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Sheep Lice and Scab

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:

  • 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


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:

  • Weight loss
  • Fertility
  • Poor lamb growth rates

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:

  • 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.

References: 1. SCOPS 2. Stubbings, L ., (Sept, 2007). The prevalence and cost of sheep scab. Presentation to the Sheep Veterinary Society 3. Bisdorff, B., Wall, R., Milnes, A., (2006). Prevalence and regional distribution of scab, lice and blowfly strike in Great Britain. Veterinary Record,158(22), 749-52. 4. Bisdorff, B., Wall, R., (2008). Control and management of sheep mange and pediculosis in Great Britain. Veterinary Parasitology, 155(12), 120-6 CLiK™ EXTRA 65 mg/ml Pour-On Suspension for sheep contains dicyclanil and is indicated for the prevention of blowfly strike on sheep caused by Lucilia sericata or Wohlfahrtia magnifica. CLiK™ Pour-On for sheep contains 5% (w/v) dicyclanil and is indicated for the prevention of blowfly strike due to Lucilia sericata or Wohlfahrtia magnifica on sheep CLiKZiN™ Pour-On Suspension for Sheep contains the active ingredient dicyclanil and is indicated for the prevention of blowfly strike on sheep due to Lucilia sericata. Crovect™ Pour-On for sheep contains 1.25% (w/v) cypermethrin (cis:trans/80:20). For the treatment and control of headflies, tick infestation with a persistent efficacy of 10 weeks (the majority of ticks killed within 3 hours) and treatment of biting lice in sheep. Also for the prevention and treatment of blowfly strike in sheep. Legal category for all: POM-VPS Dectomax™ 10 mg/ml Solution for Injection for Cattle and Sheep contains Doramectin and is indicated for treatment and control of gastrointestinal roundworms, lungworms, eyeworms, warbles, lice and mange mites in cattle. Legal category: POM-VPS. Information regarding the side effects, precautions, warnings and contra-indications can be found in product packaging and leaflets; further information can also be found in the Summary of Product Characteristics. CLiK™ EXTRA, CLiK™, CLiKZiN™, Crovect™, Dectomax™, FleeceBind™, Elanco™ and the diagonal bar™ logo are trademarks of Elanco or its affiliates. Use medicines responsibly (www.noah.co.uk/responsible). Advice should be sought from the prescriber prior to use. © 2021 Elanco or its affiliates. PM-UK-21-0216