Heterogeneity of pathological prion protein accumulation in the brain of moose ( Alces alces ) from Norway, Sweden and Finland with chronic wasting disease

Prion diseases are a group of neurodegenerative, transmissible, and fatal disorders that affect several animal species. They are characterized by the conformational conversion of the cellular prion protein (PrP C ) into the pathological prion protein (PrP Sc ). In 2016, chronic wasting disease (CWD) gained great importance at European level due to the first disease detection in a wild reindeer ( Rangifer tarandus ) in Norway. The subsequent intensive CWD surveillance launched in cervids resulted in the detection of CWD in moose ( Alces alces ), with 11 cases in Norway, 3 in Finland and 4 in Sweden. These moose cases differ considerably from CWD cases in North American and reindeer in Norway, as PrP Sc was detectable in the brain but not in lymphoid tissues. These facts suggest the occurrence of a new type of CWD. Here, we show some immunohistochemical features that are clearly different from CWD cases in North American and Norwegian reindeer. Further, the different types of PrP Sc deposits found among moose demonstrate strong variations between the cases, supporting the postulation that these cases could carry multiple strains of CWD.