In this part 3 of 3 about chronic wasting disease, let us talk about working to control CWD.
Eradicating CWD from North America doesn’t seem feasible given its extensive distribution and other epidemiological attributes. Faced with dim prospects for eradication, some affected jurisdictions now seem to have abandoned any further consideration of disease management and some have effectively dismantled surveillance and monitoring. Considering numerous wildlife conservation needs and ever-dwindling resources, this approach should be reconsidered, and wildlife managers are strongly encouraged to redouble efforts to collectively develop sustained approaches for CWD surveillance, monitoring and control.
In recent years, evidence from some control attempts suggests that combinations of intensive deer removal around case clusters, as well as more sustained reduction of the affected population, may offer some measure of disease suppression. A sustained, localized culling program underway since 2003 has stabilized occurrence in northern Illinois whitetails as compared to the increasing trends in southern Wisconsin, where disease control largely was suspended in 2007.
One of the most common flaws in CWD control efforts to date has been the initial underestimation of the affected area. The outcome then gives the appearance that the control attempt has failed when, in fact, the approach was biologically sound, but the application was either too small (spatially) or too short-lived.
It follows that acquiring reliable distribution and infection rate data in the planning and early implementation stages may improve the effectiveness of future CWD control efforts. Consequently, wildlife managers are encouraged to set realistic disease-control objectives and to use an adaptive management approach that incorporates future field data to define objectives and strategies.
In addition to adopting approaches for stabilizing or suppressing CWD outbreaks, wildlife managers are encouraged to consider how recent trends in cervid management may be contributing to disease establishment. Modeling suggests harvest-based control of CWD may be most effective when focused on male deer, perhaps because infection rates among adult male deer tend to be higher than among adult females. On the other hand, harvest strategies intended to increase the percentage of male cervids or the percentage of older class males, could inadvertently facilitate CWD persistence.
Control efforts undoubtedly will be difficult to obtain support for, particularly when disease control measures will negatively impact or conflict with commercial cervid enclosures and/or hunting by the general public. The human dimensions of managing wildlife diseases in general — and CWD, in particular — present a substantial challenge for those determining the management objectives and actions.
The lessons learned over the past five decades relate to how wildlife and animal health professionals should (and probably should not) approach the control of CWD. However, recent insights and modest strides seem to offer a path forward, and adaptive approaches for containing CWD within limited geographic areas and for reducing infection and transmission rates deserve further attention.
James L. Cummins is executive director of Wildlife Mississippi, a nonprofit, conservation organization.
