Sheep Lice and Scab

Lice are small, pale red/brown flat insects (approx. 3-4mm long) feeding on skin debris and hair, living within the centimetre of the wool closest to the skin.

The most common louse in sheep is the biting or chewing louse Bovicola ovis. Lice can be found anywhere on the sheep and do not produce a definite scab lesion. Lice populations are influenced by body condition – the lower the body condition score the higher the population of lice.

The main method of transfer is animal to animal contact. Lice are, therefore, a particular problem in housed sheep, although it is not a building problem. As lice can live off the animal for 16-17 days, it is possible for a farmer to bring an infestation onto their farm through brought in stock, clothing or livestock transport.

Lice can cause intense irritation, restlessness and scratching as infested sheep rub themselves. The fleece appears rough and pulled, with numerous loose strands of wool. Sheep can bite and nibble at the fleece.

Lice are primarily an autumn and winter parasite as they do not like the dry bright conditions seen in summer.

As soon as sheep start rubbing and scratching it is important to consult a vet in order to make an accurate diagnosis and advise best treatment, especially as sheep can have mixed infections of sheep scab and chewing lice.

Best practice is to:

• 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

Crovect™ Pour On is an easy to use, synthetic pyrethroid pour-on which kills biting lice

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 days.¹

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.

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.

Best practice is to:

• 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

Where sheep scab is confirmed, plunge dipping in an OP product is the treatment of choice. Where this is not possible, a single intramuscular injection of Dectomax® Injection will kill the mange mites that cause scab.