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21 January 2000
Morning Edition
English
Copyright 2000 National Public Radio, Inc. All Rights Reserved.
BOB EDWARDS, host: This is NPR's MORNING EDITION. I'm Bob Edwards.
In recent years, many new or newly spreading illnesses have entered the popular vocabulary. AIDS, Hantavirus, Lyme disease and Ebola are on a growing list of so-called emerging infectious diseases. Scientists say the destruction of wilderness and the growth in international trade have helped spread pathogens to people worldwide. But the movement of infectious agents among continents and species harms more than just human beings. Ecologists say it poses a major threat to wildlife. NPR's David Baron reports.
DAVID BARON reporting:
Four years ago in a terrarium at the London Zoo, an animal species became extinct. It was a type of tree snail, about a half inch across, white with a brown tip. It used to live on an island in the South Pacific, but disruption of its ecosystem drove the snail to extinction in the wild. When the last animals in captivity died at the zoo, Peter Daszak investigated. Daszak, now an ecologist at the University of Georgia, found the snails had been killed by a previously unknown parasite. The discovery struck him as profound.
Mr. PETER DASZAK (University of Georgia): What we had was not only a parasite killing off a group of snails, it was a parasite killing off the last individuals of a species. Therefore, it was the first case of extinguishing by infection, extinction due to infectious disease that we know of, that we can definitively say.
BARON: Daszak decided to investigate if infectious diseases pose a similar threat to species in the wild. He and colleagues in Australia and England sifted through the scientific literature and identified dozens of emerging infectious diseases of wildlife, including avian malaria, crayfish plague and a kind of snake pneumonia. Daszak and his co-workers write in today's issue of the journal Science that weaving through these diseases is a common thread: people.
Mr. DASZAK: What shocked me was there are very few diseases that don't have some human, underlying anthropogenic cause.
BARON: For example, Daszak says, in Africa, wild dogs of the Serengeti have been sickened by infections spread by domestic dogs.
Mr. DASZAK: What happens is is people keep domesticated dogs close to wild dog habitat. There's a crossover of pathogens--canine distemper is one of them and rabies is the other--and these cause die-offs and eventually local extinction of the smaller wild dog population.
BARON: In the British Isles a few years ago, bird watchers noticed large numbers of finches dying. Tom Pennycott of the Scottish Agricultural College discovered that the birds had been killed by strains of salmonella and E. coli bacteria that they'd contracted at backyard feeders.
Mr. TOM PENNYCOTT (Scottish Agricultural College): It's very difficult to keep bird feeders clean. You get a buildup of droppings and that's where the organisms are to be found. So I think we certainly are contributing to what may be normally just a minor cause of mortality, we're making into a major cause of mortality by feeding the wild birds.
BARON: In the United States, an outbreak of West Nile virus that killed seven people in the New York City area last year also killed thousands of crows, as well as exotic birds at the Bronx Zoo. Public health officials believe the outbreak started when an infected person arrived in the US from Israel or Europe. The authors of the new study conclude that humans have so disrupted the global environment, transporting goods across oceans and mixing species that never co-existed, that wildlife diseases are spreading at an unprecedented rate.
Peter Daszak and his colleagues say the problem deserves to be recognized as an important environmental threat, and they've given it a name, pathogen pollution.
Mr. DASZAK: It's not a new form of pollution, but it's one that's been overlooked in the past. And I think that's probably a significant form of pollution. Certainly it does have very subtle and hidden effects that we're only just beginning to realize.
BARON: Daszak says in the same way federal scientists closely monitor human disease and try to head off outbreaks before they start, the government should do the same for wildlife diseases. Bob McLean agrees. He heads the National Wildlife Health Center, a federal agency in Madison, Wisconsin. McLean says government inspectors currently check imported animals for diseases of livestock and poultry. He says the same should be done for diseases of wildlife.
Mr. BOB McLEAN (National Wildlife Health Center): There's a lot of importation of animals, and wild animals seem to be now favored for the pet trade; as well now a lot of game farming, birds like ostriches and emus and a lot of mammals. Pathogens could be in the animals or could be carried on ticks that are on these animals. So we need to be more vigilant about that.
BARON: McLean says monitoring of wild animal diseases doesn't receive the kind of funding that's dedicated to diseases of farm animals and humans. But ecologists say in today's interconnected world where a virus of non-human primates can launch the AIDS epidemic, the distinction between emerging diseases of humans and animals gets blurrier all the time. David Baron, NPR News, Boston.