Predicting disease spread from host movement data: Chronic wasting disease in North America as a case study

Rare long-distance movements can increase the spatial spread of invasive species and shifts in species ranges. For wildlife disease spread, however, seasonal migrations may only matter if they lead to transmission to individuals using different seasonal ranges, and the importance of juvenile dispersal depends on whether those juveniles are infected before they disperse. High-resolution animal movement data are increasing, but it is unclear how to leverage these data to improve predictions of future disease spread particularly in regions without pre-existing movement data. We predicted the speed of chronic wasting disease (CWD) spread based on movement metrics of mule deer (Odocoileus hemionus) and white-tailed deer (Odocoileus virginianus) and compared our predictions to observed spreading rates in North America from 2005 to 2022. We hypothesized that CWD should spread faster in regions with long-distance migratory mule deer, but this hypothesis was only partially supported. Observed rates of CWD spread were faster in western epicentres with more mobile mule deer than in epicentres with only white-tailed deer (14-18 km/year compared with 5-7 km/year, respectively). However, the observed speed of CWD spread did not align well with migration distances. Deer movements in the Canadian Prairie Provinces were far shorter than those in Colorado and Wyoming, yet Canadian Prairie Provinces had faster CWD spread, and, much of that spread was in open prairies where deer movements tend to be along riverine corridors rather than the longer elevational migrations in more montane regions. Generally, our predicted rates of CWD spread from three different models were slower than the observed rates regardless of whether the model included dispersal or migration. Understanding these discrepancies is needed before high-resolution animal movement data can be used to predict broad-scale patterns of disease invasion. Anthropogenic movements likely explain longer distance movements of CWD across North America, but it remains unclear whether human-mediated movements or alternative analytical methods and deer movement metrics can explain the faster than predicted local CWD spread.