SCIENCE DAILY: INFECTION from AIRBORNE PRIONS.

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[4] Airborne transmission (mice)
Date: 14 Jan 2011
Source: Science Daily [edited]
<http://www.sciencedaily.com/releases/2011/01/110113213056.htm>


New findings suggest airborne pathogens can induce mad cow disease
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Airborne prions are also infectious and can induce mad cow disease or
Creutzfeldt-Jakob disorder, new findings suggest. This is the
surprising conclusion of researchers at the University of Zurich, the
University Hospital Zurich, and the University of Tuebingen. They
recommend precautionary measures for scientific labs, slaughterhouses,
and animal feed plants. The prion is the infectious agent that caused
the epidemic of mad cow disease, also termed bovine spongiform
encephalopathy (BSE), and claimed the life of over 280 000 cows in the
past decades. Transmission of BSE to humans, such as, by ingesting
food derived from BSE-infected cows, causes variant Creutzfeldt-Jakob
disease, which is characterized by a progressive and invariably lethal
break-down of brain cells.

It is known that prions can be transmitted through contaminated
surgical instruments and, more rarely, through blood transfusions. The
consumption of food products made from BSE-infected cows can also
induce the disease that is responsible for the death of almost 300
people. However, prions are not generally considered to be airborne --
in contrast to many viruses including influenza and chicken pox.

Prof Adriano Aguzzi's team of scientists at the universities of
Zurich and Tuebingen and the University Hospital Zurich have now
challenged the notion that airborne prions are innocuous. In a study,
mice were housed in special inhalation chambers and exposed to
aerosols containing prions. Unexpectedly, it was found that inhalation
of prion-tainted aerosols induced disease with frightening efficiency.
Just a single minute of exposure to the aerosols was sufficient to
infect 100 per cent of the mice, according to Prof Aguzzi who
published the findings in the Open-Access-Journal "PLoS Pathogens."
The longer exposure lasted, the shorter the time of incubation in the
recipient mice and the sooner clinical signs of a prion disease
occurred. Prof Aguzzi says the findings are entirely unexpected and
appear to contradict the widely held view that prions are not
airborne. The prions appear to transfer from the airways and colonize
the brain directly because immune system defects -- known to prevent
the passage of prions from the digestive tract to the brain -- did not
prevent infection.

Precautionary measures against prion infections in scientific
laboratories, slaughterhouses, and animal feed plants do not typically
include stringent protection against aerosols. The new findings
suggest that it may be advisable to reconsider regulations in light of
a possible airborne transmission of prions. Prof Aguzzi recommends
precautionary measures to minimize the risk of a prion infection in
humans and animals. He does, however, emphasize that the findings stem
from the production of aerosols in laboratory conditions and that
Creutzfeldt-Jakob patients do not exhale prions.

Reference
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Haybaeck J, Heikenwalder M, Klevenz B, et al: Aerosols Transmit
Prions to Immunocompetent and Immunodeficient Mice. PLoS Pathog. 2011;
7(1): e1001257. DOI:10.1371/journal.ppat.1001257;
<http://www.plospathogens.org/article/info%3Adoi%2F10.1371%2Fjournal.ppat.1001257>