Richard StuttNik Cunniffe
Erik DeSimoneMatt Castle
Chris Gilligan
February 2012
Example results from landscape-scale models◦ SOD in California (precursor to this model)◦ SOD in UK
How the model works◦ Host landscape◦ Environmental conditions◦ Pathogen dispersal
Uses of the model◦ Predictions of spread◦ Effects of control
Key components:◦ Host◦ Environment◦ Pathogen dynamics and dispersal
Expressed as a compartmental model
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
Broadleaved
Young Trees Felled
Coniferous
Identify favourable conditions for P. ramorum◦ moisture ◦ temperature
Parameterise using experimental results
Calculate underlying suitability of locations in the landscape
Statistical used to model future conditions
Dispersal kernel is a statistical description oftransport of inoculum between locations
Implicitly incorporates many mechanisms
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
Survey Positive for P. ramorum
Survey Negative for P. ramorum
Prediction in the absence of control Effect of controls
◦ Felling infected stands◦ Felling infected stands + proactive control
Effect of any delay in implementing control Application to surveying for P. Ramorum
Total Infection
Symptomatic
Symptomatic at time of Survey
Total Infection
Symptomatic
Symptomatic at time of Survey
Total Infection
Symptomatic
Symptomatic at time of Survey
Total Infection
Symptomatic
Symptomatic at time of Survey
Examine region of South Wales
Cull: no delay after survey 6 month delay
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?
Uses:• Currently known outbreaks • Predicted severity of
outbreaks• => Sampling weighting
Survey pattern formed• => sampling from
weightings Map shows a weighting and
a set of survey points (green)
Continue to improve the model Refinement of country wide strategies: Region specific control Effect of non compliance User friendly models
Frank van den Bosch, Stephen Parnell◦ Rothamsted Research
Forestry Commission, FERA◦ (in particular Bruce Rothnie and Keith Walters)
Funding from DEFRA, BBSRC and USDA