What is causing the rash is unknown at this time. People have suggested possible causes. Protozoa is just " one " of the posibilities. You can't determine the solution for this problem, until you know what specific agent is causing the rash, and, what causes the agent to be in the hotpools. What if this problem is found to derive from the human activity around the springs. Maybe then we should ban the humans, and the dogs will have that little paradise all to themselves :-)