Cholera (Cambridge (CIE) IGCSE Biology): Revision Note

Cholera

Cholera causes diarrhoea

• Diarrhoea is the loss of watery faeces from the anus

• If it is severe and continues for a long time, it can lead to death

• Severe diarrhoea can cause the loss of significant amounts of water and ions from the body, causing the tissues and organs to stop working properly

• It can be effectively treated by oral rehydration therapy

• This is a drink with a small amount of salt and sugar dissolved in it

• There are many causes of diarrhoea, one of which is infection with Vibrio cholerae bacteria, which causes the disease cholera

How does Vibrio cholerae cause diarrhoea?

• Ingested via infected water or food, if it enters the small intestine it can cause illness in the following way:

1. Bacteria attach to the wall of the small intestine

2. They produce a toxin

3. The toxin stimulates the cells lining the intestine to release chloride ions from inside the cells into the lumen of the intestine

4. The chloride ions accumulate in the lumen of the small intestine and lower the water potential there

5. Once the water potential is lower than that of the cells lining the intestine, water starts to move out of the cells into the intestine (by osmosis (opens in a new tab))

6. Large quantities of water are lost from the body in watery faeces

7. The blood contains too little chloride ions and water