How the cholera bacterium causes disease
Symptoms:
Diarrhoea
Dehydration
(Some people show few, if any, symptoms- only acting as carriers (spreading the disease unwittingly)
Transmission:
By the ingestion of water (or more rarely food) that has been contaminated with faecal material containing this pathogen.
Once ingested symptoms are caused by the following ways...

Almost all Vibrio cholerae bacteria ingested by humans killed by acidic conditions in stomach. However, few may survive (especially if pH is about 4.5)
When surviving bacteria reach small intestine they use flagella to propel themselves through mucus lining of intestinal wall.
Produce a toxic protein which has 2 parts. One part binds to specific carbohydrate receptor on CSM (the epithelial cells of the small intestine are the only ones to have these specific receptors- explaining why cholera only affects this region of the body.) 2nd part enters epithelial cells causing ion channels of CSM to open so chloride ions (normally contained within cells) flood into lumen of intestine.
Loss of chloride ions in cells raises water potential, while increase of ions in lumen lowers water potential. Water therefore flows from cells into lumen.
Loss of ions from cells establishes conc. gradient. Ions therefore move by diffusion into cells from surrounding tissues, including blood. This, in turn, establishes water potential gradient causing water to move by osmosis from blood/other tissues into intestine.
It is the loss of water from blood/other tissues which cause symptoms of cholera.

	Created by hannah.lindridge over 11 years ago

A-Levels Biology (Cells & movement in/out of them) Note on Cholera, created by hannah.lindridge on 15/05/2013.