Cryptosporidium

Symptoms: Within 1 2 weeks of ingesting the parasite, the following symptoms may be experienced diarrhoea, bloating, cramping and abdominal pain. There may be vomiting but this is uncommon.
The illness can last up to 3 weeks.

Where does it come from and how does it spread?

This illness is caused by a microscopic parasite which enters the body in contaminated food or water, by person to person spread or contact with farm animals and pets.
If water is the suspected source of your illness then bringing water to the boil will kill the parasite, the cooled water can then be used for drinking and food preparation.