Back to Stories & News

November 20, 2018 –  As hunting season begins, Dr. Diehl discusses chronic wasting disease with Dr. Dave Edmunds, a research scientist at Colorado State University’s Natural Resource Ecology Laboratory. This is a fatal, neurological disease that affects members of the deer family, which  was first detected in 1967. Dr. Edmunds covers many aspects about the disease, including its history and biology, and his Morris Animal Foundation-funded research to better understand it.

00:17 Dr. Kelly Diehl: Hi, I'm Dr. Kelly Diehl, Interim Vice President of Scientific Programs at Morris Animal Foundation. And if this is your first time joining us, our podcast features funded researchers, as well as our staff members discussing their work in advancing animal health. But before we start, I'd like to begin with a little history about us for those who are new to the Foundation. The Foundation was actually the brainchild of Dr. Mark Morris Sr., who was a pioneer really in small animal medicine. Dr. Morris used royalties from the development of his specially formulated diets which we're now all familiar with as Hill's Prescription Diets, to provide the seed money for what eventually evolved into Morris Animal Foundation. When Dr. Morris created the Foundation back in 1948, he had a vision of supporting research projects that would directly benefit the health of animals. And 70 years later, here we are, still going strong. We funded over 2,600 studies and invested more than $120 million now in studies benefiting dogs, cats, horses, llamas, alpacas and wildlife.

01:34 DD: For example, many of you may not realize that the Foundation played a big role in, for example, the early studies of canine parvovirus, the development of the first feline leukemia virus vaccine, we were instrumental in developing the diagnostic tests we use for combined immuno-deficiency and lavender foal syndrome obviously in horses. We'd studied most recently the effects of the Deepwater Horizon oil spill on a variety of different aquatic species. We've also funded assisted reproductive techniques that helped reestablish the endangered Przewalski's horse, and we did some of the initial studies that led to the development of the PennHIP evaluation method for predicting osteoarthritis in dogs, which many of us in practice have used. Education also was a part of Dr. Morris' vision for the Foundation, and we're continuing that founding principle through this podcast series. And our hope is we can provide interesting new information in a fun and informal atmosphere.

02:45 DD: Okay. So, let's jump in today's podcast. In the studio with me today, is Dr. Dave Edmunds. Dave received his Bachelor’s degree in wildlife sciences from Virginia Tech, and he got his Master's and PhD in wildlife disease ecology from the University of Wyoming. Dave's current position is as a research scientist in the Natural Resource Ecology Laboratory at Colorado State University. And several years ago, we granted Dave some funding to look at chronic wasting disease, which is the subject of today's podcast. So welcome, Dave, and I'm going to jump in now with our first question which is, what is chronic wasting disease?

03:38 Dr. Dave Edmunds: So chronic wasting disease is a neurological disease of members of the deer family, or more specifically, it's a transmissible spongiform encephalopathy or a TSE, also known as a prion disease of the deer family, and it's an always fatal disease that takes... Chronic being it takes a long time for clinical science to emerge and for death to occur in the animal.

04:01 DD: Okay. So, I have a question. When and where did this disease, like when did people first recognize this?

04:10 DE: So, it was first detected in 1967 in a captive mule deer herd in Fort Collins, Colorado. And at the time, it was a nutritional study and nobody knew what... That it was a TSE of course, and in fact, they thought maybe it was had something to do with the study that was ongoing. And then in 1978, Dr. Beth Williams who discovered the disease, was a graduate student at Colorado State University, and she recognized that microscopically, the brains of these deer looked eerily similar to sheep that died of scrapie, which is another TSE or prion disease. And so, at that point, it was determined that this was actually a prion disease and a newly discovered disease.

04:55 DD: Okay. So, I have a question for you, and I know this is a... It's a weird entity, a prion. Can you tell us briefly what a prion is?

05:06 DE: So yeah, so we all have prions; prions are just a normal cellular protein that's found on the surface of cells, but when they become misshapen, when they're exposed to these infectious prions, they change shape and they become infectious themselves and they cause the disease. And primarily, in neurological tissues, so the spinal cord, nerves, and in the brain of animals.

05:35 DD: Okay.

05:37 DE: They're highly resistant to degradation, they're really hard to break down, they bind to soil, and they're even taken up by plants, and that's one of the ways that we think that deer can spread the disease from individual to individual is it goes from the saliva or the urine or the feces into the ground, it gets bound to these... To the soil, and then the plants actually take them up and they could be consumed by the next deer that comes along.

06:05 DD: Okay. So, you mentioned scrapie, what other diseases might our audience recognize as prion diseases? What diseases in other words are similar to this?

06:18 DE: Probably the most famous one is what's known as mad cow disease or bovine spongiform encephalopathy that was really popular in the press back in the late 90s, early 2000s. Humans also have prion diseases, a disease called kuru is a prion disease and also Creutzfeldt-Jakob disease or CJD. That's probably the most common prion disease in humans.

06:42 DD: Okay, so I think you're right. Everybody's heard of mad cow disease. How well known is chronic wasting disease do you think? Or have you seen a change in awareness since you first started looking at it several years ago?

07:00 DE: I have. I think when I first started on what became my graduate project in the early 2000s, I think people were really interested in CWD. And what I've noticed with wildlife diseases in general is they kind of go in waves of popularity. And CWD became rather unpopular for a while. Not very many people were concerned about it, especially in Wyoming where it’s been known to be around since the 1990s. And then research shows that it’s probably been around since the 1970s or 1960s. And so people became less concerned about it. And then recently, I've noticed that it's become much more popular in the press. Hunters are more concerned about it. And then especially in new states where it's found such as in Michigan. Hunters in new states where it's newly discovered are extremely concerned about it. So it kind of depends on how long it's been around and then how much popular press it gets.

07:56 DD: Right. You mentioned the spread of the disease and again hunters becoming more concerned. Can you tell everyone sort of... You mentioned it started in a captive mule deer herd in Colorado, it’s in Wyoming. Can you give folks an idea of how the natural progression of the disease over the last few decades and where it's now located?

08:21 DE: Yeah, sure. So it started as you mentioned... It started in Northeastern Colorado and Southeastern Wyoming. And then it's kind of... Excuse me, sorry. It's popped up in new locations and it's been a slow but steady spread. It's found currently in 22 states, two Canadian provinces. We, through the game farm industry moved it over to South Korea. From the US to Canada and then to South Korea. And then it's just recently been found in Norway as well. So it's a slow but steady march outward. We... In some cases we know how it was spread such as through the game farm industry, and in other cases such as New Mexico or Texas we really don't know how it got there.

09:09 DD: Okay, so can you talk a little bit, because I don't know much about this, the game farm industry just as some background of how this disease could possibly get transmitted to other areas.

09:23 DE: Sure, so I don't mean to say that the game farm industry is the only way that it could be spread. But we do know it's easier to track farmed individuals than it is to track wild animals. And so that's why in some cases they've been able to track it through the game farm industry. And of course like any agriculture, farmed deer and elk are moved from farm to farm. And if a farm has CWD but does not realize it, then they could be transferring CWD-positive animals. And that was the case with how it got up into Canada for example, CWD-positive, I think it was Rocky Mountain elk, were moved to Canada and then that game farm became positive because of course, they're infectious.

10:06 DD: Okay, and can you explain the different modes of transmission of this particular disease and maybe touch on some of the more well-known for example, BSC or mad cow disease, we know can be spread via consumption of contaminated food products. So can you explain, you talked about scrapie some of the... Kuru explain maybe to everyone... There's several prion diseases but I know that they're transmitted a little differently.

10:42 DE: So that's right, yeah. So mad cow disease and kuru are similar in that they're not infectious in the normal sense, in that they have to... They're spread through the consumption of contaminated meat and neurological tissues. So in the case of kuru it was ritualistic cannibalism in the Fore tribe of Papua New Guinea. Who because they were consuming their deceased, were spreading this disease from generation to generation. Once it was determined that that's how it was being spread, they stopped this ritualistic cannibalism and the disease went away. Same with mad cow disease, it was not infectious from individual to individual other than in contaminated bone meal. And so once it was determined that if you remove that bone meal from feeding cattle, the epidemic was... Came to a halt. However, in scrapie and in chronic wasting disease, it's a different situation where individuals can spread the disease directly from individual to individual. As well as from individual to the environment and then from the environment to a susceptible host.

12:02 DD: Okay, so I have a... Here's the million dollar question and I think this is always confusing to me. How are proteins infectious? When we talk about... These aren't obviously bacteria, they're not viruses, they're not fungi, the classic infectious disease. So, can you speculate on or tell us what the latest research is on like how a protein is infectious?

12:32 DE: So you are getting a little out of my area of expertise for sure, but the common theory and it's still a theory, I don't think anybody fully understands our knows yet, but the theory is that it basically acts as a template. So when the infectious prions come in contact with the host cellular normal prions, they cause the protein to unfold and then to reconfigure itself into the infectious prion shape. And so it gets down to alpha and beta structures and proteins and stuff that I would rather not get into. But it's basically the idea is that it's a seed that acts as a template and that template causes the normal shape to change.

13:21 DD: Okay. So, I have an easier question, I know it's pretty complicated, what species are impacted by CWD first of all? And how did it jump from mule deer... I know it affects other species. But if you have any sense of how it got there from one species to the other.

13:46 DE: Yeah. So, the susceptible host in North America are white-tailed deer, mule deer, Rocky Mountain elk and moose and the susceptible species in Norway so far are reindeer and moose. So, let's just focus on North America. It was originally discovered as you mentioned in mule deer and through captive studies, it's been shown that it's easily transmitted between all four of the natural hosts... Sorry, all three of the natural host, moose are not very well-studied yet. So we'll kind of ignore moose for now because there's been so few cases and there's been so little research done on them, but mule deer and white-tailed deer and elk, it can basically be assumed that they're easily transmitted... That CWD can be easily transmitted between the three hosts with different susceptibility by species, but it's still possible for say a mule deer to infect an elk.

14:50 DD: Okay. Have there been any cases of CWD spreading to domestic animals like cattle or horses, or... I mean, I know some obviously the deer are farmed, which you could say would make them domestic, but any other, what we commonly think of as domestic species.

15:12 DE: So, thus far there have been no documented cases of prion disease being transmitted from deer or elk into what you traditionally consider domesticated animals. And there was just recently a study published in cattle that showed that cattle that were housed with CWD-positive animals did not acquire the disease after 10 years. There's varying susceptibility of individual animals through, say, intracranial inoculation where they actually inject brain matter from CWD-positive animals into individuals of a different species, and there's varying levels of susceptibility in that manner. But in a natural... Natural transmission has never occurred.

16:02 DD: Okay.

16:03 DE: To our knowledge.

16:04 DD: And I know this is sort of a hot potato, but as far as I know, there's been no documented cases where people felt it was transmitted to people, but I know there's concern about that.

16:19 DE: Yeah. So, there's always going to be concern because it's so hard to prove a negative. So, until it actually happens, there's always going to be a belief that is possible. In the popular press, there's been a study and I don't believe it's been published yet but the researchers have been presenting this research at various conferences where macaque monkeys were fed CWD-positive steaks from white-tailed deer, I think it's white tailed deer, and they became CW... They became positive for a prion disease. And so that's the closest relative that has acquired the disease through what would be a natural route, and that did produce a little bit of shock waves in that it seems like if that's possible, then what about humans? But as to date, no human has ever been documented to acquire a prion disease from CWD-positive animals.

17:17 DD: Okay. So, I have a question about testing. How do you test an animal, particularly like if you were a hunter for CWD, what tests are available and where would you locate them?

17:32 DE: Yeah. So, you would go to your local state diagnostic lab, or to your local game and fish office, and game and fish usually will collect samples for free, because they're looking for surveillance. If you take it to a veterinary diagnostic lab, you're probably going to spend a little bit of money. Last time I had an animal tested, I think it was like 25 bucks. So, it's not very much money and they just collect a lymph node from the neck, they might collect the brain stem and they test those using what's known as an ELISA, or an enzyme-linked immuno assay and then they're confirmed by looking at a section under a microscope with specific staining that will attach to the prions.

18:21 DD: Okay. So, one further question then we'll dive into your specific research a little bit. What are the clinical signs of this disease in animals?

18:36 DE: So, the most obvious in chronic wasting disease is emaciation, of course, but there's also loss of muscle coordination, a staggered gait. Their head and ears droop, their hair coat looks really rough and dull. They just look sickly, right? They'll drink excessively, like constantly drinking and dunking their snout up to their eyes trying to get as much as they can. Along with that excessive drinking, they have excessive drooling and excessive urination. In captive facilities, they lose their fear of humans, and they have kind of a decreased response to stimuli, so they... You could clap your hands and while they would usually run away, they're just going to stand there.

19:24 DD: Okay.

19:25 DE: Those are the general clinical signs.

19:27 DD: Yeah. It sounds a little bit like the signs you see with rabies almost, some of the compulsive water and neurologic signs. So it sounds like...

19:37 DE: That's a good comparison.

19:38 DD: So it sounds like just from clinical signs alone, it could look like other diseases.

19:45 DE: Yes. That's true. Clinical signs are not conclusive. You always have to test.

19:52 DD: Okay. So, to move to your research, the first question I had was why... I mean it sounds like a scary disease, why did you decide to do research into this particular disease when you were embarking on your graduate studies?

20:09 DE: Well, I kind of came across the project fortuitously, in that I was actually a technician working on the research project just trapping deer in the winter time and tracking them by radio telemetry, and this was between my Bachelor's and Master's degree, and I developed a rapport with Dr. Beth Williams who was one of the principal investigators on the study, and I inquired about making it my research for my Master's degree and she accepted me on to the project. So it was through a fortuitous route, but I've always been interested in diseases, I've always been interested in veterinary science, and then of course, I was a wildlife sciences undergrad, so it was a nice combination of all three of my interests.

20:56 DD: So... Oh, go ahead, Dave.

20:58 DE: Well, I was just going to say in CWD, there's just not... Especially at that time, there wasn't a whole lot known about it, so there were lots of good questions to ask.

21:05 DD: Cool. So, I know the Foundation wasn't your only source of funding, but can you talk a little bit about your Morris Animal Foundation study, kind of what you were... What your objectives were, and even go a little bit into the methods that you used to try to achieve those objectives.

21:26 DE: Sure. So, we were interested in looking at population-level effects of chronic wasting disease in a free-ranging white-tailed deer population in southeastern Wyoming, and we were also interested in looking at how chronic wasting disease affected the behavior of white-tailed deer. So we're looking at both the ecology and the epidemiology of CWD, and we did this using a field-based study where we captured deer as fawns in the winter time. We tested them for chronic wasting disease using what's known as the tonsil biopsy, so we took a small sample of the tonsil and then looked at it under microscopic slides for staining for CWD. And then we tracked a deer throughout their lifespan, recapturing them annually. As they became adults, we marked them with global positioning system collars, and we resampled them every year for CWD, so at least once a year, they were getting tested for chronic wasting disease, and weekly, we were out there on the ground, tracking them with radio telemetry. And through collecting a variety of data, we were able to look at the population growth rates, so how... By what percent the population is either growing or declining. We were looking at survival rates, pregnancy rates, what they died from, home range size, what size of habitat are they selecting for in their landscape, and what was in that habitat are they looking for, yeah, I think that's basically it.

23:07 DD: Okay. I know... Oh, go ahead, Dave.

23:10 DE: I would say too that it was a long-term study, so we are out there for eight years tracking these guys.

23:13 DD: Wow. I know the answer to this, but I was... I thought this was really interesting when I was reading your study, which is... Can you tell everyone why in particular the behavior... You wanted to look at the behavior of these individuals?

23:33 DE: So, we're interested in behavior to look at how possible routes of how the diseases spread. And so, if they for example, if they're becoming more sedentary, then the prions are likely getting concentrated in the environment, or say if they become more active and they start wandering around, then they're going to come into contact with more individuals, then it's more likely to spread faster, for example.

23:58 DD: Okay. So in other words, how abnormal behavior might influence versus what "Normal deer behavior" would be like to that impact it, and I have a question.

24:08 DE: Yes.

24:09 DD: What were your conclusions from your study that you found?

24:17 DE: So, the main conclusion we determined was that chronic wasting disease along with hunting does indeed cause this popular... Cause this population to decline. We've found that it was declining by a rate of 10.4% per year, which is the first documented population decline attributed to chronic wasting disease. And that was certainly our main finding. It's also one example of a chronic disease in wildlife that became endemic and caused through decreased survival, this population to decline which is interesting as well. We found that survival rates among CWD-positive deer were lower than those in CWD-negative deer, which is intuitive, but still interesting to determine. Because of this, we concluded that really the best management practice, because CWD has this potential to cause population declines, the best management is really to minimize the spread of CWD to new areas. Some other ancillary findings, we found that CWD-positive deer were more likely to be harvested, than CWD-negative deer, which a couple of other studies have found, but a couple of other studies have found the opposite of that.

25:37 DE: Kind of an interesting finding, we found that CWD prevalence was higher in our females than our males, and that's unique to this population, and something that we wonder if this might actually start to occur in other populations, because this is a population that's had CWD for a long time, and most populations just have recently acquired the disease. So we're wondering if that's something that might occur where the bucks become less commonly infected compared to the females.

26:05 DD: Okay, so I have a question. Did the results surprise you? Were there any surprises or were you... Was this kind of... When you made your hypothesis, is this a finding you expected or what were your feelings about what you found?

26:22 DE: I think the decreased survival rates in CWD-positive deer was to be expected and, deep down, I thought that this population was likely declining, because of decreased survival specifically in female deer, which is what we found. But I think the magnitude of the decline surprised me, and my other researchers as well, especially my graduate school advisor, Todd Cornish, Dr. Todd Cornish. He and I, I think, were surprised by the magnitude of the decline. 10.5% per year is a fairly major decline, especially in a white-tailed deer population. White tails have the highest reproductive rate of any cervid species in North America, cervid being deer. And so, if it's declining at that rate in white-tailed deer, say what's happening in mule deer was certainly a concern.

27:13 DD: Right. And I, again, I have the advantage of having read one of your papers that came out of this study and I think most people, listeners, everyone, feel like white-tailed deer are pests, right? A lot of people get frustrated because they eat your flowers and they dig up your bulbs.

27:33 DE: Sure.

27:35 DD: But I think that maybe you want to comment about the potential loss of this species that we think of as being plentiful.

27:47 DE: Yeah, so, it's certainly possible for white-tailed deer to become locally extinct. We've done it back in the... What was it? The 1950s or so, sorry not the 1950s, 1850s, back when there was high levels of harvest and white tails have been moved around the country in order to re-populate certain areas for hunting purposes and other reasons. But white-tailed deer are native to Wyoming and losing a native species, especially a major ungulate, that serves ecosystem function, would be a major loss to the habitat, and to the ecosystem.

28:31 DD: So I have a question. And we'll get into this later, your new research focus, but are people using your results or building on them, either at University of Wyoming, or elsewhere?

28:46 DE: Yeah, so Dr. Melia DeVivo, she got her PhD on a very similar project. So Todd Cornish brought her on as a PhD student and she did a very similar project to what I did in white-tailed deer, in mule deer. So that was certainly building upon the concept of our study. As far as the results, I spoke with the wildlife veterinarian for Wyoming Game and Fish here recently, and she said, in part, because of my findings or our findings I should say, and the findings from Dr. Melia DeVivo's study, Game and Fish is rewriting their wildlife, or their CWD management plan, trying to become more proactive, and hopefully lower the prevalence, or prevent it from increasing, prevent CWD from spreading into new areas. So that was really positive to hear that, because of some of the work that we did, Game and Fish is becoming more proactive. That's great to hear.

29:49 DD: Okay, so that was one of the questions I had for you. What are people trying to do, worldwide, really, because it's becoming a global problem, to manage this disease, because it's spreading, as you mentioned?

30:06 DE: Yeah, so there's been a variety of efforts done. I think probably the most common effort is just surveillance for the disease, testing as many hunter-killed or hit by vehicle carcasses as game and fish agencies can get their hands on, in order to detect it as early as possible. That's certainly one management practice and then, many areas, when it is detected, they then go in and locally cull as many deer as they can in the area. The idea being, so New York State did that, I think it was 13 years ago, and they had a couple of cases. They went in to the area, and they killed as many deer as they could in the surrounding area, with the idea of testing all of those animals to see just how common it is. But also, if you remove that one positive deer, assuming it is the one positive, then maybe you can remove CWD before it becomes endemic to an area. And in the case of New York, they never had another positive. They have not had another positive yet. Norway, as soon as they detected CWD, they went in and eradicated their entire caribou herd, or reindeer herd, I should say.

31:19 DD: Wow.

31:20 DE: So, pretty drastic measures in those cases. A lot of states, Colorado being one, Wisconsin and Illinois being a couple of others, have tried just reducing the density of the herd. The idea being that if you reduced the density, then you've reduced the number of deer that CWD-positive animals come in contact with and, hopefully, then reduce prevalence. It has never been shown to actually reduce prevalence, but in the case of Illinois, they were able to at least keep the prevalence steady or stable.

31:55 DE: What other regulations? There's regulations with what parts of the carcass, within CWD-endemic areas, you can take out of that region. So, hunters are encouraged to leave the majority of their carcass either at the kill site or take it to a dump, and just take the meat home to their home state. There's of course, game farm industry is regulated, where the game farmers need to test a certain number of their mortalities each year, in order to try and to detect CWD, and then if they do acquire the disease in their herd, again, herd eradication, and then leave the farm. I think it's followed for five years before they're allowed to re-populate. So, those are the main... Oh, and then, I guess the last one is, there's recommendations on how to process hunter-harvested animals to try and prevent exposure of the hunters to prions, just in case there is the potential for CWD to spread into humans.

33:08 DD: Okay. So what do precautions do people have to take? What do people recommend? And what did you take, for example, being out in the field when you're looking at these individuals?

33:20 DE: So the main precautions are to wear gloves when you're handling an animal, be it capturing them or processing them. We had to, because we were performing a minor surgery on the animals, we had to disinfect our instruments between each individual that we processed. It's always a good idea to disinfect your hunting knife and whatever, you're cutting boards, etcetera, if you butcher. And then the other precaution is to try and avoid cutting into the spinal cord in hunter-harvested animals, to try and minimize exposure to the neurological tissue.

33:56 DD: Okay. So I have a question because this happens, and I live in Colorado too, is, if you come across, for example, a road kill, I'm assuming, don't touch it.

34:08 DE: Yeah, that's right, don't touch a dead animal, if you can avoid it.

34:12 DD: Okay, so I have a question, I think we get it a little bit, but what concerns you most about this particular disease?

34:24 DE: I would say the main concern I have is that we really just don't have great management tools at this point, once the disease becomes established. So, especially with our study, now that we know, and Melia's study, that we know that CWD can cause population declines. Well, that's a major concern, particularly for species that are like mule deer and elk, that people care more about than white tails, as you mentioned. Once it's established, we really have no way of controlling the disease and that's my main concern.

35:00 DD: And why, I guess, this is a kind of loaded question, but why should people, in general, care about this particular disease and these declines on populations that we typically... You indicated you can have local extinctions, but I think, if you could make a plea to people about why they should be concerned, what would you tell somebody?

35:27 DE: Well, I think everybody enjoys seeing deer on the landscape or elk on the landscape and so, if you're a hunter, or you're a non-consumptive user who just enjoys seeing animals out there, well, this disease has the potential to either cause local extinction, so you're not going to see any animals in an area, or at least population declines, where you're going to see fewer and fewer animals. And so, if you care about seeing animals, then you should care about this disease. Also, it's just, it's not a nice disease. It's not a nice way to die. And if you care about the welfare of an animal, then you should care about this disease not spreading into new areas.

36:12 DD: Right. I think we are just about done, but I was going to ask you, just very briefly, but we don't have to go into it, if you want to just tell everyone what your research focus is now, what you're working on in your lab.

36:29 DE: Okay. So my current research is, I've gotten away from disease research, and I've gotten back into my wildlife sciences background, where I'm currently in a lab that focuses on sagebrush and sage-grouse in particular. I don't do a whole lot with sagebrush, but I do do a lot with population dynamics. So are populations increasing or decreasing in sage-grouse populations, primarily in Wyoming. Sage-grouse, of course, are a major political and hot button topic and a species of concern. So that's the impetus behind working with sage-grouse.

37:08 DD: Right. So I want to end and I want to thank you for doing the interview today, with a question that rages around our office and maybe you can settle this one, for once and for all, is it prion or prion [chuckle]?

37:24 DE: I've always called it prion. I've heard prion. Prion seems to be more from people who come from say, the United Kingdom. But I would go with prion.

37:37 DD: Okay. So it's either like tomato, tomato sort of thing. So it's a UK thing? [chuckle]

37:45 DE: Yeah.

37:46 DD: Well, that's really great. Well, thanks a bunch, Dave, for coming on and talking about your research and we are very proud, at the Foundation with what you accomplished. I know it was a long study, but I think it was super important, and I know you have some great publications out there that, for our listeners, we actually have links on our website. We wrote a blog about this last year as well. And so, again, thanks to Dr. Dave Edmunds for joining us today on the podcast.

38:20 DE: Oh, you're very welcome, and thank you for having me.

38:22 DD: You're welcome. So I'd like to wrap up by saying, another thank you to Dr. Dave Edmunds for joining us today, and for everyone out there who're listening in. And I hope you'll join us again in the future as we produce and post more of these podcasts. If you have any questions, or you want to learn more about the Foundation, please go to our website at, and thanks again.