BSE in the Air?

Prions, the infectious proteins that cause lethal neurological diseases such as bovine spongiform encephalopathy (BSE) in cows and variant Creutzfeldt-Jakob disease (CJD) in humans, can be transmitted in aerosol form, according to new research conducted by a team of scientists from the University of Zurich in Switzerland and the University of Tübingen in Germany (Haybaeck J, Heikenwalder M, Klevenz B, et al. Aerosols transmit prions to immunocompetent and immunodeficient mice. PLoS Pathog. 2011;7(1): e1001257.)

In the past, it was thought that prions were not airborne. Most of the approximately 300 cases of transmission of BSE to humans (in the form of Creutzfeldt-Jakob) have been the result of eating meat from BSE-infected cows. Prions can also be transmitted through contaminated surgical instruments and, more rarely, blood transfusions.

But when Adriano Aguzzi, MD, PhD, of the University Hospital Zurich, and his team aerosolized prions and exposed mice to the inhaled agents, just one minute of exposure was enough to infect 100% of them. “The longer exposure lasted, the shorter the time of incubation in the recipient mice and the sooner clinical signs of a prion disease occurred,” Dr. Aguzzi says.

“These results suggest that current biosafety guidelines applied in diagnostic and scientific laboratories ought to include prion aerosols as a potential vector for prion infection,” wrote the scientists.

But don’t panic just yet, said Jeff Bender, DVM, MS, director of the Center for Animal Health and Food Safety at the University of Minnesota. “The study is focused on a mouse-adapted strain of prion and immunodeficient mice,” he says. “Those aren’t real-world situations that people working in slaughterhouses would be exposed to.”

Epidemiologically speaking, Bender said, there is no evidence that people working in diagnostic labs, feed plants, or slaughterhouses are at greater risk for CJD. “But it does bring up a good point that prions can be transmitted in different ways. Any time you’re working with nervous tissue, you should be wearing a barrier, such as gloves, and if you’re cutting brains, you probably need a face shield. But any precautions taken will have to be practical,” he added.

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