In 2016, classical contagious Chronic Wasting Disease (CWD) was detected for the first time in Europe in wild reindeer (Rangifer tarandus) in Norway. One reindeer population of around 2,000 animals was culled, but the disease later reappeared in another, larger and less confined population, where two cases have been detected so far.
Host factors such as genetic susceptibility can strongly influence how epidemics develop. In this study, Mysterud and Osnes with a team involving UIO, NMBU, and our partners SVA and NVI, explored epidemic trajectories using a digital twin of the Norwegian reindeer population where CWD is assumed to persist. They tested different assumptions about how host genetics affect disease dynamics—looking at differences in susceptibility, disease duration, and the level of prion shedding during infection.
The findings show that genetic effects can lead to qualitatively different epidemic outcomes. For example, when susceptibility is genetically modulated, the epidemic shows a sharp peak followed by a decline. But when genetics also increase disease duration, the peak occurs at a similar time, yet prevalence stabilizes instead of declining. Sensitivity analyses suggest that the results depend strongly on parameter assumptions, highlighting the need for empirical studies to better predict the trajectory of CWD.
Photo: Olav Strand / Norwegian Institute for Nature Research (NINA)
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