Prime Time Replay:
Andy Dobson
on the link between biodiversity and human health
MsgId: *breakthrough(1)
Date: Wed Nov 19 20:53:26 PST 1997
From: moderator At: 152.163.201.7
Welcome to Breakthrough Medicine. I'm your host, Madeleine Lebwohl, and tonight I'll be speaking with Andy Dobson, who is a professor of epidemiology and conservation biology in the Department of Ecology and Evolutionary Biology at Princeton. Tonight we'll be conducting an in-studio interview. Hi, Andy, welcome to Breakthrough Medicine.
MsgId: *breakthrough(3)
Date: Wed Nov 19 20:57:54 PST 1997
From: moderator At: 152.163.201.7
AD: Hi.
MsgId: *breakthrough(4)
Date: Wed Nov 19 20:58:50 PST 1997
From: moderator At: 152.163.201.7
Could we begin by discussing you work, which links biodiversity and human health.
MsgId: *breakthrough(5)
Date: Wed Nov 19 21:00:52 PST 1997
From: moderator At: 152.163.201.7
AD: Predominantly I'm interested in animal health, and obviously that is an important component of human health, if we eat animals. The majority of infectious diseases we have usually have come to us through the species we've domesticated.
MsgId: *breakthrough(6)
Date: Wed Nov 19 21:01:42 PST 1997
From: moderator At: 152.163.201.7
How is biodiversity involved in this process?
MsgId: *breakthrough(7)
Date: Wed Nov 19 21:03:40 PST 1997
From: moderator At: 152.163.201.7
AD: Well, for example, two of the problems that I work on: Bison, and brucellosis, in Yellowstone park, and rinderpest virus, in Serengetti, in Tanzania. In both those cases you have diseases that can infect wild animals and domestic cattle, and in one case the disease is present in wild animals and we're worried that it might get into domestic animals, which is the Yellowstone case. In the rindapest case, we have a disease of cattle that can infect many of the species in Serengetti national park, and indeed the whole structure of the Serengetti ecosystem is a result of virus epidemics earlier this century.In both places people come in in two different ways. One, the local people, dependent on cattle, and two, tourists come to see the wildlife, and biodiversity, which brings money into the local economy, which in turn supports other groups of people. Now, in the case of rindapest in the Serengeti, since the late 1950's we've had a very effective vaccine, essentially because rindapest is essentially the ancestor of measles in humans.
There used to be epidemics, and indeed, numbers of many wild species, such as wildebeest and buffalo, were held at low densities by the pathogens. Curiously, once people started vaccinating the cattle the disease dissapeared from wildlife, indicating that the cattle were the reservoir, not wildlife. And you then got a massive increase in the numbers of wildebeest, buffalo. Wildebeest went from about a quarter of a million to a million and a half. This also led to an increase in predators such as lions and hyenas. It may also have led to a decrease in some woodland or some tree species, so woodlands became converted to grasslands, so essentially removing just one species and less than a beer glass of that virus has a dramatic effect on that ecosystem. And everybody benefits, there's more cattle for the people who look after cattle, and there's more wildlife for the tourists.
But our ability to maintain that is dependent on being able to mount an effective vaccination campaign, and of course, as with human vaccinations, the longer you vaccinate, the more people begin to look for ways to cut down on either themselves being vaccinated, or their domestic animals being vaccinated. Maintaining and understanding how to maintain an efficient vaccination campaign in that area allows you to maintain high levels of biodiversity and health number of cattle per human, and also increases the attractiveness of a tourist area for people to come in and spend foreign currency.
MsgId: *breakthrough(13)
Date: Wed Nov 19 21:16:04 PST 1997
From: moderator At: 152.163.201.7
Did people keep up vaccinations?
MsgId: *breakthrough(14)
Date: Wed Nov 19 21:19:04 PST 1997
From: moderator At: 152.163.201.7
AD: Occasionally the government or the international aid agency isn't able to keep their level of funding for vaccinations, and then you get an outbreak. An outbreak which imperils not only the local cattle population, but the human population which is dependent on the cattle. And you also run the risk that that infection will spread to wildlife, which could cause a massive reduction in biodiversity, which would in turn effect the tourist industry.
MsgId: *breakthrough(15)
Date: Wed Nov 19 21:20:41 PST 1997
From: moderator At: 152.163.201.7
Is there a connection between rindapest and measles now?
MsgId: *breakthrough(16)
Date: Wed Nov 19 21:22:18 PST 1997
From: moderator At: 152.163.201.7
AD: There are two connections. One, rindapest is the ancestor of measles in humans, either directly, or indirectly, having become distemper before becoming measles. We know the distemper- rindapest split was about four thousand years ago, and human measles appears about two thousand years ago.The other connection is of course the very powerful mathematical models that have been developed to look at measles in the human population. You can also use them to predict the vaccination coverage you need to prevent a rindapest or other disease outbreaks in the Serengeti, or Yellowstone, or other wildlife populations.
MsgId: *breakthrough(18)
Date: Wed Nov 19 21:26:04 PST 1997
From: moderator At: 152.163.201.7
How does biodiversity help maintain health?
MsgId: *breakthrough(19)
Date: Wed Nov 19 21:28:24 PST 1997
From: moderator At: 152.163.201.7
AD: In an enormous number of ways. For example, all of the conversion of CO2 into oxygen is done by natural plant populations. Massive amounts of removal of pollution from water and air is done by free living plants and animals. Most of us are dependent in some way or another on biodiversity as a source of food. Even if we only ate fruit, that fruit has to be pollinated by insects, who provide that service for free.A group of people have recently calculated the annual economic value of services provided by biodiversity to the world's economy, and those figures suggest that biodiversity is worth twice the world's annual gross domestic product. So its maybe the major input into the world's economy.
MsgId: *breakthrough(21)
Date: Wed Nov 19 21:30:52 PST 1997
From: moderator At: 152.163.201.7
How did they define biodiversity?
MsgId: *breakthrough(22)
Date: Wed Nov 19 21:32:22 PST 1997
From: moderator At: 152.163.201.7
AD: The totally extant natural ecosystems in the world. That would include rivers, estuaries, deserts, forests, savannahs, the oceans, mountain regions, lakes.
MsgId: *breakthrough(23)
Date: Wed Nov 19 21:33:53 PST 1997
From: moderator At: 152.163.201.7
When people worry about loss or change in large ecosystems, like the rainforest in the Amazon, what is the damage to fear locally and globally?
MsgId: *breakthrough(24)
Date: Wed Nov 19 21:37:39 PST 1997
From: moderator At: 152.163.201.7
AD: Particularly climate, such as local rainfall. Cutting down the forest and burning it puts carbon into the atmosphere, which is leading to an increase in global temperature. This can lead to big changes in local climate conditions throughout the world, perhaps as soon as within the next twenty years. With more extremes of hot and cold, the variability of the weather will also increase. So more people will die of heat stroke in the summer, and more people will freeze in the winter. Which in turn will lead to people needing more air conditioning in the summer and more heating in the winter, which makes the situation even worse.We may also see a change in distribution in the geographical distribution of infectious diseases, particularly those which at present are confined to the tropics, such as malaria, cholera, sleeping sickness. And unfortunately this comes at a time when the drugs we had to control these diseases have almost entirely lost their efficacy due to the evolution of drug resistance. Also the other thing you lose when you chop down the rainforest is the potential for new drugs, which might replace the ones for which there is now resistance.
The resurgence of old pathogens due to both climate change and drug resistance is a much bigger worry than the emergence of new pathogens, such as ebola. Though the classic exception to that is HIV, which is a big worry. We have to remember that malaria was present throughout much of the United States as recently as 100 years ago, and in five years time we will have no drugs to treat it with.
MsgId: *breakthrough(28)
Date: Wed Nov 19 21:45:08 PST 1997
From: moderator At: 152.163.201.7
Is the work to maintain biodiversity being done now in an effective way?
MsgId: *breakthrough(29)
Date: Wed Nov 19 21:48:48 PST 1997
From: moderator At: 152.163.201.7
AD: Certainly, much of the scientific work that's being done to understand the evolution and maintenance of biodiversity is deeper and harder than the science involved with the structure of the universe or the making of the atom bomb, and certainly more ethically sound and crucial to the future of democracy. However, there are very few people working in these areas, and they're operating against, in many cases, areas of human enterprise that don't have a long term agenda.The Smithsonian Tropical Research Institute in Panama, has found out absolutely amazing things about how rainforests work, and the Institute of Economic Botany, at the New York Botanical Garden, continues to find tropical plants that are likely to be sources of new drugs that we're going to need to control infectious diseases both of humans and domestic livestock in the very near future.
MsgId: *breakthrough(32)
Date: Wed Nov 19 21:53:51 PST 1997
From: moderator At: 152.163.201.7
If we could go back a little, to your work at Yellowstone, are the bison in danger?
MsgId: *breakthrough(33)
Date: Wed Nov 19 21:58:01 PST 1997
From: moderator At: 152.163.201.7
AD: They're at much less healthy state this year than a year ago. There were four thousand a year ago, and there's just around two thousand now. This is largely a result of a mismanaged culling attempt by the local veterinary health authority, which killed about a thousand bison last winter, and then an unusually hard winter which killed about another thousand. Now the disease problem here contrasts quite sharply with the case in the Serengeti, in that brucellosis, is present both in bison and elk. Ironically, it was probably introduced into the bison from dairy cattle at the beginning of this century when the 12 bison present in Yellowstone park were one of the last few refuge populations of the millions of bison that once covered the whole of the Midwest.Unfortunately, the cattle industry perceived bison and brucellosis as a threat and has decided to try and eradicate brucellosis from the Yellowstone bison herd. If nothing else this illustrates the general malaise of epidemial understanding in veterinary training in the U.S., in that brucellosis is predominantly transmitted either from a female cow to her calf during lactation, or as an STD-a sexually transmitted disease. Therefore it seems unlikely that it will spread from bison to cattle. Unfortunately, the strength of the cattle lobby is such that it demands a reduction of the Yellowstone bison herd, which has a very direct impact on this particular component of biodiversity.
Personally I find this appalling, as saving the bison in Yellowstone was one of the first successes of national and international conservation. And indeed Yellowstone represents one of the few places in the United States where we still have a completely intact flora and fauna. This not only acts a sort of major tourist attraction, bringing many millions of tourist dollars into the area, but its increasingly a major attractant for emigration of human population into that area. It seems a major shortcoming that the declining cattle industry and the out-of-date veterinary authorities should have such a large a say in the future of biodiversity in that region.
MsgId: *breakthrough(36)
Date: Wed Nov 19 22:07:06 PST 1997
From: moderator At: 152.163.201.7
What other projects are you working on?
MsgId: *breakthrough(37)
Date: Wed Nov 19 22:09:16 PST 1997
From: moderator At: 152.163.201.7
AD: At the moment I'm finishing up writing a book on some long term work we've been doing in Scotland on how parasitic worms effect game bird populations. This is joint work with Peter Hudson, and that book should be out next year. And then I'm also writing a more general book on the ecology and evolution of parasites and infectious diseases. And that's with Les Real, of the University of Indiana.
MsgId: *breakthrough(38)
Date: Wed Nov 19 22:10:15 PST 1997
From: moderator At: 152.163.201.7
Thank you for joining me tonight on Breakthrough Medicine. Its been great talking with you.
MsgId: *breakthrough(39)
Date: Wed Nov 19 22:11:03 PST 1997
From: moderator At: 152.163.201.7
AD: Its been my pleasure, and I hope we can talk some time in the future.
MsgId: *breakthrough(40)
Date: Wed Nov 19 22:12:27 PST 1997
From: moderator At: 152.163.201.7
Goodnight, and please join me next week for Breakthrough Medicine.
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