Interview: Dr. Peter Daszak, executive director of the Consortium for Conservation Medicine, discusses animal health

06/08/2002
NPR: Weekend Edition - Saturday
Copyright 2002 National Public Radio, Inc. All Rights Reserved.

ALEX CHADWICK, host: This is WEEKEND EDITION from NPR News. I'm Alex Chadwick.

Coming up, music from the heart of Africa, but first scientists all over the world are tracking the health of wildlife populations and the news is not good. Gorillas in Rwanda are contracting human diseases not found before in the wild. Amphibians such as frogs are developing mutations. Entire species of frogs are vanishing, some from suspected diseases. What causes these problems for wildlife, and what might this unsettling news portend for humans? These are among the questions being asked this weekend at a scientific conference here in Washington, DC. The conference is called Healthy Ecosystems, Healthy People.

One researcher presenting a paper at the conference is Dr. Peter Daszak. He's executive director of the Consortium for Conservation Medicine in Palisades, New York. And he joins us in the studio.

Thanks for being here.

Dr. PETER DASZAK (Executive Director, Consortium for Conservation Medicine): Hi. Good to be here.

CHADWICK: There've been a lot of efforts in recent years to protect wildlife, animal wildlife, reserves and that kind of thing. What's causing so many animals to develop these new kinds of diseases?

Dr. DASZAK: Well, that's really what the Consortium of Conservation Medicine is all about. We're trying to find out the underlying causes that drive these emerging infectious diseases in wildlife. A couple of years ago we analyzed the diseases that we knew about in wildlife populations and started to see similarities between the diseases we call emerging diseases in humans and those that are in wildlife. And sure enough, wildlife suffer from a whole series of emerging infectious diseases that are causing loss of populations and also even, in some cases, species extinctions.

CHADWICK: We mentioned gorillas in Rwanda. What kind of human diseases are affecting gorillas there?

Dr. DASZAK: Well, there have been reports of two groups of non-human primates, so gorillas in Rwanda, chimps at the Gombe Park, where ecotourism has been a way of combating the conservation problems there.

CHADWICK: That's Jane Goodall's study site.

Dr. DASZAK: Yes, exactly. And Jane Goodall actually suggested that chimps at Gombe were suffering from polio, a human disease that they shouldn't really have out there in the wild. There's been a lot of physical contact between those gorillas and humans. And that's a really good way for a pathogen to move from one to another.

CHADWICK: Can I ask you just to define the word pathogen for our listeners who might...

Dr. DASZAK: A pathogen is a virus or a bacterium or a microbe, in general. A pathogen is some--is the agent of a disease.

CHADWICK: And these are what's emerging?

Dr. DASZAK: Yes. Exactly.

CHADWICK: We've heard of news over the last decade of these strange mutations that appear in frogs; frogs are an amphibian population. You study frogs.

Dr. DASZAK: Yeah.

CHADWICK: Are you able to say at this point `OK, we've learned enough in 10 years that we can begin to draw conclusions'?

Dr. DASZAK: Still not with the frog deformities. And there are really two issues affecting frogs right now that people are working on that are really significant, one of these deformities that we've seen throughout North America, and a couple of hypotheses are out there. One is that it's pollution or some other environmental stressor caused by humans. And another is that it's a parasite that infects the nodes as the limb grows and causes deformities. Even if it is the parasite, and there's good evidence that it is now, and it's a very interesting piece of work, what's causing that parasite to be increasing in prevalence or increasing in incidence and these deformities to expand? We don't really know yet.

CHADWICK: When you speak of frog species disappearing, which species are disappearing and how do you know what is driving them out of existence?

Dr. DASZAK: Yeah, it's very difficult. And one of the problems with extinction is that it's very difficult to be there when the last group of animals disappears and to find out what caused it. And, for instance, the golden toad, which is a really beautiful animal and sadly disappeared and is now extinct from Costa Rica, there's been a lot of discussion over what caused the disappearance of that species. But we were present for one extinction and we did know what caused it and it was a disease, and this species is a snail species that was originally found in the South Pacific, Partula turgida. And it died out in London Zoo. Sadly the last group were in captivity and the disease--we don't know where it came from; we know what the disease is, microsporidiosis--moved into these snails and wiped them out. And work I conducted with Andrew Cunningham at the Institute of Zoology over there showed that the last--the very last group that died out, and the last individual of that species, was killed by this infectious agent.

CHADWICK: Why the focus of the conference this weekend, looking at the changes in diseases in animal populations, and saying, `Well, there's something there for humans as well,' or how do you apply one to the other?

Dr. DASZAK: You know, there's a whole slew of people out there now who are beginning to use the word `sentinels'--you know, the canary-in-the-mine sort of approach. And what these scientists are saying is that wildlife populations are in fact sentinels for our own health as a population. If wildlife is suffering from these outbreaks of very unusual diseases in new places, then surely the same is happening to us. If the causes are similar, and it turns out they more or less are, then we can use wildlife as sentinels for our own health.

CHADWICK: HIV, famously, is a disease that moved from animal populations to human populations. Are there others out there that threaten us?

Dr. DASZAK: Well, actually, the consortium's just set up a team of people to work on nepovirus and Hendra virus. These are probably less well-known, certainly less well-known than HIV or West Nile virus. But they're very significant and they represent a group of measleslike viruses that emerged from fruit bats into humans in Australia and Malaysia. And if one of these happens to be very efficient at spreading from one human to another, then we've got a potential for a serious global outbreak.

CHADWICK: You say there are emerging diseases now. We recognize emerging, newly emerging diseases. Isn't there, for some reason, a greater gross number of diseases today than there were a hundred years ago, a thousand years ago, a million years ago?

Dr. DASZAK: When you look back, historically, you can probably imagine periods in time when animals moved from one area to another and carried disease or humans moved from one area to another and carried disease. But really what happened was we started to come together into larger and larger populations with the capacity to support diseases that rapidly kill people, things like measles virus. You need a certain number of people in one area to support the virus like measles. So once humans started to come together in these populations, we allow diseases to emerge into the population so increase the number of diseases out there, and certainly the impact of those diseases.

CHADWICK: There's renewed interested again this week in global warming. Is that a factor in the spread of these pathogens and newly emerging diseases?

Dr. DASZAK: Indeed, it is, and it's possible that when you've got a pathogen and climate change, these can act together; one can drive the other, and cause extinction that way. One of the key things, if you're thinking about climate change, is that we can't be isolationists in this globalized planet. If we try and keep ourselves separate to developing countries and say, `We're going to be OK during climate change,' what's going to happen when diseases that emerge out in other countries, developed countries, that aren't doing so well in a changed world, spread back into our populations? These big environmental changes are going to spread disease.

CHADWICK: Thank you, Peter.

Dr. DASZAK: My pleasure.

CHADWICK: Dr. Peter Daszak is executive director of the Consortium for Conservation Medicine in Palisades, New York. And he's speaking this weekend at a conference in Washington, DC, Healthy Ecosystems, Healthy People.