Chronic wasting disease

Abstract

Until recently, chronic wasting disease of cervids, the only prion disease affecting wildlife, was believed to be geographically concentrated to Colorado and Wyoming within the United States. However, increased surveillance has unveiled several additional pockets of CWD-infected deer and elk in 12 additional states and 2 Canadian provinces. Deer and elk with CWD have extensive aggregates of PrP(Sc) not only in the central nervous system, but also in peripheral lymphoid tissues, skeletal muscle, and other organs, perhaps influencing prion shedding. Indeed, CWD is transmitted efficiently among animals by horizontal routes, although the mechanism of spread is unknown. Genetic polymorphisms in the Prnp gene may affect CWD susceptibility, particularly at codon 225 (S/F) in deer and codon 132 (M/L) in elk. Since CWD infects free-ranging animals and is efficiently spread, disease management will be a challenge.

Figure 1

Immunohistochemistry of mule deer brain and lymphoid tissue using anti-PrP antibody F99/97.6.1 [67]. PrP^Sc deposits in the brainstem and tonsil from a CWD-infected mule deer (panels b, d), but not in an uninfected deer (panels a, c).

Figure 2

Map depicting the CWD cases detected in North America. (Map kindly provided by the National Wildlife Health Center).

Figure 3

Superposition of the mean NMR structures of the polypeptide segment 125–229 (C) and 165–172 (D) in ePrP(121–230) (red) and mPrP(121–230) (blue). A spline function was drawn through the C positions. The radius of the cylindrical rods representing the polypeptide chains is proportional to the mean backbone displacement per residue (XX), as evaluated after superposition for best fit of the atoms N, C, and C′ in the 20 energy-minimized conformers used to represent the NMR structures [43, 68]. Figure provided by Simone Hornemann. Data published in reference [43, 68].

Figure 4

Mule deer with clinical signs of CWD including hypersalivation, a lowered head, emaciation, and a dry, rough hair coat (panel a). A clinically normal control mule deer is shown for comparison (panel b).