Peter Daszak: Exploring Disease Pathways

Interviewed by Jim Motavalli

Peter Daszak is the executive director of the Consortium for Conservation Medicine (CCM), but he’s also a working scientist. His credits include identifying the first case of a disease causing the extinction of a species, discovering the connection between an amphibian-based fungal disease and the disappearance of frogs globally, and demonstrating the link between global trade and disease incidence in a process called "pathogen pollution."

A native of Britain, Daszak earned a Ph.D. in the parasites of poultry, "then got really interested in the effects of parasites on endangered species in conservation programs in zoos and in the wild. At first it was very difficult to find funding for that kind of work, but it has gotten better and better."

E Magazine: What is the specific mission of CCM?

We’re a think tank bringing together different scientific disciplines around the same table: medical sciences with veterinary sciences, ecology and conservation. We deal with challenges to human and ecosystem health from infectious diseases and pollution in an ecological context. We’ve gotten to the stage now where we know enough about conservation on one side, and about how infectious diseases work on the other, to really start to mix the two together.

The Consortium grew out of the Center for Conservation Medicine at Tufts University in Boston. We’ve added some partners and moved the headquarters to Wildlife Trust. We"ll soon be celebrating 10 years of working on conservation medicine.

You’re working to keep West Nile out of Hawaii and the Galapagos Islands. Are those two different challenges, or the same challenge?

It’s the same challenge with differences in approach and urgency. It gets at the way conservation medicine works: instead of developing a vaccine after an outbreak occurs, we’re saying we can work ahead of the curve and predict the way diseases are going to emerge.

With West Nile, there’s a lot of vaccine work going on, but nobody’s dealing with it as a policy thing—can we prevent it from spreading? It’s in California now, and it’s already knocking on Hawaii’s door. If it reaches the islands it will be devastating. It’s a nasty disease, and there are going to be deaths. So we went to Hawaii and got in touch with the federal agencies that deal with transportation and tourism. Surely we can bring in some measures that will prevent mosquitoes from hitching a ride in the cargo hold of airplanes. We’ve also looked at cruise ships.

In the Galapagos, the threat is a bit different. We know West Nile is in Mexico, where it has caused large dieoffs in crocodile farms, and it’s moving down through the Caribbean. It will almost certainly reach South America next year or the year after. Once it gets to Ecuador, it will then get to the Galapagos via air travel. The Galapagos have some fantastic, unique bird species that are a keystone of evolutionary biology, such as Darwin’s finches. Also at risk are the flightless cormorants and Galapagos penguins. What a tragedy if it gets into those populations.

Does the new mobility of human populations play a role? What about sheer human density?

Most viruses are pretty good at moving from one individual to another in a population. That’s what they’re designed to do. Some viruses can also jump species pretty easily. A great example is canine distemper, which killed lions in the Serengeti, infected seals in Antarctica and black-footed ferrets in the American Southwest. Now we have a huge increase in contact between animals and humans, partly through the processes of deforestation and urbanization. Somebody building a road through the rainforest in Brazil is allowing viruses to get into the human population, and from there into global circulation.

Look at HIV/AIDS. It’s now pretty clear that it originated from bushmeat hunting in Africa. Once the disease established itself in humans, it started traveling around the world. SARS moved from animals in a Chinese food market to the global population within a few months, closing down Montreal. The denser the human population, the easier it is to spread. With an unprecedented level of travel and trade, we’re going to see more and more of these viruses emerge from obscure and difficult-to-predict species of wildlife. There are whole new pathways for diseases to travel, and a new suite of environmental changes that increase the contact between us and wildlife pathogen reservoirs.

Are you seeing more recognition of conservation medicine as an important science?

In the last few years it has really begun to take off. If you go to meetings you see the enthusiasm among young ecologists who are realizing the significance of pathogens. Take the huge boom-and-bust population cycles in some wildlife species. The loss of red grouse in England, for example, is not caused by overgrazing as was supposed, but by a parasite. And also in England, the native red squirrel has gradually been pushed out of its habitat by the gray squirrel from North America. The story had been that these big, bulky gray squirrels simply bullied the red squirrels. That naéve explanation has been shunted aside by a clear disease hypothesis: The gray squirrel carries a virus that kills red squirrels, driving them to extinction.