Contagious and always-fatal neurodegenerative disorder

In a scattershot pattern that now extends from coast to coast, continental US states have been announcing new hotspots of chronic wasting disease (CWD).

The contagious and always-fatal neurodegenerative disorder infects the cervid family that includes deer, elk, moose and, in higher latitudes, reindeer. There is no vaccine or treatment.

Described by scientists as a slow-motion disaster in the making, the infection’s presence in the wild began quietly, with a few free-ranging deer in Colorado and Wyoming in 1981. 

However, it has now reached wild and domestic game animal herds in 36 US states as well as parts of Canada, wild and domestic reindeer in Scandinavia and farmed deer and elk in South Korea.

In the media, CWD is often called zombie deer disease due to its symptoms, which include drooling, emaciation, disorientation, a vacant staring gaze and a lack of fear of people. As concerns about spillover to humans or other species grow, however, the moniker [zombie deer disease] has irritated many scientists.

CWD is not caused by bacteria or a virus, but by “prions”: abnormal, transmissible pathogenic agents that are difficult to destroy. Prions have demonstrated an ability to remain activated in soils for many years, infecting animals that come in contact with contaminated areas where they have been shed via urination, defecation, saliva and decomposition when an animal dies. Analysis by the US Geological Survey has shown that numerous carcasses of hunted animals, many probably contaminated with CWD, are transported across state lines, accelerating the scope of prion dispersal.

[Tom] Roffe and others say the best defence is having healthy landscapes where unnatural feeding of wildlife is unnecessary and where predators are not eliminated but allowed to carry out their role of eliminating sick animals.