NR AXJN
AU Birch,C.; Chikukwa,A.; del Rio Vilas,V.
TI A Cellular Automata Approach to Modelling the Transmission of Scrapie by Sheep Movements Between Flocks
QU International Conference - Prion 2007 (26.-28.9.2007) Edinburgh International Conference Centre, Edinburgh, Scotland, UK - Book of Abstracts: Epidemiology, Risk Assessment and Transmission P04.91
IA http://www.prion2007.com/pdf/Prion Book of Abstracts.pdf
PT Konferenz-Poster
AB
Control measures against scrapie are usually applied to whole flocks, so the most important process in the transmission of scrapie is movement of sheep between flocks. Whole life movements of ewes are of especial interest, because of the long incubation time of scrapie. Cellular automata provide an opportunity to model the transmission of scrapie by sheep movements, including interactions with environmental factors such as farm altitude and the effects of variations in sheep density. They also promote the combination of dynamic spatial modelling with geospatial technologies. This model involved three main areas of technological development:
1. Development of methods to identify birth and death holdings of ewes sampled for scrapie. Animal movement databases allowed the tracing of c. 17000 samples taken from fallen ewes to their birth holdings. Consistent with expert knowledge, over 80% of ewes died where they were born, so scrapie transmission depends on the minority of ewes that are mobile. Similar tracing methods have also been applied to much larger numbers of scrapie samples from abattoir surveys. 2. Generation of simple cellular automata movement models for sheep in the UK from the data on ewes that moved. These included observed contrasts between movements to upland and lowland holdings. Such contrasts can influence the potential distribution of scrapie. 3. Application of recently developed cartogram methods to deal with uneven sheep distributions by transforming between regular equal area projection maps and a space in which sheep are evenly distributed. The cartogram was divided into a grid consisting of 80000 cells, each of which represented a single holding. This allowed inclusion of environmental factors (e.g. hills and coastlines), while keeping model mechanics very simple. This work has demonstrated the potential for simple simulations to recreate the broad characteristics of scrapie epidemics.
AD C. Birch, A. Chikukwa, V. del Rio Vilas, Veterinary Laboratories Agency, CERA, UK
SP englisch
PO Schottland