- Airborne Prion Transmission (mice)
- Date: 14 Jan 2011
- Source: Science Daily
- http://www.sciencedaily.com/releases/2011/01/110113213056.htm
-
- New findings suggest airborne pathogens can induce mad
cow disease
- ------------------------------------------------------------------
- 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 --------- 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>
-
- Abstract: Prions, the agents causing transmissible spongiform
encephalopathies, colonize the brain of hosts after oral, parenteral, intralingual,
or even transdermal uptake. However, prions are not generally considered
to be airborne. Here we report that inbred and crossbred wild type mice,
as well as tga20 transgenic mice overexpressing PrPC, efficiently develop
scrapie upon exposure to aerosolized prions. NSE-PrP transgenic mice, which
express PrPC selectively in neurons, were also susceptible to airborne
prions. Aerogenic infection occurred also in mice lacking B- and T-lymphocytes,
NK-cells, follicular dendritic cells, or complement components. Brains
of diseased mice contained PrPSc and transmitted scrapie when inoculated
into further mice. We conclude that aerogenic exposure to prions is very
efficacious and can lead to direct invasion of neural pathways without
an obligatory replicative phase in lymphoid organs. This previously unappreciated
risk for airborne prion transmission may warrant re-thinking on prion biosafety
guidelines in research and diagnostic laboratories.
-
- Author summary: Prions, which are the cause of fatal
neurodegenerative disorders termed transmissible spongiform encephalopathies
(TSEs), can be experimentally or naturally transmitted via prion-contaminated
food, blood, milk, saliva, feces, and urine. Here we demonstrate that prions
can be transmitted through aerosols in mice. This also occurs in the absence
of immune cells as demonstrated by experiments with mice lacking B-, T-,
follicular dendritic cells (FDCs), lymphotoxin signaling, or with complement-deficient
mice. Therefore, a functionally intact immune system is not strictly needed
for aerogenic prion infection. 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.
-
- --
- communicated by:
- Terry S Singeltary Sr
- flounder9@verizon.net
-
- Despite the perceived risk revealed by these experiments
with laboratory mice there has been no evidence to date linking prion disease
to employees in slaughterhouses, animal feed plants, or research laboratories.
- Mod.CP
-
- ******
-
-
- [5] Milkborne Prion Transmission (sheep)
- Date Thu 20 Jan 2011
- Source: Science Daily [edited]
- http://www.sciencedaily.com/releases/2011/01/110119191350.htm
-
-
- Prion disease spreads in sheep via mother's milk
- ------------------------------------------------
- Transmission of prion brain diseases such as bovine spongiform
encephalopathy (BSE) -- also known as mad cow disease -- and human variant
Creutzfeldt-Jakob disease (vCJD) is generally attributed to the consumption
of the brain or organ meat of infected animals but new research demonstrates
lambs exposed to milk from prion-infected sheep with inflamed mammary glands
can develop prion disease as well. The research, which is published in
the January 2011 issue of the Journal of Virology, has major implications
for human and livestock health.
-
- "Prions cause devastating, ultimately fatal infections
in humans," says corresponding author Christina Sigurdson of the University
of California, San Diego School of Medicine. "This study is the 1st
demonstration of prions from an inflamed organ being secreted, and causing
clinical symptoms in a natural host for prion disease."
-
- Recent research had suggested that human-to-human transmission
of prions has occurred via blood transfusions, "underscoring the importance
of understanding possible transmission routes," the researchers write.
The misfolded prions that cause vCJD in humans, and BSE in cattle -- which
can be transmitted to humans -- commonly accumulate in lymphoid tissues
before invading the central nervous system, where they wreak their deadly
effects. Inflammation can cause lymphoid follicles to form in other organs,
such as liver and kidney, which leads prions to invade organs that normally
do not harbor infection. In recent research, this team, led by Ciriaco
Ligios of the Istituto Zooprofilattico Sperimentale in Sardinia, Italy
and Adriano Agguzi at the University of Zurich, Switzerland, reported sheep
with misfolded prions in inflamed mammary glands, also known as mastitis,
raising concerns that prions could be secreted into milk.
-
- In the new research, the team infected sheep with a common
retrovirus that causes mastitis, and misfolded prions. They bred the sheep,
in order to stimulate the females to produce milk, which they then collected
and fed to lambs that had never been exposed to prions. The lambs developed
prion disease after only 2 years, a speed which surprised the researchers,
and "suggested that there was a high level of prion infectivity in
milk," says Sigurdson.
-
- The research raises several disturbing possibilities.
- A common virus in a sheep with prion disease can lead to prion contamination
of the milk pool and may lead to prion infection of other animals. - The
same virus in a prion-infected sheep could efficiently propagate prion
infection within a flock, through transmission of prions to the lambs,
via milk. This might be particularly likely on factory farms, where mastitis
may be common, and could occur in goats as well as sheep. - Humans with
variant Creutzfeldt-Jakob disease might accumulate prions in inflamed organs,
and could also secrete prions.
-
- However, "this work cannot be directly extrapolated
to cattle," says Sigurdson. She says that BSE prions do not accumulate
to detectible levels in lymphoid organs, and thus would not be expected
to accumulate with inflammation. "Nonetheless," she says, "it
would be worth testing milk from cattle with mastitis for prions as there
may be other cellular sources for prions entry into milk."
-
- Reference
- ---------
- Ligios C, Cancedda MG, Carta A, et al: Sheep with Scrapie
and Mastitis Transmit Infectious Prions through the Milk. J Virol. 2011
Jan; 85(2):1136-9. Epub 2010 Nov 17. DOI:10.1128/JVI.02022-10; http://jvi.asm.org/cgi/content/abstract/85/2/1136.
-
- Abstract: Prions are misfolded proteins that are infectious
and naturally transmitted, causing a fatal neurological disease in humans
and animals. Prion shedding routes have been shown to be modified by inflammation
in excretory organs, such as the kidney. Here, we show that sheep with
scrapie and lentiviral mastitis secrete prions into the milk and infect
nearly 90 per cent of naive suckling lambs. Thus, lentiviruses may enhance
prion transmission, conceivably sustaining prion infections in flocks for
generations. This study also indicates a risk of prion spread to sheep
and potentially to other animals through dietary exposure to pooled sheep
milk or milk products.
-
- --
- communicated by:
- Terry S Singeltary Sr
- flounder9@verizon.net
-
- These research confirms experimentally previous observations
by others (such as, Lacroux C et al: Prions in Milk from Ewes Incubating
Natural Scrapie. PLoS Pathog 4(12): e1000238. doi:10.1371/journal.ppat.1000238;
-
-
- http://www.plospathogens.org/article/info%3Adoi%2F10.1371%2Fjournal.ppat.1000238
-
-
- Despite the potential risk of prion spread to other animals
through dietary exposure to pooled sheep milk or milk products none has
been observed so far.
-
- Perhaps of greater interest is the comment that humans
with variant Creutzfeldt-Jakob disease might accumulate prions in inflamed
organs, and could also secrete prions.- Mod.CP]
-
- Patricia A. Doyle DVM, PhD Bus Admin, Tropical Agricultural
Economics Univ of West Indies Please visit my "Emerging Diseases"
message board at:http://www.emergingdisease.org/phpbb/index.php Also
my new website: http://drpdoyle.tripod.com/ Zhan le Devlesa tai
sastimasa Go with God and in Good Health
-
- Benjamin Franklin said, "They that can give
up essential liberty to obtain a little temporary safety deserve
neither liberty nor safety."
|