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  • Cholera
    • Pathogens cause disease by producing toxins and damaging cells
      • Production of toxins
        • Many bacteria release toxins into the body. The bacterium that causes cholera produces a toxin that upsets the exchange of substances in and out of cells
      • Cell damage
        • Pathogens can physically damage host cells
          • Rupturing them to release nutrients inside them
          • Breaking down nutrients inside the cell for their own use. This starves and eventually kills the cell
          • Replicating inside the cells and bursting them when they're released
    • Cholera Bacteria produce a Toxin that affects Chloride Ion Exchange
      • The toxin causes chloride ion protein channels in the plasma membranes of the small intestine epithelial cells to open
        • Chloride ions move into the small intestine lumen. The build up of chloride ions lowers the water potential of the lumen
          • Water moves out of the blood, across the epithelial cells and into the small intestine lumen by osmosis
            • The massive increase in water secretion into the intestine lumen leads to really, really, really, bad diarrhoea - causing the body to become extremely dehydated
    • Oral re-hydration solutions are used to trat diarrhoeal diseases
      • An oral rehydration is a drink that contains large amounts of salts (sodium ions, chloride ions) and sugars (glucose, fructose) dissolved in water
        • Sodium ions are included to increase glucose absorption
          • Getting the concentration of the ORS right is essential for effective treatment
            • An ORS is very cheap treatment and the people administering it dont require much training. This makes it great for treating diarrhoeal diseases in developing countries
    • New Oral Re-hydration Solutions can be Tested on Humans
      • Diarrhoeal diseases mostly affect children, so many trials involve children. Parents decide whether the child will participate in the trial. The child doesnt make their own decision - some people think this is unethical
        • But scientists believe the treatment must be trialled on children if its to be shown to be effective against a disease that mainly affects children
      • Clinical trials usually involve blind trial. This is where some patients who are admitted into hospital with diarrhoeal diseases are given the standard ORS and others are given the new ORS, This means that the two can be compared. Some people dont agree with this - they think that people have the right to know and decide on the treatment that theyre going to have
        • Scientists argue that a blind trial is important to eliminate any bias that may skew the data as a result of patients knowing which treatment they've recieved
      • When a new ORS is first trialled theres no way of knowing whether itll be better than the current ORS there is a risk of the patient dying when the original better treatment was available


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