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Sheep Scab

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The National Animal Disease Information Service (NADIS) was formed in 1995 to promote animal health and welfare through better disease control and prevention. NADIS recognises this is best achieved by active veterinary health planning. Key to improving health is disease surveillance and veterinary based, animal health Knowledge Transfer, delivered to farmers by their veterinary surgeon. To help farmers and smallholders, Nadis regularly emails out seasonal information and webinars, and publishes a monthly Parasite Forecast for farmers and livestock keepers, based on detailed Met Office data. The Parasite Forecast outlines the parasitic challenge facing cattle and sheep in the different UK regions. This month’s webinar focuses on Parasite Control – Planning Ahead, Liver Fluke Risk, Chronic Fluke Disease in Sheep and Cattle and Lice in sheep and cattle. Below is a recent alert sent out by NADIS with regard to Sheep Scab.


Sheep scab is caused by the mite Psoroptes ovis; cattle are not affected.  Mites are most commonly transmitted by direct contact with infested sheep, but can survive off the sheep for 17 days and so can be transmitted indirectly on posts, fences, vehicles etc. 

Sheep scab can be introduced into a flock by

  • Carrier sheep, including purchased animals
  • Sheep returning from grazing
  • Contact with neighbouring sheep/common fences.

Economic importance

Failure to recognise and treat sheep scab promptly, or improper treatment, can incur serious economic loss due to:

  • Increased feed costs to compensate for rapid loss of body condition 
  • Low birth weights and higher mortality occur in lambs born to ewes which suffered sheep scab during pregnancy. 

Clinical signs

Animals are often seen at different stages of the disease within affected flocks. On a flock basis, sheep scab is characterised by

  • Intense itching
  • Repeated rubbing of the shoulders and flanks along the ground or against fences
  • Foot stamping, clawing at the flanks, and biting the shoulders 
  • Tufts of wool are characteristically seen on fences and hedges
  • As the disease progresses, wool is lost and the skin becomes thickened and covered with thick scabs.

Handling of sheep with extensive scab lesions may precipitate seizure behaviour. New wool growth occurs as the disease regresses and lesions heal.

Clinical Images Gallery

  1. Sheep scab infestations causes rapid weight loss. Increased feeding to restore body condition proves expensive.

  1. Sheep scab during late pregnancy leads to lower lamb birth weights.

  1. Sheep scab is characterised by intense itching and biting the shoulders.

  1. Sheep scab is characterised by intense itching.

  1. Wool along the length of this fence is not normal and warrants immediate investigation.

  1. As the disease progresses, wool is lost and the skin becomes thickened and covered with scabs.

  1. Areas of wool loss with thickened skin become covered with scabs.

  1. Animals are often seen at different stages of the disease within affected flocks.

  1. Psoroptes ovis mite under the microscope.


Differential diagnoses

Sheep scab must be differentiated from louse infestation and necessitates veterinary examination.


The diagnosis of sheep scab is based on the clinical signs and veterinary confirmation of Psoroptes ovis mites in superficial scrapings collected from the periphery of exudative lesions. 

Confirmation of Psoroptes ovis infestation is essential to ensure a correct diagnosis and treatment.


Treatment should be discussed with your veterinary surgeon.

Plunge dipping in organophosphorus sheep dips

Plunge dips containing dimpylate (active substance) kill scab mites within 24 hours and afford residual protection for several weeks.  Plunge dipping also treats any lice, blowflies, and ticks present on the host.   

Systemic endectocide injections

Two subcutaneous injections, seven days apart, of 200 µg/kg ivermectin, or a single intramuscular injection of doramectin at a dose rate of 300 µg/kg provide effective control of sheep scab. While a single injection of doramectin achieves some persistence, this may occasionally be insufficient to provide protection against re-infection for the whole 17 day period during which the scab mite can survive off the sheep.  A single subcutaneous injection of moxidectin at a dose rate of 200 µg/kg provides residual protection against sheep scab for at least 28 days, although the UK data sheet recommends two injections 10 days apart for the treatment of disease outbreaks. Treated sheep must be kept isolated in a clean area for 7-14 days after treatment depending upon the product used.

Prevention, biosecurity and control

Sheep scab control will form an important part of your veterinary flock health plan.

Some important components of such control include:

  • Maintain a closed flock wherever possible
  • Maintain secure double-fenced perimeters where they contact other fields containing sheep
  • Treat all purchased sheep upon arrival on farm and quarantine in a clean area for at least two weeks
  • Investigate all cases of pruritus and fleece loss.

Welfare implications

Sheep scab is a serious animal welfare concern.  


You can find a more detailed account od sheep scab on the NADIS website at Alternatively, make sure you receive all their informative bulletins by signing up for their regular email newsletters, which can also be downloaded as pdfs. The information will shortly be available via a free app too. Visit to register. You can follow NADIS on Twitter at @NADIS_UK.


Posted in: Sheep

About the Author:

Paul Melnyczuk is editor of Home Farmer, and together with Ruth Tott is the founder of the company. His Ukrainian father and Austrian mother came over in the 1950s, and he was raised near Accrington (of Stanley fame) in Lancashire. With a degree in European Literature and a year spent living in Sweden, and a further 2 years in the Sudan, his background is rich and varied.

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