Treatment strategies for sheep scab: An economic model of farmer behaviour

•Increased sheep scab prevalence is often blamed on UK farmers not using prophylaxis.•A Game Theory model is developed to assess whether prophylaxis is cost-effective.•Prophylaxis is economical with high regional prevalence and low treatment costs.•Currently, reactive treatment is the most cost-effe...

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Bibliographic Details
Published in:Preventive veterinary medicine 2017-02, Vol.137 (Pt A), p.43-51
Main Authors: Nixon, Emily J., Rose Vineer, Hannah, Wall, Richard
Format: Article
Language:English
Subjects:
Acaricides - economics
Acaricides - therapeutic use
Animal Husbandry - economics
Animal Husbandry - methods
Animal Husbandry - statistics & numerical data
Animals
Cost-Benefit Analysis
Diazinon - economics
Diazinon - therapeutic use
Disease management
Farmer decision-making
Game theory
Macrolides - economics
Macrolides - therapeutic use
Mite Infestations - drug therapy
Mite Infestations - economics
Mite Infestations - prevention & control
Mite Infestations - veterinary
Models, Economic
Prophylaxis
Psoroptes ovis
Psoroptidae
Sheep - parasitology
Sheep Diseases - drug therapy
Sheep Diseases - economics
Sheep Diseases - prevention & control
Sheep scab
United Kingdom
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Summary:•Increased sheep scab prevalence is often blamed on UK farmers not using prophylaxis.•A Game Theory model is developed to assess whether prophylaxis is cost-effective.•Prophylaxis is economical with high regional prevalence and low treatment costs.•Currently, reactive treatment is the most cost-effective strategy for most farmers.•The implications for future policy on scab control are discussed. Ovine psoroptic mange (sheep scab) is a debilitating and damaging condition caused by a hypersensitivity reaction to the faecal material of the parasitic mite Psoroptes ovis. Farmers incur costs from the use of prophylactic acaricides and, if their sheep become infected, they incur the costs of therapeutic treatment plus the economic loss from reduced stock growth, lower reproductive rate, wool loss and hide damage. The unwillingness of farmers to use routine prophylactic treatment has been cited as a primary cause of the growing incidence of sheep scab in the United Kingdom (UK) since the disease was deregulated in 1992. However, if farmers behave rationally from an economic perspective, the optimum strategy that they should adopt will depend on the risk of infection and the relative costs of prophylactic versus therapeutic treatment, plus potential losses. This calculation is also complicated by the fact that the risk of infection is increased if neighbours have scab and reduced if neighbours treat prophylactically. Hence, for any farmer, the risk of infection and optimum approach to treatment is also contingent on the behaviour of neighbours, particularly when common grazing is used. Here, the relative economic costs of different prophylactic treatment strategies are calculated for upland and lowland farmers and a game theory model is used to evaluate the relative costs for a farmer and his/her neighbour under different risk scenarios. The analysis shows that prophylaxis with organophosphate (OP) dipping is a cost effective strategy, but only for upland farmers where the risk of infection is high. In all other circumstances prophylaxis is not cost effective relative to reliance on reactive (therapeutic) treatment. Hence, farmers adopting a reactive treatment policy only, are behaving in an economically rational manner. Prophylaxis and cooperation only become economically rational if the risk of scab infection is considerably higher than the current national average, or the cost of treatment is lower. Should policy makers wish to reduce the national prevalence of
ISSN:0167-5877
1873-1716
DOI:10.1016/j.prevetmed.2016.12.015