Basically, vibrio cholerae is bacteria that is taken in by humans when we eat or drink contaminated things. It produces a toxin which is a protein, and this binds to the protein channels of the epithelial cells in the small intestine. This causes some of the protein channels to stay open. Chloride ions then move from the epithelial cells (where there is a higher concentration) and into the lumen of the small intestine (where there is a lower concentration) by diffusion. This then means that the water potential of the epithelial cells is higher than that of the lumen of the the small intestines, so water moves from these cells and into the lumen of the small intestine by osmosis. This causes lots of water to be lost, so dehyration can occur.

it gets into the intestine and causes the Cl channels to open up in the epithelium cell and causes profuse watery diarrhea,
vomiting, and
leg cramps.