Nicholas Haley, DVM and PhD 4:17 p.m. MST January 22, 2016
Perhaps no issue is as controversial in the hunting community right now as Chronic Wasting Disease. There’s constant finger-pointing and a lot of theories about how it will change hunting forever for the worse. But fortunately, emerging scientific research suggests that CWD doesn’t have to be the scourge that many fear.
Last year, a herd at an Iowa ranch was depopulated after one of the animals tested positive for CWD, as is standard U.S. Department of Agriculture protocol. However, the situation took years to resolve as the ranch owner fought for a more equitable solution. As such, CWD naturally spread among the animals.
This provided a unique opportunity for testing of the animals, since depopulation normally occurs relatively quickly. After testing and euthanizing the entire herd, sadly a large percentage were identified as CWD positive. The silver lining was that 20 percent were negative, and we are currently looking at a genetic link to resistance in these animals.
If we can further characterize this resistance in deer, that’s very promising. As CWD spreads — and it will, since you can’t stop free-ranging deer from moving around — then the deer that are more genetically susceptible to the disease will die off at higher rates than those that are less genetically susceptible. The net result will be a hardier population of deer that is more resistant to CWD. With farmed deer, there’s the potential to select for this resistance faster than nature herself could.
Other research has pushed the genetic resistance theory. The Wyoming Department of Fish and Game and the University of Wyoming jointly conducted a study, published last year, indicating that if CWD hit elk populations in the state’s northeastern region, the populations would bounce back.
It’s possible that genetic selection has already been occurring in areas such as Wyoming and Colorado. CWD was first found in a free-ranging deer in Colorado in 1985. Yet researchers in Colorado have noted that CWD does not appear to have had any significant effect on the deer population size. Similarly, CWD was first found in elk in Colorado in 1981, and elk numbers have grown since then.
The Iowa herd didn’t only provide a boost to genetics research. The samples collected from the animals also contributed to efforts to develop an antemortem, or live-animal, test. Currently, CWD can only be detected by using the tissue of deceased animals, making it difficult to monitor. A breakthrough here would make managing CWD much easier and more precise.
Elsewhere, new research has looked at ways through which CWD can be transmitted. A study published this year found that CWD could be transmitted by plant matter. Researchers demonstrated that wheat grass roots and leaves could take up prions (infected proteins that make up CWD and similar diseases) if exposed to infected urine or feces. When this same plant matter was fed to hamsters, the animals became infected.
If CWD can be transmitted by plants, then that raises a whole host of questions about the transportation of hay and other animal feed.
Taken together, what does this all mean for hunters?
It means CWD will continue to spread, and there’s not much we can do about it at the moment. Political efforts to restrict or ban deer and elk farming are pointless, because CWD has long been in the wild, where we can’t get rid of it due to the resilient nature of prions. On the contrary, farmed cervids may represent controlled populations where, as we’ve shown, advancements in CWD detection and prevention can be made quickly. These advancements not only benefit farmed deer and elk, but wild populations as well.
In the short term, we may see a slight dip in some deer populations as the disease spreads. But in the long run, we should expect deer populations to be hardy as genes that provide resistance to CWD increase in prevalence.
As for research, live-animal tests have decent accuracy — though not yet perfect. Expect them to get better.
The news stories about CWD popping up here and there won’t stop. But progress is being made against CWD, even if it’s slow.
Dr. Haley is an assistant professor with the Department of Microbiology and Immunology at Midwestern University’s Glendale, Ariz., campus.
0 Comments
Leave a reply
You must be logged in to post a comment.