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Moving Beyond Mad Cow

Moving Beyond Mad CowAnemerging family of diseases including mad cow require a new approachto protecting the nation’s food supply as well as humanand animal populations. PulauTioman, Malaysia 

Medford/Somerville, Mass. [02.02.04] Deep inside northern Malaysia, Tufts graduate Dr. Jonathan Epstein and his colleagues are tracking the elusive and deadly Nipah virus - responsible for killing several hundred people in a swift outbreak several years ago. Like Mad Cow, West Nile, SARS and the Avain flu, Nipah seems to have sprung out of nowhere. But Epstein and his fellow scientists, dubbed "virus hunters," believe a new family of emerging diseases are leaping from animal populations to humans - posing a major environmental and public health threat.

"When we talk about wildlife diseases that jump into humans, it's a universal story," Epstein - who graduated from Tufts' School of Veterinary Medicine in 2002 - told CBS' 60 Minutes II. "It doesn't just happen in Malaysia with Nipah virus. It happens in China. It happens in North America."

One of Epstein's colleagues estimated that 75 percent of all emerging diseases in humans were originally passed from domestic or wild animals.

"With the increase in global travel, with the increase in trade, with the increase in human activities all over the world, the world's becoming a small place," said Epstein, a veterinarian who serves as senior program officer at the Wildlife Trust's Consortium for Conservation Medicine. "So just because there may not be Nipah virus in America right now doesn't mean that a similar virus can't emerge there, or that other unknown diseases can't pass from wildlife into people in America."

In December, the U.S. came face-to-face with that reality when mad cow disease surfaced on American soil for the first time. The beef industry scrambled to isolate the infected animals while beef exports ground to a halt.

While all known infected animals have been killed, Epstein says the family of viruses that infected them, called Prions, is much harder to eliminate.

"Prions are extremely hardy and persistent," Epstein and his colleagues and the Wildlife Trust wrote in a San Francisco Chronicle op-ed. Resistant to heat and detergents, they are very difficult to eradicate.

"The unusual nature of prions make them an insidious family of disease," wrote the Tufts graduate. "Environmental contamination may thus be a long-term mechanism for the spread of TSEs. It is not inconceivable that the prions that cause mad cow disease could spread environmentally."

That would pose significant problems for farmers who are trying to protect their animals and eliminate the diseases. As they dispose of the infected cows, for instance, farmers could be inadvertently spreading the disease via the environment.

"In the United Kingdom, mad cow-infected cattle were burned and buried, but now concerns are arising there about disease-causing prions reaching the water table," Epstein wrote. "How will cattle ranches dispose of the estimated 200,000 high-risk bovine carcasses each year, some of which may well contain TSE? If they are buried in whole or part, coyotes, mountain lions, wolves and other carnivores could eat contaminated tissue and spread the disease further."

If the diseases begin spreading among captive and wild animals, farmers will face steep challenges in protecting their livestock.

"It is possible that mad cow disease is already present in other cows, or that it can be transmitted between cows and wild deer," the Tufts graduate wrote in the Chronicle. "Environmental decontamination will become a critical issue for the beef industry, as ranches that test positive for mad cow disease will have to have techniques in place to clear the infection.

"While the policy steps are important in protecting humans from contaminated meat, they ignore the reality that mad cow disease is also very much an environmental issue," wrote Epstein. "We cannot afford to treat emerging diseases as if they start and stop within a single species or within a hospital or cattle ranch."

But there may be some good news. The solutions to many of these issues, Epstein says, may come from a new collaborative approach among a wide variety of experts who are researching these emerging diseases.

"By understanding some of the ecological factors that drive disease emergence, some of the factors like human activities that bring people closer to wildlife, that place stress on wildlife, that may make it more likely for these diseases to jump into humans, we hope to be able to apply these principles, in general, to other diseases and prevent future outbreaks," the Tufts graduate told 60 Minutes II.

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