Pet Trade Introduces Diseases, Costs

April 30, 2009 -- Invasive species are putting major strains on our environment, our pocketbooks and our health, new studies suggest, and our nation's demand for exotic pets may be to blame.

The wild animal trade may even be upping our risk for diseases like the current outbreak of swine flu.

Between 2000 and 2006, the United States imported nearly 1.5 billion live animals from 190 countries, mostly for sale as pets, according to a paper published today in the journal Science. Eighty percent of those animals came from wild populations. And nearly 70 percent of them came from Southeast Asia, a known hotspot for emerging diseases that, like the swine flu, can jump from animals to people.

Once invasive species have escaped into the environment, they can cause a cascade of problems that are expensive to fix. In another paper, published last week in Frontiers in Ecology and the Environment, European researchers found that controlling an invasive species, can cost $10 million or more.

"That's what hits home," said Katherine Smith, a conservation biologist at Brown University in Providence, Rhode Island. "Money and disease."

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Smith and colleagues analyzed U.S. Fish and Wildlife Service records of animal shipments made between 2000 and 2006. Of the nearly 1.5 billion creatures brought in during that time, they found, 92 percent were sold as pets. The rest were imported for research, education, zoos, and other reasons.

Most imported animals were tropical and freshwater fish, but the list also included reptiles, amphibians, mammals, even coral. Besides the sheer number of animals brought in, the researchers were shocked by how incomplete the data was. Many orders were labeled simply "marine fish" or "live invertebrate." Only 13 percent of shipments were identified by species.

"It was impossible to assess the full diversity of animals," Smith said. "Even more frightening, we couldn't begin to think about their risk as invasive species or as animals bringing in diseases."

Those impacts can be serious. In Florida in the early 1990s, for example, a number of pet Burmese pythons escaped their outdoor enclosures during a major hurricane. Today, some 30,000 of the snakes, which can grow up to 20 feet long, live in the Everglades. There, the voracious predators are eating wildlife, including some endangered species, and competing with the American alligator, the region's native top predator. Fish and wildlife officers have told one story of a dramatic wrestling match between a python and an alligator.

In another example in 2003, a shipment of giant Gambian rats came to the Midwest infected with monkeypox. The disease jumped to prairie dogs that ended up as pets in a home where they spread the illness to their human owners and led to 72 human cases.

The CDC identified and controlled the problem quickly, but the consequences could have been disastrous if the prairie dogs had been released into the wild, Smith said. Such close calls and near misses are especially concerning in light of other emerging diseases, Smith said, including the swine flu.

Her team recommended that animals be screened for high-priority diseases before we let them cross borders and that public educational campaigns be intensified so that pet-owners can make wiser decisions about the types of animals they bring home, among other protective measures.