Farmers who don’t treat their animals to avoid sheep scab are, in some scenarios, making the most economically sensible decision, research from the University of Bristol suggests.

sheep scab
Severe case of sheep scab caused by Psoroptes mites, by Alan R Walker (CC BY-SA 3.0).

Before 1992, farmers throughout the UK were required by law to treat all their sheep to prevent the infectious condition, which is caused by a tiny parasitic mite. At that time, around 40 outbreaks occurred per year.

Change in law

Consequently, once compulsory treatment was removed, the number of scab outbreaks rose dramatically and around 5,000 to 10,000 outbreaks occur each year, costing the UK sheep industry at least £10 million annually.

Despite many industry initiatives, the failure to reduce scab incidence is often blamed on farmers unwilling to use routine preventive treatments.

However, new research funded by the Biotechnology and Biological Sciences Research Council has shown many of these farmers are being blamed unfairly.

Looking closer

mite infestation
Photograph of parasitic mite infestation of sheep, by Alan R Walker (CC BY-SA 3.0).

In the study, published in Preventive Veterinary Medicine, losses and treatment costs were analysed along with the risks of scab to show whether it is financially better for a farmer to treat to prevent scab either:

  1. before any sheep are infected
  2. only if the flock contracts scab

Specific solutions

According to researchers, analysis suggested under current conditions it is only cost-effective for farmers to use preventive treatments in areas where the scab risk is highest – Scotland, northern England and Wales – as well as where high-risk grazing strategies (particularly common grazing) are used.

For farmers in other areas, meanwhile, it is more cost-effective in the long run to only pay to treat if and when their flock gets scab.

The work concluded there is not always one blanket disease control strategy for all farmers – instead, tailoring strategies to specific regions or farms is preferred.



  1. Nixon E, Vineer HR and Wall R (2017). Treatment strategies for sheep scab: an economic model of farmer behaviour, Preventive Veterinary Medicine 137(Part A): 43-51.
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