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The development of quantitative risk-based surveillance strategies for bTB in England & Wales - SE3285

Description
In recent work, a research group led by Kao identified risk-based surveillance strategies for bovine Tuberculosis (bTB) in Scotland, using a combination of statistical models and a simulation model for freedom from infection, to identify a series of possible strategies to reduce the number of regular herd tests for bTB in Scotland. The current proposal will be based on this work where appropriate, but because of the large endemic, 'high risk areas' in England and Wales, we shall also consider different approaches for risk-based surveillance compared to Scotland, that will be guided by the identification of (i) areas where herds are at high risk of breakdown (HRAs), (ii) areas where herds are at a low risk of breakdown (LRAs), and (iii) areas that are perceived as LRAs, but are 'transitional, i.e. at a high risk of becoming HRAs in the near future (TAs). Depending on the type of area, different strategies will be adopted, according to the following criteria:

i) Reduction in testing - directly reduction of the amount of testing done, is a strategy aimed directly at reducing costs. Ideally, this will be a 'dominant' strategy, whereby testing is reduced but with minimal risk of a increase in incidence of breakdowns. This strategy would be most similar to the recommendations for Scotland.
ii) Improvement in ascertainment - this aims to more quickly identify herd breakdowns, most importantly to identify when potential TAs might become HRAs.
iii) Onward risk reduction - this aims partly to identify herd breakdowns more quickly as in (ii) above, however the aim is also to specifically target herds that potentially move many cattle onto other herds, thus increasing the total number of breakdowns in the national herd. This is more likely to be important in HRAs, though onward transmission must also be a consideration in other regions.

We shall adopt a four step approach to this project, using approaches and analyses based on existing work, either published or currently undergoing scientific peer review.
A). Identify HRAs, LRAs and TAs.
B). Develop statistical models to identify risk factors for breakdowns within each type of area.
C) Define risk-based surveillance strategies based on combinations of the criteria (i) to (iii).
D). a within-herd model of transmission will be fit to the available disease notification, demographic and livestock movement data, to identify the potential for these breakdowns to be the source of onward transmission under risk-based strategies in (C); i.e. if and when the new strategy allows some potential breakdowns to persist longer before identification, what is the risk of onward transmission?
E). Based on the best, analytically sound recommendations based on A to D, we shall consult with our partners with policy, farming, and veterinary experience, to determine their feasibility.

We shall therefore provide a comprehensive analysis of all three risk situations (HRA, LRA and TA) where the three aims of testing reduction, improved ascertainment and reduced onward risk will be balanced against the practicality of implementation and relevance to policy requirements.
Objective
O.1). An assessment of the strengths and weaknesses of different components of surveillance, including active and passive (slaughterhouse) surveillance and how to make optimal use of them in herds, or groups of herds, of different risk levels.
O.2). Definitions of subsets of the cattle population or types of herds based on risk of disease. This should include a description of the characteristics or parameters relating to a given population that are important in determining which surveillance regime should be applied to it.
O.3). Outlines of surveillance schemes optimised for different types of risk which can then be targeted with optimised surveillance regimes.
O.4). An estimation of the impact of the surveillance options proposed on the bovine tuberculosis epidemic.
O.5). An assessment of whether annual or biennial herd testing is justified in low incidence areas of England that are currently on 4-yearly testing.

Project Documents
• EVID4 - Final project report : SE3285 Report   (5279k)
Time-Scale and Cost
From: 2012

To: 2014

Cost: £290,857
Contractor / Funded Organisations
University of Glasgow
Keywords
Animal Diseases              
Animal Health              
Control              
Plants and Animals              
Tuberculosis              
Fields of Study
Animal Health