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Modelling the spread, control and detection of Ramorum Disease
Cambridge Richard StuttUniversity Nik Cunniffe
Erik DeSimoneMatt CastleChris Gilligan
Rothamsted Stephen ParnellResearchFrank van den Bosch
May 2012
Model must integrate◦ Location of hosts◦ Environmental drivers◦ Pathogen dispersal
Compartmental model
Model – Spatial Stochastic Model
250m x 250m resolution
Combine data on Larch Rhododendron Vaccinium NIWT (other tree hosts)
Weight host types by sporulation/susceptibility
Model – Host Landscape
Pathogen responds totemperature/moisture
Model underlying suitability for each location
Statistical climate model then used to predict future fluctuations about this
Model – Environment
Dispersal kernel describes pathogen spread
Implicitly incorporates many mechanisms
Model – Dispersal
Positive Negative
Spread in the absence of control
Effect of extent of control◦ Felling infected stands◦ Felling infected stands + proactive control
Surveying for P. Ramorum on heathland
Results – Typical Applications
Continuous model improvement (data driven)
Region specific control
Effect of non compliance
Transition strategies
User friendly models
Current and Future Work
Forestry Commission◦ Bruce Rothnie◦ Joan Webber
FERA◦ Keith Walters◦ Phil Jennings◦ Judith Turner◦ Kate Somerwill
Funding from DEFRA, BBSRC and USDA
Acknowledgements
Susceptible hosts in the landscape are divided into a metapopulation at a chosen resolution (250m)
UK Sudden Oak death landscape assembled from:◦ National Inventory of Woodland Trees (NIWT)◦ Forestry Commission commercial Larch data◦ Maximum Entropy suitability models for Rhododendron and
Vaccinium (FERA/JNCC)
Different hosts have different weightings for sporulation and susceptibility
Model - Host
Identify favourable conditions for P. ramorum◦ moisture ◦ temperature
Parameterise using experimental results
Model - Environment
Rela
tive S
poru
lati
on
Temperature
Fit model using historic spread data
Used Maximum Likelihood to assess goodness of fit
Predicted probability of infection by 2010 given starting conditions in 2004
Model - Validation
Survey Positive for P. ramorum
Survey Negative for P. ramorum
Key Questions When Surveying for Disease:◦ Where is the disease likely to be?◦ Where is it likely to be most severe and spread
most rapidly?◦ How to optimise the sampling?
Sampling Strategies