Cooperative Fish and Wildlife Research Units Program: Wisconsin Wildlife
Education, Research and Technical Assistance for Managing Our Natural Resources

The goal of this proposal is to use computer simulation modeling to evaluate a number of objectives related to CWD spatial epizootiology and management. Researchers will use an integrated approach by combining simulation modeling and maximum likelihood methods to evaluate alternative disease transmission models with CWD prevalence data collected in Wisconsin and Illinois during 2002-2008. Researchers have currently developed and evaluated simulation models that estimate CWD transmission rates and deer demographics using frequency- (FD) and density-dependent (DD) transmission. They will address the following objectives: 1) Extend the models to evaluate non-linear transmission that represents more realistic contact structures and transmission rates that are intermediate to FD and DD transmission, using maximum likelihood to estimate transmission parameters from CWD infection data collected in Wisconsin and Illinois. Researchers will evaluate how these transmission modes affect CWD epizootiology, deer demographics, and management responses based on different culling strategies. Because little is known about the relative importance of direct and indirect transmission on CWD dynamics they will also consider the implications of environmental sources contributing different levels (e.g., 0%, 25%, and 50%) of CWD transmission. 2) Use simulation models, current CWD prevalence, and historical deer abundance to develop maximum likelihood estimates of the time when CWD was introduced (or time disease has been present) at selected locations in Wisconsin and Illinois. Based on the suspected disease foci in both areas researchers will use regression analysis to determine the relationship between distance from suspected introduction locations and time disease has been present. This analysis will provide an estimate of the rate of CWD spread across the landscape (distance/time relationship). 3) Utilize spatially explicit simulation models with published deer dispersal parameters to evaluate the relative potential for CWD spread between uniform deer habitats (e.g., south-central WI) and fragmented deer habitats (e.g., IL-WI area). Researchers will use spatially explicit models to consider a three-zoned ring buffer for CWD management. These zones will include a core infected area, a surrounding buffer with lower prevalence, and a third concentric buffer without disease. They will simulate differential harvest strategies and buffer sizes to evaluate different management and surveillance strategies. Use the spatial simulation model to evaluate alternative surveillance strategies for detecting and monitoring CWD at the landscape level. Researchers will evaluate trade-offs between surveillance based on clinical animals (so called targeted surveillance), hunter shot animals (random surveillance), and from both sources combined. They will also evaluate sample sizes and times required to detect CWD in new areas or in areas adjacent to outbreaks. Based on the results above investigators will evaluate alternative surveillance strategies related to increases in CWD prevalence through time and with requirements for early detection of disease to achieve successful disease management.