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Program ID: Innovation Anthology #874
Program Date: 06/06/2017
Program Category: Alberta, Health and Medicine, Wildlife, Women in Science

Dr Evelyn Merrill: Chronic Wasting Disease

PROGRAM #874   INTERVIEW WITH DR EVELYN MERRILL

MP3:    34 MB

TIME:  14:52 MINUTES

Intro:  Dr Evelyn Merrill is a Professor in the Department of Biological Sciences in the Faculty of Science at the University of Alberta.  She studies large mammals like deer, elk and moose and is an expert in Chronic Wasting Disease.  With funding in part from Alberta Innovates, she is engaged in two field studies that seek to establish how CWD is most likely transmitted between deer and how the spread might be predicted. 

DR EVELYN MERRILL 

CC:  EVELYN, YOU'VE BEEN LOOKING AT CHRONIC WASTING DISEASE IN DEER FOR A NUMBER OF YEARS.  WHAT GOT YOU INTERESTED IN THIS? 

EM:  Well, Chronic Wasting Disease is a disease of cervids and it’s a fatal disease.  It's one that I believe is going to have a significant impact on the populations of deer in particular in Alberta.  And this is a species that I've been working on, along with elk and moose to some degree for the last 35 to 40 years of my career. 

So it really is a disease of a particular group that I've been working on and studying for many, many years. 

CC:  AND WHEN DID IT FIRST APPEAR IN ALBERTA? 

EM:  Let's see, it was in the late fall of 2005 and it was then found again in 2006 on the eastern portion of the province. 

CC:  AND HOW FAR HAS IT SPREAD OVER THE YEARS? 

EM:  It kind of plods along.  It's a slow, progressing disease.  And it has progressed westward toward Edmonton.  But it hasn't quite yet reached that area.  There was one long range kind of what we call a jump in the disease.  That was out by Miquelon Lake area but otherwise it's mostly in the eastern portions of the province. 

CC:  AND WHAT DOES IT ACTUALLY DO TO THE DEER AND ELK? 

EM:  It's what's called a TSE or a Transmissible Spongiform Encephalopathy.  And basically what that means is that it’s a nervous system disorder. 

What you will see in the clinical signs is that a deer will essentially lose weight, its head will droop down, its ears and eyes will be very, like you know it’s sick.  It will salivate quite a bit.  And eventually 100 percent, if they get it, they will die. 

CC:  AND HOW TRANSMISSIBLE IS IT? 

EM:  Well it's transmitted both animal to animal and through the environment.  So there are many roots through which one animal can infect another. 

But we really don't know at this point what the major route is.  We suspect it's animal to animal, and that could be in saliva; it could be urinating and then smelling it.  We really don't know what the main driver is.

We know that it can be transmitted through several different body fluids and even through soils where body fluids are excreted into. 

CC:  AND DOES IT REMAIN IN THE ENVIRONMENT FOR A LONG TIME? 

EM:  Yes it does.  There are estimates of ten to twenty years.  What we don't know is how accessible it is.

In other words, it might be deposited on the surface but how well then it sinks into the ground in a particular place, so the animals are not exposed to it.  We don't know that… 

We do know from experiments that it actually can be taken up in the roots and now the stems of different plants.  So that's another possible mechanism for it as well. 

CC:  AND I KNOW FROM TALKING TO OTHER RESEARCHERS WHO ARE LOOKING AT OTHER FORMS OF PRION DISEASES, THESE THINGS ARE PRETTY WELL INDESTRUCTIBLE. 

EM:  Yes.  They're not like bacteria that you can heat to a certain temperature and they'll die.  It's not a virus.  It's not a bacterium.  It's a prion, as you probably know, and that basically acts like an infectious disease but it's really a protein that misfolds.  And then by contact, misfolds another protein and acts as an infectious agent. 

CC:  NOW YOU HAVE A FEW PROJECTS ON THE GO.  ONE THING I UNDERSTAND YOU'RE DOING IS TRYING TO FIGURE OUT HOW IT IS THAT THE DISEASE IS MOVING OUT ACROSS THE PROVINCE, AND WHETHER OR NOT YOU CAN DO ANY PREDICTION ON THAT.  PERHAPS YOU COULD EXPLAIN THAT TO ME PLEASE.

 EM:  Sure.  I'm involved with two major studies. 

The first one is a field study where we're trying to understand how it is transmitted among individuals and in the environment.  And so for this study, we have actually put on some radio collars that record when two animals come within close proximity to each other. 

With those collars then we are trying to look at the seasonal rates of contacts, how the environment such as dispersion of the trees or different habitat, such as open agricultural fields, might affect the contact rates both within the different sexes, the males to males as well as males to females.  And really to quantify that seasonally so we can make some predictions in which environments we might see it transmitted faster. 

CC:  HOW ARE YOU GOING ABOUT THIS? 

EM:  Well we capture and collar the mule deer.  The focus is on mule deer.  And these animals then, we monitor them through satellites and we can watch their movements.  And then the collars also record when two animals get together.  So we know the type of place where they get together.  We know how frequent that is.  And then over time we can actually model that as a function of different factors, such as the configuration of the habitat or the amount of river drainage which deer tend to like in winter, as well as the population level of the deer in the area. 

CC:  SO YOU MUST BE COLLECTING QUITE A DATABASE OF INFORMATION? 

EM:  We have been and we've tried to do this in small areas where we can control the exact types of configurations of the habitats, the number of animals, and have a good estimate of the densities as well.

CC:  OVER WHAT PERIOD OF TIME DO YOU FEEL THAT YOU WOULD HAVE TO DO THIS TO FEEL CONFIDENT IN THE MODEL THAT YOU ARE DEVELOPING? 

EM:  Well the small scale studies are probably going to go on for about three to four years.  That's our plan right now.  We think in that amount of time that we will be able to come up with some general patterns and factors that are affecting them. 

With our models then, we hope to take those and actually then predict from areas where we know it exists, where it might spread to and areas in which it will increase in the population itself. 

We have a relatively low percentage or what we call prevalence in the province right now--about three percent on average or just under that for mule deer.  But we expect that to increase over time.  And our modelling hopefully will help target what areas that's going to happen in. 

And if we know that, then we can direct our surveillance of it as well as any management tools that we come up with to manage and control the disease. 

CC:  SO YOU'VE MENTIONED MANAGEMENT.  WHAT DO YOU FORESEE AS BEING SOME TYPES OF MANAGEMENT THAT COULD BE USED? 

EM:  Right now we always hope that we can come up with a vaccine.  But despite some early hope on the developing a vaccine, it doesn't seem to be in the immediate future. 

And even for free ranging populations, vaccines are very difficult and actually quite costly to dispense, because you have to get the animals to actually eat it or you would have to inject them.  And that's pretty invasive. 

So vaccines don't seem to be a tool that's going to be in our toolbox in the next few years. 

Keeping populations lower, mostly through harvest management, letting hunters do the job, I think is what the Alberta Fish and Wildlife is really looking to in the future. 

IS THERE ANY CHANCE OF THIS TRANSMITTING FROM THE ANIMALS TO HUMANS? 

EM:  There's no known evidence for it for transmission to humans at this time. 

However, despite that, people are very cautious in what they talk about.  There is some new work going on with macaques that I think they are finding there may be some evidence that it can be transmitted orally to macaques, but that work is only in its very early stages. 

So right now there really is no substantive evidence that it would be transmitted to humans. 

CC:  DO YOU THINK THE SPREAD OF THE DISEASE IS RELATED IN ANY WAY TO CHANGES ON THE LANDSCAPE THAT WE EXPECT DUE TO CLIMATE CHANGE IN ALBERTA? 

EM:  I think that the deer population, at least in the long term, could be affected by some of the changes we might see in habitat changes.  Those will be pretty slow in the next few years.  So I don't think that's a big factor at this point in time.  

Climate change is probably not the most important one. 

Now, other land use changes, where we change the distribution of deer and cluster them on the landscape, so they have these higher contact rates once the disease is established in an area, that certainly could increase the rate or slow down the rate, depending on what that change is.  

CC:  WHAT ARE SOME OF THE THINGS THAT YOU'VE FOUND OUT SO FAR? 

EM:  Well we're just at the beginning of our small scale studies, so it’s really too preliminary to say anything.  Some of our past modelling though has told us that the deer movements are along these river drainages and so is some of the winter habitat. 

And if you look at the spread patterns of CWD in animals that are harvested on the landscape, you can see that it doesn't equally spread out across the landscape.  It really does follow the areas where the best habitat is for the deer and where they are moving. 

CC:  NOW I UNDERSTAND THAT ALBERTA INNOVATES HAS HELPED OUT WITH SOME OF THE FUNDING.  WHAT WOULD THEIR ROLE BE? 

EM:  Well they do a very good job of peer review and they fund some of the best work here in Alberta and elsewhere on Chronic Wasting Disease and other prion diseases. 

They are funding me in two ways.  First for these small scale studies but also I'm part of a larger collaboration that they are providing matching funds with for a project with Genome Canada.  And in that work we are actually looking at incorporating how vulnerable certain genome types of mule deer, whitetail deer, and other cervids are into our modelling processes. 

So one area, we have certain, a higher frequency of genotypes in that area, and they're the ones that are the most susceptible to the disease, then we expect to actually see it spread faster and increase in the population faster. 

And we're starting to map those genotypes across Alberta and parts of Saskatchewan over the next four years. 

CC:  COULD YOU EXPLAIN THAT A LITTLE BIT MORE TO ME.  WHAT DO YOU MEAN BY GENOTYPES AND HOW MIGHT THEY DIFFERENTIATE BETWEEN THE DEER? 

EM:  So when we get harvested animals by hunters back, we take a small piece of muscle and from that, we are actually able to determine the genetics of that deer. 

And there are certain alleles that we have found are associated with either resistance to the disease or vulnerability to the disease. 

Now, resistance might be something along the lines that, you can get the disease but you don't die as quickly from the disease if you're of a particular genetic makeup. 

Now that might seem good at first glance but what could happen, even though they're not dying as soon, they actually are spreading it much more widely during their lifetime; whereas if they had died more quickly, they would not be infecting as many animals or even transmitting it to the environment. 

So how the genotypes, which is the genetics of the animal, interact with the disease, is going to really influence how we see it change over time in different populations. 

CC:  AND YOU MENTIONED THIS IS PART OF A LARGER COLLABORATION.  WHAT ARE SOME OF THE OTHER DISCIPLINES THAT ARE INVOLVED IN THIS? 

EM:  Well, we have all the way from social scientists to people who work in proteomics.  It’s a very large collaboration focused on CWD to try to really get a handle on how it works, how can we detect it better in the field.  And once we detect it, understand how we might prevent it from spreading by developing management tools. 

Chronic Wasting Disease is a really tough one to deal with.  It's hard to detect in the environment.  We don't know the major routes of transmission at this point.  Our live tests are now only beginning to come on target so we can use them. 

We really have struggled quite a bit with this disease.  And meanwhile, it is spreading across North America.  And it has caught a lot of attention from wildlife agencies in both the United States and Canada.  Because again, it now has shown it can have some population effects. 

So I think this is something that we really do want to put some effort to.  As you've seen at the Alberta Prion Research Institute and Bio Innovates really do this. 

And I think it’s well worthwhile because this is a very insidious disease. 

CC:  THANK YOU VERY MUCH, EVELYN. 

EM:  You're welcome.  And thank you for taking the time to talk to me.  

Dr. Evelyn Merrill is a Professor in the Department of Biological Sciences at the University of Alberta.

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