UK farms treated prophylactically for scab⁴.

Sheep scab can be contracted following any contact with live mites, so there are number of ways in which transmission of these live mites can occur:

Sheep to sheep contact: this is the main source of scab being spread, but mites can also contaminate trailers and lorries if infected sheep have been carried in them.

Fencing and hedging: infected wool tags rubbed off onto fence posts, brambles and bushes provide another source of infection to other sheep. 

Equipment: mites can be spread through shared equipment such as shearing, scanning or other tools. 

Animals affected by sheep scab become distressed with symptoms including:

• Wool drop
• Itching, rubbing and scratching with hind feet, or against fence posts/trees
• Soreness, lesions and scabs on the skin

As soon as sheep start rubbing and scratching it is important to consult a vet in order to make an accurate diagnosis. A blood sample or a skin scraping examined under a microscope will confirm if the issue is caused by mange mites or lice. Both can be present at the same time so an accurate diagnosis is required to determine the correct treatment options.

Sheep scab tends to be an autumn and winter issue. Sheep scab mites can survive off the sheep for up to 17 days especially in cold and wet conditions.

Once an accurate diagnosis has been confirmed, best practice is to:

• Plunge dip with an OP product. 
• Quarantine all incoming stock for 3 weeks
• Ensure fencing is sound to prevent straying on and off
• Disinfect livestock trailers after use
• Remove all debris (wool, etc.) from contaminated housing and do not re-stock for at least 3 weeks