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A review of chronic wasting disease in North America
with implications for Europe
&David R. Edmunds
Received: 29 January 2018 /Revised: 28 January 2019 /Accepted: 10 February 2019 /Published online: 21 February 2019
#Springer-Verlag GmbH Germany, part of Springer Nature 2019
Cervids are keystone species in ecosystems and are associated with enormous cultural and economic value. Chronic wasting
disease (CWD) is a fatal prion disease spreading in North American cervid populations. The 2016 emergence of CWD in Europe
makes it urgent to understand the basics of CWD and to assess the extent to which current CWD knowledge is transferable to
Europe. CWD is difficult to detect in the early stages due to very low prevalence and slow growth rates. The negative population
effect of CWD is mainly due to increased female adult mortality, as infected individuals continue to reproduce. It may take
decades before CWD leads to population declines. The population dynamics of mule deer are affected more by CWD than those
of white-tailed deer, which in turn are more affected than those of elk, and depending on other factors limiting the populations.
Species- and population-specific differences in dynamical consequences are linked to the balance among the rates of transmis-
sion, incubation period (linked to the prion protein gene, PRNP), and reproductive rates. This make it difficult to predict effects of
CWD in Europe with other cervids, but the dynamic impact may be marked to cervid populations over the long term. The process
of spillover across the species barrier is not well understood. Occasional spillover to moose without an apparent epizootic
suggests specific conditions can limit CWD. Frequency-dependent transmission or weak density–dependent transmission makes
it difficult to control CWD using density reductions through harvest and/or culling. CWD is difficult to eradicate once it becomes
endemic, and it calls for immediate management actions. These actions involve extensive culling, fencing, and ceasing of wildlife
feeding and are likely to cause significant controversy.
Keywords Frequency-d ependent ver sus density -dependent transmissi on .Directand environmentaltransmissionroutes .Spatially
targeted harvesting .Extermination and fallowing .Salt licks and supplemental feeding .Genetics and pathology .Epizootiology
and population dynamics
The first case of chronic wasting disease (CWD) in Europe
was diagnosed in March 2016 in a female reindeer (Rangifer
tarandus) in the Nordfjella mountains, Norway (Benestad
et al. 2016). Since then, several more CWD-infected reindeer
from the same population were detected by testing during the
2016 and 2017 hunting seasons (Viljugrein et al. 2019).
Hence, we have the first reported outbreak of CWD in
Europe. CWD was first documented in a captive mule deer
(Odocoileus hemionus) in 1967 in Colorado, USA (Williams
and Young 1980), and it appeared in wild mule deer in 1981
(Williams and Young 1992; Spraker et al. 1997;Milleretal.
2000). CWD in the wild has since spread to 25 states and,
through sales of farmed elk, has been introduced to two
Canadian provinces and to South Korea (Uehlinger et al.
2016); however, the origin of CWD in Norway remains un-
known (Benestad et al. 2016).
It is important to realize that although CWD was first iden-
tified among wild deer in 1981, it is still spreading to new
areas and continuing to increase in prevalence in most, if not
all, endemic areas. Evidence of declining populations in en-
demic areas is recently reported for white-tailed deer
(Odocoileus virginianus) (Edmunds et al. 2016) and mule deer
Centre for Ecological and Evolutionary Synthesis (CEES),
Department of Biosciences, University of Oslo, P.O. Box 1066,
Blindern, NO-0316 Oslo, Norway
Natural Resource Ecology Laboratory, Colorado State University,
Fort Collins, CO 80523, USA
European Journal of Wildlife Research (2019) 65: 26