Lice and scab - caused by mange mites - cause disease and production losses in sheep and the financial impact to the farmer can be severe if an effective treatment programme is not implemented without delay. As irritation/pruritus is the main clinical sign in early cases of both louse and mite infestations 1, it is critical to get an accurate early diagnosis in order to then implement a targeted, effective treatment plan, and minimise production losses.
What are the differences between lice and mange mites?Lice
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:
Crovect™ Pour On is an easy to use, synthetic pyrethroid pour-on which kills biting lice
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 days.1
Sheep scab is a serious welfare issue that results in reduced performance including:
It is a major source of economic loss in affected flocks2:
Source: Stubbings, L ., (Sept, 2007). The prevalence and cost of sheep scab. Presentation to the Sheep Veterinary Society
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:
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:
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.
