Transmission, Strain Diversity, and Zoonotic Potential of Chronic Wasting Disease

Abstract

Chronic wasting disease (CWD) is a prion disease affecting several species of captive and free-ranging cervids. In the past few decades, CWD has been spreading uncontrollably, mostly in North America, resulting in a high increase of CWD incidence but also a substantially higher number of geographical regions affected. The massive increase in CWD poses risks at several levels, including contamination of the environment, transmission to animals cohabiting with cervids, and more importantly, a putative transmission to humans. In this review, I will describe the mechanisms and routes responsible for the efficient transmission of CWD, the strain diversity of natural CWD, its spillover and zoonotic potential and strategies to minimize the CWD threat.

Keywords: PMCA; chronic wasting disease; prion diseases; prion strains; prions; spillover potential; zoonotic potential.

Figure 1

Schematic representation of the different hypotheses to explain the CWD origin. Although the origin of CWD is largely unknown, various hypotheses have been proposed, including transmission from a scrapie-infected sheep, a mutation in the Prnp gene (illustrated as a star in the left panel) and a spontaneous misfolding of PrP^C into PrP^Sc.

Figure 2

Animal species susceptible or at risk to be infected with CWD. Various animals cohabit with cervid, including livestock, rodents, scavengers, carnivores, domestic animals, and humans. Several studies of experimental infection of animals by CWD have shown that sheep, goats, cattle, ferrets, raccoons, and rodents can be infected with CWD [88,89,90,91,92,93,94].

Figure 3

An overview of various strategies to minimize CWD spreading. Various alternative approaches have been proposed to decrease the risk of further CWD spreading, including detailed surveillance, selective breeding of animals harboring rare polymorphisms partially resistant to CWD, development of a highly efficient test for CWD detection, selective culling of infected animals, prion decontamination, and development of a treatment for CWD.