Down With the Sickness

On an airport runway in Hawaii last fall, a sparrow nearly became a canary. State officials testing captured birds got one positive result for the West Nile virus, which had yet to arrive from the mainland. Hawaii and Alaska remain the only states in the U.S. that haven't had cases of this rapidly spreading global disease -- which has infected more than 16,000 people and killed more than 650 in the U.S. since it first appeared in New York City in 1999 -- and they're anxious to keep it that way. When further tests on the sparrow came back negative, scientists and doctors who had been working together to keep the mosquito-borne virus away from the Aloha State's people and native birds breathed a sigh of relief. "Once one mosquito slips through," said one researcher, "it will be only a matter of days before West Nile is all over the island."

A year before that scare, researchers studying several U.S. deaths from hantavirus -- a disease transmitted to humans through mouse saliva, feces, or urine -- pinned it on climate issues. A six-year drought in the Southwest had affected natural predators of the deer mouse, they concluded, contributing to a boom in the mouse population, which increased human exposure and helped trigger the lethal outbreak. They added, "It is not known how many viruses or other infectious agents in the environment, potentially harmful to man, are being held in check by the natural regulation afforded by biodiversity."

In other words, the delicate web of species that we value so highly -- and disrupt so frequently -- is quietly helping to protect our health. It's not a new idea, but it's a threatened truth taking on ever more urgency. On our incredible shrinking planet, a bold mouse or a busy mosquito can make hundreds of people sick. And in a new global collaboration, a growing cadre of scientists, public-health officials, veterinarians, and physicians is working together to understand new patterns of destruction and disease -- and to do their best to keep us well.

Knowing Me, Knowing You

In the 19th century, health-care practitioners were expected to have training in the natural sciences; the dictum turned out such well-rounded students as Charles Darwin. But specialization in the 20th century drove the two fields apart. Today, doctors rarely talk to veterinarians, and neither has much interaction with wildlife biologists. Conservation medicine (or "ecological medicine") is an attempt to bring them back together.

"We need to get the vets out of the barn," says Mark Pokras of the Tufts University School of Veterinary Medicine. "We need to change the mind-set of all the groups -- vets, physicians, scientists, conservation biologists, environmentalists -- to be more broadminded and visionary."

To accomplish that goal, conservation medicine needs a well-organized champion, able to synthesize vast amounts of new scientific data from disparate sources. Enter Wildlife Trust.

The Trust, based in Palisades, N.Y., is not just the "go to" organization on conservation medicine; it virtually launched the discipline. In 1997, it cofounded the Consortium for Conservation Medicine (CCM) with Harvard Medical School's Center for Health and the Global Environment and Tufts University's Center for Conservation Medicine. CCM, which the Trust houses and administers, works to understand the connections between animals, humans, and emerging diseases. From the Rocky Mountains to Rwanda, it conducts research on infectious diseases, pathogen pollution, climate change, marine systems, and endangered species, bringing together teams of physicians, vets, ecologists, wildlife epidemiologists, and public-health officials. The consortium also works with veterinary and medical students and promotes conservation medicine at workshops and conferences, as well as to policy makers.

Down the road, Wildlife Trust President Mary Pearl envisions master's programs that would offer public-health scientists and wildlife biologists a certificate in conservation medicine; she wants to see public health departments hiring veterinarians, and park systems hiring public-health officials. "We need an arsenal of public officials, increasing our observation of sentinel species to find hot spots of new disease emergence," she says.

While still a small field, conservation medicine is gaining recognition from mainstream funding sources such as the National Science Foundation, the World Bank, the National Institutes of Health, and private foundations. "For too long, the environmental movement has been perceived as an elitist, esoteric pleasure for the well-to-do who want to preserve scenic landscapes and don't have to concern themselves with real problems," says Pearl, an editor of the book Conservation Medicine. "[This field] demonstrates how healthy ecosystems are the basis for human well-being, and it can really engage people who didn't see the relevance before."

Weapons of Mouse Destruction

In Malaysia, workers on a pig farm become sick with a virus transmitted by the porkers -- a virus that originally came from bats. In Peru, forest clearing results in an explosion of malaria-bearing mosquitoes. In Rwanda, measles and giardia run rampant through the local population of mountain gorillas, animals that are a favorite with tourists.

Three quarters of all emerging diseases are "zoonotic," shared by animals and humans. West Nile and hantavirus are well-known examples; others include monkeypox, HIV, avian influenza, Ebola, Lyme disease, and SARS. "Diseases are moving from animals to humans and from one animal species to another at an alarming rate," says Lee Cera, a veterinarian at the Loyola University Chicago Stritch School of Medicine and a principal with the Conservation Medicine Center of Chicago. "When I went to school we were told, 'This disease won't go from a dog to a cat.' Then all of a sudden a dog virus decimated the lions of the Serengeti. How did it happen? When did it happen?"

Conservation medicine aims to answer these questions. At the heart of the problem is the usual suspect: humans. Loss of animal habitat and increasing human incursion into wilderness areas, often spurred by human population growth, set up new points of contact. International trade in exotic species breaks down barriers. Climate change causes species migration. Global travel, including ecotourism (which emphasizes wilderness visits), can move exotic jungle viruses into the modern world, as dramatically documented in Richard Preston's best-selling book The Hot Zone. In 1950, 3 million people a year flew on commercial jets; by 1990, 300 million did. Two million people cross international borders every day, many carrying agricultural products, animals, soil, ballast water -- and disease-causing microbes.

"Most viruses are pretty good at moving from one individual to another in a population; that's what they're designed to do," says Peter Daszak, executive director of CCM. "Some viruses can also jump species pretty easily. A great example is canine distemper, which killed lions in the Serengeti and 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." Daszak adds: "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."

Laurie Garrett, author of The Coming Plague: Newly Emerging Diseases in a World Out of Balance, writes that in the post-World War II environment, powerful medical weaponry (antibiotics, vaccines, water treatment, anti-malaria drugs) gave scientists confidence that they could eradicate infectious disease from viral, bacterial, or parasitical sources. In 1900, nearly 800 Americans out of every 100,000 died each year of infectious disease. By 1980, the number was down to 36 per 100,000. The World Health Organization's "Health for All" accord, signed in 1978, set a goal of preventing and controlling many international scourges by 2000. But amid all this optimism, the numbers started rising; in 1995, it was 63 people per 100,000.

"The grandiose optimism rested on two false assumptions," Garrett wrote in the journal Foreign Affairs, "that microbes were biologically stationary targets, and that diseases could be geographically sequestered." Scientists, she wrote, "have witnessed an alarming mechanism of microbial adaptation and change ... Anything but stationary, microbes and the insects, rodents, and other animals that transmit them are in a constant state of biological flux and evolution."

Flux, you say? Let's talk global warming. The congressionally mandated "National Assessment of Climate Change and Health," issued in 2001, foresaw greater incidence of heat stroke, malaria, yellow fever, and respiratory disease as a result of global warming. As countries like the U.S. become more "tropical," it said, insect- and rodent-borne diseases may be seen more often. That same year, the American Journal of Public Health reported that 68 percent of waterborne disease outbreaks studied came after major precipitation events, which are predicted to occur more frequently because of global warming. Drought is just as bad, drying up flowing rivers and leaving stagnant water, a mosquito-breeding haven.

"As we encroach on and modify natural habitats, these outbreaks will increase," says Richard Ostfeld of the Institute of Ecosystem Studies. "The evidence is very convincing that we're engaging in risky behavior. We need the political will to change how we modify the environment. I'm hopeful that we can stop habitat destruction, because if we reduce habitat fragmentation there's an immediate positive effect. Disease risk can be reduced in decades."

Paging Doctor Green

Like any medical issue, these are not simple. Sometimes they are decidedly unglamorous. For instance, CCM has met with key health and military officials in Hawaii to discuss preventing West Nile. Although they encountered support, "it's a difficult agenda to push proactively," says Daszak. "If we're successful, nothing happens."

And the road to making nothing happen is paved with complexities. For instance: an oft-touted fix for malaria -- one of the diseases WHO expected to be eradicated by now -- is DDT. Some argue that the chemical, whose dangers were illuminated in Rachel Carson's Silent Spring and have been debated in these pages, need not create environmental disasters if used in low-volume, localized indoor spraying. Its long-lasting power makes it the most cost-effective treatment, experts say. Although banned in the U.S., DDT is still produced in other countries, and WHO has designated it acceptable for certain public-health uses.

Then there's the question of funding. According to author Garrett, the World Bank replaced WHO as the world's largest public-health funder by 1997. But this is the same World Bank that provides $2.5 billion in loans for nonrenewable energy projects, most of them based around global warming-aggravating fossil fuels. Since WHO estimates that 160,000 people die annually because of the effects of climate change, these loans are very much a health issue.

There's also the risk of demonizing animals, says Pearl, which could lead to calls for extermination. "We've found over and over again that when a species is eliminated, there are unanticipated consequences," she says. "Every organism is not harboring just one virus or just one parasite. So by eliminating a carrier species, we may unwittingly be encouraging another virus to look for a new livestock or human host. We have to see the full picture ... We can't play games with ecosystem dynamics, and we can't kill a hydra by cutting off only one of its heads."

Meanwhile, the issue underlying every part of conservation medicine is the challenge its practitioners face in working together. This includes literally learning to speak the same language; the word "ecosystem," for example, has different meanings for the different groups. But in the face of constantly emerging diseases in an increasingly interconnected world, those involved agree it's necessary.

"We see the world in a different way," Tufts' Pokras acknowledges. "It's like the five blind men and the elephant. But we need to overcome this problem, because conservation on a global scale is so complex ... no one group has the knowledge, skills, and perspective to grasp it all and [find] solutions."

This is an excerpt from a longer article published in E Magazine; the full article can be found here.