Prions - the infectious proteins that cause mad cow disease and its human version Creutzfeldt-Jakob disorder - could also be transmitted through the air, University of Zurich researchers have discovered.
The surprising finding will likely mean a whole new push of precautionary measures for scientific labs, slaughterhouses and animal feed plants.
Until now, it was assumed that prions could be transmitted by consuming food made from BSE-infected cows, through contaminated surgical instruments or blood transfusions but were not generally considered to be airborne like many viruses.
Creutzfeldt-Jakob disease is characterized by a progressive and invariably lethal breakdown of brain cells.
In the new study, Adriano Aguzzi and his team exposed mice to aerosols containing prions. Unexpectedly, it was found that inhalation of prion-tainted aerosols induced disease with frightening speed.
Exposure to the aerosols for just one minute was sufficient to infect all the mice.
The researchers noted that the longer the exposure, the shorter the incubation time in the recipient mice, after which they developed the clinical signs of a prion disease.
Surprisingly, the prions appeared to transfer from the airways and colonize the brain directly, since immune system defects - known to prevent the passage of prions from the digestive tract to the brain - did not prevent infection.
The precautionary measures against prion infections have not typically included stringent protection against aerosols.
Aguzzi recommended precautionary measures to minimize the risk of a prion infection but also emphasized that the findings stem from the laboratory conditions and that Creutzfeldt-Jakob patients do not exhale prions.
The findings are published in the journal PLoS Pathogens.