Pennsylvania Game News - June 2019 - 7

and viruses, this led Prusiner to search
for alternative sources of scrapie.
Prusiner then found that if he removed
all proteins from sample material, animals were unable to become infected
from the sample material suggesting
scrapie must be caused by a protein.
Prions are misfolded or distorted versions of proteins. In their normal shape,
the proteins are not harmful to the body
and most likely help with cellular function. When misfolded, however, they
cause disease that results in the formation of tiny holes in the brain.
Since Prusiner's initial findings, a
wealth of research has been published to
support the idea prions cause TSE diseases, and all TSE diseases are believed
to be caused by prions.
When a pathogen, such as a bacteria
or virus, enters the body, an immune
response is triggered because the pathogen is not recognized as part of the body,
but as an invader. To fight these invaders, the immune system quickly induces
fever and inflammation, which is the
body's way of inactivating pathogens.
If the body has been infected with
a pathogen previously, the immune
system is able to recognize the pathogen
and produces antibodies, which attach
to and neutralize the pathogen.
TSE infections have not been found
to induce fever, inflammation or antibodies, suggesting the immune system
either recognizes the infectious agent as
being part of the body or does not notice
the infectious agent at all.
Since prions are commonly found
in mammals, it makes sense that the
immune system does not recognize
prions as invaders.
All of these findings and more sugJUNE 2019

gest that TSE diseases are not caused
by a bacteria or virus.
Whether CWD is caused by a prion
or bacteria doesn't change the Game
Commission's need to manage the disease and try to limit its spread to new
areas. But the distinction does matter
in relation to CWD vaccines and field
tests that are said to be nearing completion. Those vaccines and field tests are
built on the idea that CWD is caused
by bacteria.

MEHDISisSa bigger threat than CWD to
our deer herd.

It is true that Epizootic Hemorrhagic
Disease (EHD) can have significant
impacts on deer populations locally
where the disease hits. But CWD has the
potential to reach farther and become a
more-permanent problem.
EHD is a virus that is spread by tiny
biting midges, or "no-see-ums." Pennsylvania has been impacted only about
once every five years, with outbreaks
occurring over small areas during the
summer. The midges then die off after
the first hard frost.
Even though EHD quickly can kill
large numbers of deer, it is not always
fatal.
Many deer that contract EHD survive
and develop resistance to the disease.
Even in those areas where EHD causes
large deer die-offs, those local populations can rebound quickly.
One of the most dangerous things
about CWD is that its effects are not
easily visible.
Instead, CWD picks at a population,
one deer at a time. Then, over time, the
disease takes an increasing number of
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Pennsylvania Game News - June 2019

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