CWD Update: State of the Science

[Benbrown]

A long, but understandable, read on the state of the science, new research directions, possible new management actions and the curious occurrence of outlier infected populations.

 

https://www.nytimes.com/2017/06/26/science/chronic-wasting-disease-deer-elk-prions.html?module=WatchingPortal&region=c-column-middle-span-region&pgType=Homepage&action=click&mediaId=thumb_square&state=standard&contentPlacement=2&version=internal&contentCollection=www.nytimes.com&contentId=https%3A%2F%2Fwww.nytimes.com%2F2017%2F06%2F26%2Fscience%2Fchronic-wasting-disease-deer-elk-prions.html&eventName=Watching-article-click&_r=0

[forepaw]

So the theory that the misfolded prions may be occurring spontaneously may mean it did not originate with Scrapie from domestic livestock - which also could mean it might not behave the same way as BSE in terms of transmission to humans?

 

Lots of questions regarding origin (was it a chance gene?) and natural resistance of exposed animals that do not develop symptoms. I didn't see any mention that it has been around forever, like some animal illnesses (ebola), so what triggered it over the past few decades? And until the Norway outbreak, only in N. America?

 

forepaw

[Benbrown]

Short answer is that nobody knows for sure exactly how it originated and we may never know. The fact that it first appeared in deer pens at CSU in Fort Collins, which were built on ground that had been experimental sheep pens for dozens of years, suggests that the prions that cause scrapie may have somehow transformed and became infectious to deer. However, as the article said, new research shows that the prions of Cervids (deer, elk, moose and their close relatives) are very susceptible to the spontaneous deformation that could make them infectious.

 

It has been suggested that the disease may have existed in nature for a long time at a very low infection rate and was only diagnosed when it began appearing in penned deer in an experimental facility where the the animals were observed almost every day for a long period of time. The fact that the prions are apparently virtually indestructible and remain infectious in the soil for a long time may be the reason for the seeming pyramiding rate of infection in wild cervids. With respect to the outback in Norway, spontaneous deformation seems to be a most unlikely explanation right now. Whitetail deer have been introduced in and are hunted in several Scandinavian countries in northern Europe. Those deer were probably taken from commercial deer breeding operations or hunting preserves here in the states, both of which have become hotbeds of CWD infection.

[tmcguire]

Interesting read. If prescribed burns do curb the spread of the disease, it would mean the "Smoky bear affect" has even more consequences than just huge wildfires every few years. This article goes into more details, but it talks about how prior to the 1900s smaller fires every 5-10 years were the norm and served to clear all the underbrush and create healthier forests. http://www.npr.org/2012/08/23/159373691/how-the-smokey-bear-effect-led-to-raging-wildfires

Also, not to derail the thread, but have there been any confirmed CWD cases in Arizona? Was hunting the San Carlos for Turkey this past spring and watched two elk walk into a tank all the way up to their chins and just stand there with just their heads exposed and drink and drink and drink. Honestly forgot about the whole ordeal until reading this thread. The animals looked healthy, but seemed like odd behavior considering it was 40 degrees outside. (I know back East that was how you could tell a whitetail had CWD, when the disease progressed enough they would normally just drown in a pond or lake trying to drink as much water as they could)