This is mostly a test ;) I want to see if this actually DOES embed the powerpoint into the post, since there isn't an "embed" button on my blogger dashboard that I can see...
Here is the readings for the slides:
I'm going to talk about prions today. First off, there
isn't really a consensus in the pronunciation - some say prions and some say
"pree-ons" so sorry if I confuse you!
Prions are a misfolded protein found on many cell membranes,
particularly nervous system tissue. we aren't sure exactly what is usually
does. The normal configuration is referred to as PrPc (cellular). The misfolded
configuration PrPsc (scrapie) where the structure alters from alpha helices
into beta sheets that pack tightly together into amyeloid aggregates that
disrupt the cell function and interfere with tissue function. The ends of the
aggregates are fibrils, which contact adjoining prion proteins and trigger this
post-translational rearrangement and add them to the aggregate.
Prion-based diseases are not curable and are fatal.
Because of the affinity of the prion protein for neural tissue, the diseases
are all neurodegenerative. Scrapie has been the bane of livestock farmers since
at least the 1700’s, all they really knew was that it was incredibly
infectious. Transmissible spongiform encephalopathy, or TSE, also known as mad cow
disease, emerged in the 1980’s in Great Britain, where some infected sheep
parts were rendered into cattle meal which infected the cows, and when the beef
was eaten, it then infected people and eventually was strongly linked to sudden
increased emergence of the variant Cruetzfeldt-Jakob disease. Chronic wasting
disease, CWD, is the disease affecting
the cervid family – deer, moose, and elk. This was my
research focus. There are also other prion based diseases.
CWD was first identified in Colorado in 1967 but now
is found in 23 states and Canada, in
wild populations and deer farms. Like other prion-based
diseases, CWD has an incubation
time after
infection from 18 months to over 20 years. During this phase, the deer may display
muscle wasting, excessive salivation, and weight loss. Near the end, the acute clinical
phase develops, asts around 2-6 months and includes hyper-excitibility,
abnormal behavior, loss of bodily functions, and eventually death.
Transmission - Only cells that can express the PrP
protein can become infected. Researchers have studied transmission routes.
Plant leaves can become infected from direct contact with prions or plant root
uptake from infected soil. After infection, even before the onset of the acute
clinical phase, the deer shed infectious prion particles into the environment.
Once death occurs, the body contains a large volume of infectious prions that
can be carried to water sources via runoff, or contaminate the soil when the
body decomposes. Contaminated water can also come from slaughtering facilities.
Ecto-parasites such as certain fly larvae and mites can transmit prions from
one species to another.
Holcomb et al, 2016, used computer modeling to determine
the volume of shedding from infection until death from saliva, urine, and
feces. it predicted that one lethal dose around 9 months post-infection
increased drastically by 15 months, to over 10 lethal doses.
Prions are notoriously difficult to eradicate from
surfaces or to disinfect tissue. The prion in tissue has found to still be
viable at 600 degrees Celsius. And of course, removing plants, soil, water, and
ecto-parasites from infected pasture, fields, or forests is almost impossible.
The World Health Organization recommendations from 1997 only include “Variable
or partially effective” methods. I assume if they had better suggestions, they
would have updated this information.
But, there are researchers investigating prion
treatments. Ding and his associates have done many ozone treatment studies.
Because prions will bind to solid organic particles in water, gravity
separation to remove these from wastewater, followed by ozone treatment, can
neutralize the water to a safe level.
Marciniuk is investigating the possibility of developing vaccines for
protein aggregate diseases and others that may be similar, including
Alzheimer’s, Huntington’s, and Parkinson’s diseases. There are some challenges involved
but they are hoping to use the misfolded protein as an antigen. Hou’s research that
our immune system uses infectious aggregates very similar to prion-caused
aggregates suggest that this kind of infectious protein may be more common in
the natural world than we realize.
I would like to raise deer on my farm, that is why I
wanted to research this disease, and there are some risks. Unknowingly buying
infected breeding stock has the potential to transmit prions via ectoparasites
to other animals on my farm or to nearby farms. If contaminated, the pastures
would be unusable for any animals raised for consumption (by humans or other
animals) for an unknown length of time. Another would be the possible contamination
of slaughterhouse facilities and its wastewater, and inability to safely decontaminate
them. And, disposal of bodies after death and loss of investment money.
