earth talk 5-5-05
Dear “Earth Talk”: I recently heard the
term “conservation medicine.” What does it mean?
— Steve Falbo, San Francisco
Conservation medicine (sometimes called “conservation health”) is a relatively new field of research that studies the links among human health, animal health, and the environment. One of its major fields of study is the emergence in recent decades of deadly diseases that have crossed over from animals to humans, including “mad cow,” AIDS, Lyme disease, SARS, avian flu, and West Nile disease. Many of these plagues arose from some form of contact between human beings and animals in compromised ecosystems.
In 1998, for example, a previously unknown virus spread among farm families in Malaysia, eventually killing more than 100 people. The outbreak was traced back to a pig farm, where horses, cats, dogs and goats were also infected. The virus, named Nipah for one of its first human victims, eventually spread to Singapore, where nine slaughterhouse workers became ill after processing Malaysian pork.
Scientists deduced that the virus came from fruit bats that descended on Malaysia after their native habitat, forests in nearby Borneo and Sumatra, were clearcut. The bats sought refuge in the fruit trees hanging over the animal pens at the pig farm and passed the virus to the pigs by dropping infected fruit into the pens, where the pigs eagerly ate it. How the virus jumped to human beings is still a mystery, but scientists are quite sure that the clearing of forests in Borneo and Sumatra led indirectly to more than 100 human deaths.
“Diseases are moving from animals to humans and from one animal species to another at an alarming rate,” says Lee Cera, a veterinarian at Loyola University’s Stritch School of Medicine. “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 wiped out the lions of the Serengeti. How did it happen? When did it happen?” Conservation medicine is an attempt to answer these questions by bringing together professional fields that had previously worked in isolation: human medicine, veterinary medicine, infectious-disease research, public health, and environmental science.
Many factors are already understood. Increased human forays into wilderness areas (often spurred by population growth) have set up new points of human-animal contact. The international trade in exotic species also breaks down barriers. Climate change causes species to migrate to new areas, bringing with them new germs. Global travel plays a role: In 1950, 3 million people flew on commercial jets; in 1990, 300 million did. Two million people cross international borders daily, carrying with them huge amounts of agricultural products, live animals, soil, and disease-causing microbes.
The Wildlife Trust and the Consortium for Conservation Medicine are two organizations, both based in New York, at the forefront of this new field: “Conservation medicine demonstrates how healthy ecosystems are the basis for human well-being,” says Dr. Mary Pearl, the Wildlife Trust’s president, “and it can really engage people who didn’t see the relevance before.”
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