Transcript PowerPoint Presentation - Society`s Creation of Disease

Human Behavior and
the Rise of Disease
Plan for Today
Last week: How disease shapes society
Today: How society shapes disease
– Antibiotic resistance
– Mad Cow disease
Topic 1: Antibiotic Resistance
First, some questions for you
1. How many of you have ever taken an antibiotic
at a time when you were not prescribed to do so
by a doctor?
2. How many of you use antibacterial soap?
3. How many of you think it is possible for a
disease to become resistant to antibiotics?
4. How many of you think it is possible for a
human being to become resistant to antibiotics?
How does antibiotic resistance work?
• Resistance to a particular antibiotic can arise as a mutation in
bacteria
– For example, Streptomycin resistance occurs in about 1 out of
every 2,500,000,000 e. coli bacteria.
• Ordinarily these get cleaned up by the immune system.
• If the immune system doesn’t get all of them, you can have
problems.
– First, bacteria will repopulate after most have been killed by
an antibiotic
– Next, the survivors will include a disproportionate number of
antibiotic-resistant bacteria
– Finally, these antibiotic-resistant bacteria reproduce, so the
antibiotic-resistant genes will be at a much higher frequency
in the next generation
– Ultimately, antibiotics will be far less effective in fighting off
this bacterial infection if it spreads to others
And…it gets worse
1. You have tons of good bacteria in your body
–
–
For example, e. coli in your digestive tract produces vitamin K,
which helps with blood clotting
every time you take antibiotics, you kill the good and bad
bacteria
2. Over time, you can build up crops of antibiotic-resistant
bacteria in your body
–
if you’ve got antibiotic-resistant bacteria, then pathogens
entering your body could pick up the resistance from the bacteria
through the exchange of plasmid (small pieces of DNA)
Every time you use antibiotics, you increase the chances that
your body will contain antibiotic-resistant strains of
bacteria
Some of the Results of
Antibiotic Resistant Bacteria
• Almost no one takes penicillin anymore because
too many bacteria are resistant to it
– This is happening with many common antibiotics
• New antibiotics need to be phased in constantly
– Anyone heard of Cipro before the anthrax scare?
– Pharmaceutical companies keep some drugs in reserve
for future use, when other antibiotics become useless
Some Handy Hints for You
1. Do use antibiotics when they are prescribed by a
doctor
2. Do not use an old antibiotic prescription when you
are feeling sick–see a doctor
3. Do avoid antibacterial soap (if possible). All soap
kills bacteria by breaking down the cell membrane.
4. If you are a farmer, do not spray your crops with
antibiotics (they do this to prevent rot due to bacteria)
And an assignment for next time
Please find 5 people you know and ask them the following
questions. They should not be students in the class (though
fellow Westminster students are acceptable). Record their
answers and we will discuss as a group in class next time:
1)
2)
How affective are antibiotics at fighting colds?
Have you ever taken an antibiotic at a time when you were not
prescribed to do so by a doctor?
3)
Do you use antibacterial soap?
4)
Is it possible for a disease to become resistant to antibiotics?
5)
Is it possible for a human being to become resistant to
antibiotics?
6)
Did you know that many farmers (particularly fruit growers)
treat their crops with antibiotics? Do you know why they do that?
Topic 2: Mad Cow Disease
A.K.A. Bovine Spongiform
Encephalopathy (BSE)
First, a question
How many of you eat beef?
Some Background
How do you prove that a particular agent causes a
particular disease?
1. Prove the agent is present in every instance of
the disease
2. Isolate the agent from a diseased individual and
grow it independently
3. Use that sample to cause the disease in a healthy
individual
4. Recover the agent from that infected individual
Is it this easy?
• This process is easy with bacteria since they’re
relatively big (so we can see them) and they
reproduce fast
• It took scientists longer to find viruses because
they’re tiny
• With Mad Cow Disease, the problem is that the
agent that has been identified (a protein called a
prion) does not appear to reproduce itself, so
scientists cannot fully test if it is responsible for
the disease
So there are three options:
1. Keep looking for a different cause for the disease
2. Claim that the cause of the disease is really weird
3. Find circumstantial evidence
Scientists have gone with option #2 and 3
2: they believe the prion infects normal healthy proteins
through an unknown process
3: all the ways that we kill normal pathogens (cooking,
poisoning, radiation, etc) don’t work with this disease,
so it can’t be a bacterium or virus
1.
How
does
the
infection
work?
A person ingests an abnormally-shaped prion from contaminated food.
2. The abnormally-shaped prion gets absorbed into the bloodstream and
crosses into the nervous system.
3. The abnormal prion touches a normal prion and changes the normal
prion's shape into an abnormal one, thereby destroying the normal prion's
original function.
4. Both abnormal prions then contact and change the shapes of other normal
prions in the nerve cell.
5. The nerve cell tries to get rid of the abnormal prions by clumping them
together in small sacs
6. Because the nerve cells cannot digest the abnormal prions, they
accumulate
7. The sacs of prions grow and engorge the nerve cell, which eventually
dies.
8. When the cell dies, the abnormal prions are released to infect other cells.
9. Large, sponge-like holes are left where many cells die.
10. Numerous nerve cell deaths lead to loss of brain function, and the person
Where did it come from?
• To get BSE, you need brain contact with an
infected organism
• How does this happen? Through eating
brain, of course, either as a delicacy or in
ground beef!
It’s all about the cows
• Normally, cows are herbivores
• To make beefier cows, big farms often give
cattle beef to eat–if the feed beef is
contaminated with brain, BSE can be passed
to many cows
An Irony
• So the cattle industry, in order to make money, fed cows
beef that was unknowingly contaminated with cow brain
• As a result, in Britain, millions of cows had to be destroyed
and people are still afraid to eat British beef (this could
happen in the U.S. also, although there is at this point no
evidence for BSE in any U.S. cows)
P.S. Safety checks are now in place in the U.S.
– most meat by-products are prohibited in animal feed
– no feed or animals are imported from countries with BSE
outbreaks
– oddly behaving cows are tested for BSE
Can humans get Mad Cow Disease?
• Maybe–was a rise of BSE in cows and CreutzfeldtJakob Disease in humans in Britain but no definite link
found
• C-J Disease symptoms:
– Early: failing memory, lack of coordination, visual
disturbances
– Middle: pronounced mental deterioration, blindness, coma
– End: death (usually within 1 year of onset of symptoms)
In sum…
• Human behavior can significantly impact
the rise and development of disease
• Another big theme as of late: don’t mess
with Mother Nature
– More on this next time, when we’ll do some
background on genetically modified foods