Nineteenth century medicine was an interesting topic to research in preparation for writing The Haweaters. Doctors were in short supply on Manitoulin Island in 1877, the year The Haweaters is set, and I could find reference to just one who was in permanent residence on the island. So if a settler found themselves needing medical care, they or someone close to them could have to travel significant distances, often by foot, to track down that sole doctor or wait considerable time for him to make his way to them.
Dr. William Stoten Francis -- the real-life Manitoulin doctor who performed the autopsies on William and Charles Bryan -- was contracted to act as a physician to the indigenous communities on the island, but would also tend to the needs of those early European settlers who would most likely have restricted their dealings with him to life and death situations, seeing wisdom in tackling minor ailments and/or injuries on their own. And that could be tricky in the decades before antibiotics were invented.
One day when sifting through historical documents, I found a recipe for a poultice that would have been used by those early Manitoulin residents. These sorts of homespun remedies were commonly used to cure absolutely everything that was considered to be curable back then. And I do mean everything. Poultices were used to soothe inflammation, subdue infections, and speed the rate at which insect bites, abscesses, cysts, splinters, boils, and styes healed. They were applied to toothaches and animal bites as well as being used to remove corns and knock out colds. They were also considered invaluable in conquering just about any ailment that impacted the lungs including congestion, bronchitis, pneumonia and tuberculosis. Poultices were even used in the treatment of cholera.
If you want to try treating your cholera (or any other ailment) with a poultice, here's a recipe for a bread poultice that was actually used on the island:
1/4 c. sweet milk
1/2 tsp. sugar
1" square of bread
Boil the milk then stir in the sugar. Add the bread and allow it to soak up the milk then ring out the moisture. Apply the wet bread to a gauze and press it to the affected area. I couldn't even begin to tell you how long you need to keep the poultice in place. Presumably until whatever it is you're trying to cure takes a turn for the better, if it takes a turn for the better.