Developing a systems model to identify optimum management approaches for sheep scab control

In environments where poor land quality precludes crop production, livestock represent the primary contribution to agricultural production and food security. Domestic sheep in particular are hardy and well-adapted to marginal land and harsh climates. However, sheep suffer from a wide range of parasites and disease problems, one of the most persistent and damaging of which in the UK is psoroptic mange, known as scab. Scab is caused by infestation by a parasitic mite, Psoroptes ovis. The mites cause a debilitating and destructive clinical disease; there are believed to be over 7,000 outbreaks of scab in UK flocks each year1 costing the UK sheep industry over £8 million per year from mortality, reduced weight gain and the costs of treatment. Despite a number of recent scab education campaigns, there is no evidence that scab prevalence has been reduced. Recent research at the University of Bristol2 has highlighted the risk factors associated with scab outbreaks, quantified the prevalence of the disease and suggested that regional or local scab management programmes may be a more effective use of time and resource than any attempted national eradication programme. However, at present there is considerable confusion about the best approaches to scab management, both in terms of the compounds to apply, when to apply them in relation to seasonal husbandry practices and in terms of farm/region scale effects. The aim of this project therefore, is to develop a systems model which incorporates different farm types and husbandry approaches, incorporating farmer behaviour, to identify optimum management approaches to scab control under specific husbandry regimes.
1Bisdorff, B, Milnes A. & Wall, R. (2006) Prevalence and regional distribution of scab, lice and blowfly strike in sheep in Great Britain. Veterinary Parasitology, 158, 749-752.
2Rose, H., Learmount, J., Taylor, M & Wall, R. (2009) Risk foci for endemic sheep scab in the UK. Veterinary Parasitology, 165, 112-118.