Chapter 4: An Arms Race Without Ends

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Chapter 4 An Arms Race Without Ends
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Red Queen Principle

• it takes all the running you can do, just to
  keep in the same place.
• -The Red Queen
• (from Alice in Wonderland)
• Example Fox and rabbits

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Trial and Error

• Evolution is trial and error there is no
  rational planning or fresh starts.

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Host vs. Pathogen Advantage

• Host Advantage
• People who have had a disease are less likely to
  be re-infected because their body is prepared for
  that particular pathogen
• Pathogens Advantage
• Small size
• Large numbers
• Evolves quickly

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Resistance to Penicillin

• 1941 all are vulnerable
• 1944 some have evolved
• 1950s methicillin is introduced
• Bacteria evolves to be unaffected
• Today 95 show some resistance

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Bacterial Resistance to Antibiotics

• Tuberculosis
• Once controlled by antibiotics, now kills 50 of
  its hosts

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Prolonged Exposure

• Prolonged exposure to antibiotics can build up
  resistances
• Example Antibiotics in eggs and milk

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Virulence

• Virulence
• The ability of the pathogen to use the hosts
  resources for itself
• PERSONAL CONTACT LESS VIRULENT
• INSECT MORE VIRULENT

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Cultural Vectors

• Ways of transmitting disease in everyday life
• Unsanitary water
• In hospitals
• Unwashed hands
• Thermometers
• Eating utensils

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Immune System Response

• The immune system makes two kinds of mistakes
• Attacks when it should not
• Fails to attack when it should

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Mimicry

• When one organism copies another so it can
  benefit from what is has gained
• Example Monarch and viceroy butterflies
• Pathogens use mimicry to
• Escape attack
• Attack without being detected

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Novel Environment Factors

• Epidemics are caused by
• Changed social conditions ( travel )
• Modern technology ( Legionnaires Disease )
• Overpopulated spaces ( TB)
• Best intentions ( improved sanitation )

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Summary

• The body is constantly at war with pathogens
  because each time a battle is won, there is
  another battle waiting to be fought.

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