Hello and welcome to Prions. After hearing
this lecture, not only will you not want to
eat meat any longer, but more importantly
you should know the history of prion discovery.
You should understand what prions are and
what diseases they cause. You'll know that
there are three different types of prion diseases
and you'll begin to understand the threat
of mad cow disease and chronic wasting disease
to the food supply.
The diseases caused by prions are called transmissible
spongiform encephalopathies. Let's take that
word apart, because it's quite long. An encephalopathy
is a disease of the brain, and as you'll see
in a moment, spongiform reflects the kind
of changes caused in the brain and transmissible
means that they can be infectious. So transmissible
spongiform encephalopathies or TSEs; these
are fatal neurodegenerative disorders of animals.
They're uniformly fatal and they cause changes
to your neurological system. Thousands of
human are diagnosed with TSCs each year and
about 1% of them arise by infection. We will
talk about how the others are acquired as
well. And as an example of a TSC, by 2002, 120
humans had contracted Creutzfeldt-Jacob disease
from eating contaminated meat from animals
with BSE, which stands for bovine spongiform
encephalopathy. The TSC diseases affect many
different animal species, we recognize TSEs
of animals, so for example, bovine spongiform
encephalopathy or BSC, mad cow disease, affects
cows. Chronic wasting disease or CWD is a
prion disease of deer, elk and moose.
Exotic ungulate encephalopathy affects wild game
like nyala and greater kudu, and there are
also diseases of cats, feline spongiform encephalopathy.
We also recognize human TSC diseases, for
example Creutzfeldt-Jacob disease, fatal familial
insomnia, Gerstmann-Straussler syndrome, Kuru
and Variant CJD, all of these animal and human
TSEs are caused by prions.
Why are these so serious? Why do we give an
entire lecture to prion diseases? Well they
are uniformly undetectable before symptoms
develop, we have no diagnostic tests yet that
can tell if you are infected with a prion.
They can't be treated, so once you have symptoms,
you are going to die, because we can't make
you feel better and we can’t prevent your
death and they're invariably fatal. They involve
an incubation period and symptoms which involve
neurological problems, and they all lead to
death. So they're rare, but they are very
Part of the name TSE contains spongiform,
so let's explore that. Spongiform comes from
the fact that the infected brain has holes
throughout it. This is a section of brain
from a sheep with a TSE with a prion disease
and you can see little holes in the brain
and that's why it's called spongiform. All
of these diseases are associated in human
with severe psychomotor dysfunction, and the
exact symptom depends on which part of the
brain is damaged, it can be different for
the different prion diseases. Each disease in fact,
Creutzfeldt-Jacob, Gerstmann Straussler, etc.
has a distinct symptom pattern and pathology
associated with it, but of course they all
involve the brain and spinal cord.