Cholera is a disease caused by the bacteria Vibrio cholerae. This bacteria secretes a toxin that binds to the cells of a small intestine. The small intestine is then unable to perform its normal functions such as regulating the amount of fluid absorbed by cells and thus, a large amount of fluid enters the small intestine and is excreted in the feces. This creates diarrhea, which can be helpful when flushing out unwanted pathogens, but if the diarrhea is severe and long lasting, as it occurs in cholera, too much fluid is lost and the body becomes dehydrated. Along with dehydration, the cholera toxin binding to the small intestine may also result in loss of electrolytes. Electrolytes are chemicals vital to the bodies control of blood pressure, excretion of metabolic wastes, and maintenance of blood sugar levels. The cholera toxin causes the small intestine cells to excrete large amounts of electrolytes which are then excreted in diarrhea.
The toxin is made up of two subunits: subunit A and subunit B. Subunit A is the poisonous part of the toxin, and subunit B is nontoxic. The subunit B attaches to a cell in the small intestine and makes a channel within the cell membrane, and subunit A enters through this channel. Subunit A disrupts the production of the correct amount of fluid and electrolytes, thus the fluid and electrolytes leave the cell and enter the small intestine.