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Analysis and design of scrapie surveillance strategies in Great Britain - SE0243

Several surveillance sources are targeting the occurrence of scrapie in Great Britain. The statutory reporting, from 1993, and two forms of active sources since 2002: the abattoir and the fallen stock surveys. Furthermore, two postal surveys were conducted following recommendations from the Spongiform Encephalopathy Advisory Committee (SEAC). None of the sources, by its own, allow the unbiased estimation of the frequency of scrapie. Logistics limitations, varying testing schemes and changes in the general and regulatory context have also limited comparisons in time and space.

To achieve Defra’s aims, the reduction of the prevalence of scrapie by 40% in 2010, and, eventually, the eradication of the disease, comprehensive and repeatable estimates of the occurrence of the disease are required. There is a need to provide an estimate of the occurrence of scrapie that is accurate and comprehensive and that allows meaningful comparisons in time. Reliable and prompt identification of changes, in its broadest terms, in the occurrence of scrapie are needed. New data (i.e. genotype distribution), different sampling protocols (i.e. “dead in transit”) and testing techniques (i.e. BioRad vs. Western Blot), new events (the recent confirmation of the atypical scrapie cases) and a better knowledge of putative risk factors at the animal and holding level must be taken onboard in future modelling. Furthermore, in a context of scarce and competitive resources, there is a need to approach the problem efficiently. Cost-effective surveillance streams are required together with the study of alternative sampling and data collection schemes.

The overall aim of our research is to provide estimates of the frequency of ‘scrapie’ in GB sheep and to inform modifications to existing surveillance activities. In more detail, we aim to integrate the estimates already available from the different surveillance sources to improve our understanding of the status of the GB sheep population with respect to scrapie. We will extend our approach to include disease and infection at both levels: individual animals and holdings.

In addition, our results will inform the most cost-effective sampling strategies that will result in consistent estimates of the frequency of ‘scrapie’ year to year. These estimates are a keystone in the process of eradication of the disease as they will allow progresses to be monitored. This will improve the ongoing assessment of the efficacy of control measures and the ability of the system to detect disease (sensitivity) during the process towards eradication.
Project Documents
• Final Report : Analysis and design of scrapie surveillance strategies in Great Britain   (5387k)
• Final Report : Analysis and design of scrapie surveillance strategies in Great Britain   (586k)
Time-Scale and Cost
From: 2005

To: 2008

Cost: £561,851
Contractor / Funded Organisations
Veterinary Laboratories Agency, Institute for Animal Health (BBSRC), Royal Veterinary College
Animal Health              
Plants and Animals              
Fields of Study
Animal Health