This if referred to as the shotgun treatment. Cooling then down is supposed to be a last resort for causing shock to bacteria and parasites, etc. The problem is that there are no guarantees that it will work. Those temps will cause a lot of stress for the frog and stress weakens their immune system allowing themselves to be open to secondary invaders. Not all strains of bacteria are effected by this range of temperature and Chytrid Fungus will actually thrive in the low to mid 70°s. The Pacman could develope water edema syndrome from prolonged exposure to cool temps causing damage to the Lymph hearts and shortened lifespan. They usually die from this disease. Renal failure can also occur.

Why don't they just medicate them instead of exposeing them to low temps and hoping that they pull through? Or is this method just used to reveal those that are already ill? If that is the case they could figure that out easy with testing rather than waiting for an illness to appear.