Mary Pearl

Protection of the environment often seems like a low-priority issue when stacked up against more immediate concerns. But a healthy environment is no mere luxury, says Mary Pearl, president of the Wildlife Trust. It is a prerequisite for human health. Pearl and her colleagues spearheaded the development of "conservation medicine"--a scientific exploration of the links between the health of humans, wildlife and eco-systems. Among the trust's current projects: a collaboration to monitor the spread of avian flu among wild birds and research uncovering the origin of SARS. Pearl spoke recently with newsweek's Anne Underwood. Excerpts:

PEARL: It's an approach that evolved from the recognition of a crisis--namely, unprecedented levels of disease, driven byhuman-induced environmental degradation. Since the mid-1970s, more than 30 new diseases have emerged, including AIDS, Ebola, Lyme disease and SARS. Most of these are believed to have moved from wildlife to human populations. Yet no one was getting a grip on the totality of the picture. Damaged ecosystems--characterized by toxins, degradation of habitat, removal of species and climate change--create conditions for pathogens to move in ways they wouldn't normally move.

How so?

The destruction of the Peruvian rain forest, for example, has led to an explosion of malaria-bearing mosquitoes that thrive in sunlit ponds created by logging operations. Even a 1 percent increase in deforestation leads to an 8 percent increase in mosquitoes, according to Jonathan Patz at the University of Wisconsin.

Does the wild-animal trade play a role in the spread of disease?

You never import just one species. You import the animal and all its parasites and pathogens. A few weeks ago the British government identified the deadly H5N1 strain of bird flu in an imported parrot that was being held in quarantine. But half the wildlife trade is illegal, so it's not even being monitored.

Live-animal markets are also a concern. We recently learned that SARS originated in the Chinese horseshoe bat. The bats live in remote caves, but merchants in China brought them into live-animal markets, choppeed them up on the same cutting boards used for poultry and didn't wear gloves or masks. That was a recipe for the disease to spread to humans, who normally would not come into intimate contact with bats.

What led you to suspect the horseshoe bat in the first place?

Jonathan Epstein, our field scientist on the case, was looking at bat populations because of Nipah virus--a deadly virus that emerged in humans in Malaysia in 1999. Nipah virus is harmless in fruit bats, but in people it causes a high fever, brain inflammation, seizures and death. It emerged in pig farms in formerly forested areas, when it passed from bats to pigs and then to farmers. The Malaysian government moved quickly to shut down those pig farms. Subsequently there have been outbreaks in Bangladesh, so it will be important to continue monitoring fruit bats.

So the answer isn't to kill bats, but to change our behavior?

It's not bats that are to blame. Disease agents are all around us; they're part of the natural world. It's our behavior that creates the circumstances for these disease agents to move from animals into human populations.

How does this relate to avian flu?

Again, it's a situation where wildlife disease has moved into the human sphere, this time through wild birds' sharing habitat with domestic birds. We're increasingly substituting ourselves and our livestock for the animals that would be the natural reservoirs of disease-causing agents.

We recently learned that the 1918 flu, which killed up to 50 million people worldwide, was an avian virus that jumped to humans. In the context of the current bird flu, does that worry you?

The avian flu is not new. Most forms of the disease are harmless to us and no more than a nuisance to birds. But it's a highly evolving group of viruses--and the wild birds that carry it are migratory, unlike most bats, so when a deadly flu emerges in these birds, it has the potential to spread rapidly. That's why you need good surveillance, to identify points of transmission. Then you can be hypervigilant in looking at poultry farms in those areas for signs of disease.

In October the [U.S.] Senate introduced an amendment on avian-flu preparedness. I was really happy to see, for the first time, money in those appropriations for migratory-bird surveillance. This is the first time Congress has recognized the importance of wildlife-disease dynamics in the spread of human disease.

If humans create the conditions for new diseases, can we also help suppress them?

Absolutely. I foresee the time when departments of public health will have conservation-medicine specialists. It's rare for diseases to jump between species. But we can look for hot spots in landscapes, where problems are likely to arise.

Mary Pearl | News
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