21-ICRAD: Tackling chronic wasting disease in Europe

Chronic wasting disease (CWD) is a prion disease that affects deer, similar to BSE or "mad cow disease" of cattle. Unlike BSE, there is as yet no evidence that it can spread to humans, but it has become very widespread in wild and farmed deer across North America, with major impacts on population numbers in some areas. In 2016, CWD was found for the first time in Europe, in a wild reindeer in Norway, and since then more cases have been found in reindeer, moose and red deer in Norway and neighbouring countries. The characteristics of the prions from these cases are distinctly different from those found in North America, suggesting that they have not arisen from importation of CWD. There are also major differences between Europe and North America in the species of wild deer, their population sizes and distribution, habitat and management. These differences mean that lessons learned from the experience of CWD in North America do not necessarily apply when planning control of the disease in Europe. This research project will address gaps in our knowledge, with the aim of developing targeted and cost-effective ways to detect CWD and limit its spread within European deer populations. We will use information about CWD cases in Norway and Sweden and deer populations in these countries to develop mathematical tools that help decisions about where to direct disease detection efforts, and predict the spread of the disease, so that control strategies can be devised and tested. These tools can be adapted and applied in other European countries if CWD is found there in future. We will also assess whether there is genetic resistance to CWD among any of the major breeds of wild and farmed deer in Europe, since selective breeding for disease resistance may help in control or prevention of spread. Finally, we will examine the likelihood that European CWD strains could spread to farmed livestock (e.g. sheep, cattle and pigs) or people, by experimental infection of mice that have been genetically altered to mimic the prion susceptibility of each species, as well as alternative laboratory methods. The research consortium working on this project brings together expertise and resources from leading European research groups working on animal and human prion diseases. The outcomes of the project will provide evidence on the potential impacts of CWD in Europe, which will be vital in understanding the risks and planning effective ways to control and prevent adverse effects of the disease on animal, human and environmental health.

Chronic wasting disease (CWD) is a prion disease, similar to scrapie and bovine spongiform encephalopathy (BSE, or "mad cow disease"), which is widespread among wild and captive cervids in North America, with devastating consequences for certain populations. Recent reports of experimental oral transmission of CWD to non-human primates also raise concerns about its zoonotic potential. CWD was first identified in Europe as a novel prion disease in wild reindeer in Norway in 2016, and subsequently found in small numbers of moose and red deer in Norway, Finland and Sweden. Analysis of these cases suggest the presence of a number of distinct prion strains, which differ markedly from those predominant in North America. Differences in European CWD strains and deer species/populations from those in North America mean that further research is urgently needed to develop risk assessments and control strategies specific to the European context. This project will integrate research on the epidemiology and population dynamics of the disease in affected countries, with experimental approaches to study host/pathogen interactions relevant to disease transmission in wildlife, livestock and people. Information on CWD cases and cervid population data in Norway and Sweden will be used to develop models to evaluate surveillance strategies, predict CWD spread in affected populations, and indicate potential for transmission through contacts with semidomesticated reindeer and livestock. PRNP gene sequencing of European cervids will allow identification of novel variants that may be associated with resistance to CWD and could be used in selective breeding for disease control. The potential for transmission of European CWD isolates to sheep, cattle, pigs and humans will be assessed using in vitro and in vivo models. Project outcomes will support risk assessments of potential impacts of CWD on animal/human health, and lead to improved and cost-effective surveillance and control strategies.