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Clinical Examination Protocol to Detect Atypical and Classical Scrapie in Sheep
Published on: January 19, 2014
A Bayesian framework to assess the potential for controlling classical scrapie in sheep flocks using a live
Aiko Gryspeirt1, Simon Gubbins
1The Pirbright Institute, Ash Road, Pirbright, Surrey GU24 0NF, UK.
Epidemics
|September 12, 2013
Summary
Current scrapie control relies on removing at-risk animals. While live diagnostic tests show promise for targeted approaches, current flock schemes are more effective in controlling classical scrapie outbreaks in sheep.
Area of Science:
- Veterinary epidemiology
- Prion disease research
- Animal health management
Background:
- Classical scrapie control strategies primarily target animals at risk, not necessarily infected ones.
- Advances in diagnostic technologies suggest potential for more precise, live-testing-based scrapie management.
- Existing control methods may not fully leverage the potential of rapid diagnostic assays.
Purpose of the Study:
- To evaluate the effectiveness of live diagnostic tests for classical scrapie control in sheep flocks.
- To compare the impact of recto-anal mucosa-associated lymphatic tissue (RAMALT) biopsies and blood-based assays against current control strategies.
- To model the dynamics of scrapie spread and assess intervention efficacy using a stochastic, agent-based approach.
Main Methods:
- Development of a stochastic, age- and prion protein (PrP) genotype-structured model for scrapie dynamics in sheep.
- Bayesian framework for parameter estimation, integrating diverse datasets and quantifying uncertainty.
- Simulation of control strategies including removal of clinical cases, live diagnostic testing (RAMALT and blood assays), and the Compulsory Scrapie Flocks Scheme (CSFS).
Main Results:
- In small flocks, removing clinical cases was sufficient; live testing offered no significant advantage.
- In medium to large flocks, widespread live testing reduced outbreak size but not always duration compared to clinical case removal.
- The current Compulsory Scrapie Flocks Scheme (CSFS) demonstrated superior reduction in both outbreak size and duration compared to clinical case removal and live testing strategies.
Conclusions:
- Implementing live diagnostic tests for classical scrapie offers limited additional benefit over existing methods in small flocks.
- For larger flocks, while live testing can reduce outbreak size, the CSFS remains the most effective strategy currently.
- Under the study's assumptions, there is minimal advantage in adopting control strategies that rely solely on live diagnostic tests for classical scrapie.
