South West Water is urging Devon residents to boil their tap water after confirmed cases of cryptosporidium and an investigation is underway

Cryptosporidium, also known as Crypto, are small parasites that live in water and enter the body through food or drink.

They cause a disease called cryptosporidiosis, with the most common symptom being watery diarrhea. It can also cause nausea, vomiting and fever.

Symptoms usually last about two weeks, but can last longer. Young children and people with weak immune systems are at greater risk of being more seriously affected.

The parasites are protected by a thick outer shell that allows them to survive outside the body. They can live for several months in cool, moist conditions.

They are also resistant to chlorine so can live in swimming pools for up to a week.

Ingesting just 10 Cryptosporidium parasites is enough to make you sick

Outbreaks of cryptosporidiosis have been linked to drinking or swimming in contaminated water. Food prepared with contaminated water, such as salads washed with it, can also pose a hazard.

Farmers who handle livestock may also be at risk, as the infection can be contracted from cows, goats and sheep, especially lambs.

Once swallowed, the Cryptosporidium shells break open and release the parasites.

However, some parasites will pass through a person’s digestive system intact, so infection can occur by ingesting fecal particles from an infected person, for example by changing a sick baby’s diapers.

Infected people can shed up to 100 million parasites in one bowel movement. Swallowing just ten is enough to make you sick.

The UK Health Security Agency (UKHSA) provides advice on controlling cryptosporidiosis outbreaks and monitors outbreaks to find the source.