Sunday, November 19, 2023

Chronic Wasting Disease


The CWD agent is shed from infected hosts in urine, feces, saliva, blood, and antler velvet (Figure 3) and can occur in preclinical and clinically affected animals (). CWD prions are also present nearly ubiquitously throughout a diseased host, including skeletal muscle; cardiac muscle; fat; a wide range of glands, organs, and peripheral nervous tissue; and in the highest concentrations in the CNS (,). Thus, CWD prions will enter the environment through shedding from diseased and deaths animals (carcasses). Although quantification of infectious CWD titers in excreta and tissue is challenging, the total titer shed from an infected animal during its lifespan may be approximately equal to the total titer contained in an infected carcass ().

Environmental transmission of the CWD agent was reported in studies demonstrating that an infected deer carcass left in a pasture for 2 years could transmit the agent to immunologically naive deer (). Exposure of naive deer to pasture previously inhabited by an infected deer also led to CWD transmission, as did cohabitation of naive and infected deer (). Naive deer exposed to water, feed buckets, and bedding used by CWD-infected deer contracted the disease ().   Source
One of the signs that deer hunters use to determine if there are bucks in the neighborhood is to look for scrapes or scrape-lines. That is where bucks paw up the ground, pee on it and poop on it and then paw it up some more. This is how they tell the girls in the neighborhood that they are studly dudes, kind of like an 8th grader dousing himself with Axe Aftershave.

Less well known is that above the scrape there is almost always a "licking stick" that the deer rub their preorbital scent glands on and lick and sniff at. It is the equivalent of dogs peeing on the fire hydrant. The so-called licking stick is used year-round. My gut feel is that licking sticks are a major cause of the rapid horizontal transmission of CWD.

CWD positive areas at the granularity of Townships

Looking at Eaton County. Eaton Rapids area circled in Cyan

The Michigan DNR is pouring a lot of money into collecting deer heads to monitor the spread of Chronic Wasting Disease in deer. It would be a whole lot cheaper to collect licking sticks and they would have samples from a larger sample size than an individual head.

I suspect that licking sticks could be identified by using UV light. Saliva and other protein-rich body fluids glow under black-light.

Just an idea.


  1. There you go using logic and rational thought. You know that the bureaucrats can't stand that.

  2. You are assuming that bureaucrats actually want to solve problems. There's no funding in that.

  3. I wonder which government lab CWD was developed in.---ken

    1. Colorado State University(CSU) Ft. Collins Colorado.

  4. I think, and this should be read with very wide error bars, a lot of the issue comes down to the current testing tech. My understanding is that there are a bunch of different CWD testing methods that occupy various points on cost vs sensitivity vs false positive rate scales.

    The tests that can detect it at very low concentrations also have higher false positive rates and cost more. So, while some people are researching stuff like water based detection (I think based on streams/outflows, but you could also check under scrapes as well), the tech vs cost vs risk issue might edge away from checking licking sticks. Essentially, you could end up with an extremely costly (in terms of public panic, actual dollars spent on testing program and follow up testing costs) program that might not give you more data than broader testing of harvested deer.

    However, the broader point (if I may summarize) of "a lot of the researchers don't really understand deer-in-the-wild" I think is probably true. I have a casual acquaintance that did some CWD research in grad school (I don't know what she does now), and despite having worked in a lab on CWD she knew absolutely nothing about deer behavior, hunting or anything that would enable her to understand such a suggestion.

    This (and it's 1 person, so possibly plenty of people in the labs aren't so myopic) makes me believe the research on testing methods is accidentally guided into techy/nerdy solutions (trying to track CWD by sampling streams) vs simply tracking licking sticks, scrapes or (crazy idea) simply testing all the road kill deer.

    Here's a discussion of some research on the water based testing:

    Personally, I'm getting pretty good at cutting lymph nodes out of deer. Hardly even had to watch a refresher video this year!

  5. Ohh, since I can't edit 3 things I forgot:

    1. The DNR is operating under an "avoid false positives as much as possible" methodology. AFAIK lymph node testing is the most accurate testing in terms of avoiding (as much as possible) false positives b/c the tissue naturally concentrates the prions.

    2. If we really wanted to limit CWD (which I desperately do) simply ban all deer/cervid farms. They are responsible for 99.99999999% of CWD introductions into states, they are breeding grounds for CWD, they are (largely) run by rule-bending nutters that mean they are very hard to regulate and are a TINY industry compared to hunting. If we had banned them 20 years ago, CWD wouldn't be an issue today. If we ban them today, it will be a limited issue going forward. Whatever we (normal hunters/people) do, it's like trying to clean your floor while someone has a pair of muddy boots still on and is walking around. Constant escapes, constant rule violations, and based on research in pens/installations actually eliminating CWD from a farm is functionally impossible. Once a farm has a CWD positive test result it should be instantly closed, burned to the ground and the entire area fenced off for at least 30 years (and kept fenced off).

    It's like John Von Neumann's approach to China. If you say ban them tomorrow, I say why not today. If you say a 5pm, why not noon?

    3: My understanding is there is research showing (fairly strongly hinting at least) that the dose makes the poison. Technically 1 prior can infect, but in practice you need pretty sustained contact/close quarters to spread it. It's possible licking sticks stay under the concentrations to be an important vector. I don't know that this has been studied at all and a brief google wasn't helpful.

  6. To Spartan's point above, I wonder how much (if any) money is being spent on working on better/new development methods. I cannot imagine this has a lot of money directed towards it and certainly no medical device companies or testing labs really delving into the issue except for research or graduate work.

    Note to hunting organizations: Offer to fund some researchers on the subject. It might be the only way to get modern technology and methods on the case.

    1. Bovine Spongiform Encephalitis is considered a prion-based disease (there are doubters) and it crossed over into humans to become Jacob-Crutchsomething disease or Rachel Madcow disease.

      There is a concern that CWD might cross over into humans. If it does, the first case will open the floodgates for research dollars. Anybody with a head-start will be well position to capture some of those dollars.

    2. That is already a major concern in dairy country here in Southern Minnesota: The possible cross contamination by deer saliva due to deer getting into the silage bags and bunkers prior to it being fed to the dairy cows, as well as being in the pastures. Our DNR has extended seasons, and extra tags to try to control the population in our area. Still too many long legged rats!

    3. Wish we could send you some of those packs of wolves we have here in da UP. They really clobbered the deer herd here. Deer hunting season here has been the worse anybody has ever seen.---ken

  7. There is also evidence that plants which deer feed upon take up the prions and spread it.

  8. Not good news for hunters and venison eaters...


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