Crypto: what you need to know about the water parasite making people ill in Devon

For the past two weeks, people in the south Devon town of Brixham have started contracting the disease known as crypto. There are now about 16,000 homes and businesses at risk of crypto infection due to contaminated drinking water. But what is actually going on?

What is cryptosporidium?

Cryptosporidium (crypto for short) is a single-celled microorganism that causes the intestinal disease cryptosporidiosis.

Crypto is a parasite. Biologically, it is more closely related to humans and other animals than to most other disease-causing microorganisms, such as viruses and bacteria. This is important as the way we diagnose and treat parasites can be very different to how we handle bacteria and viruses.

Crypto is a waterborne parasite that infects both humans and animals. It can be found in rivers, lakes, swimming pools and reservoirs contaminated with faeces. Due to its ability to survive outside a human or animal host in the form of an oocyst (a thick-walled structure containing immature, dormant parasite spores), viable crypto can be present for several weeks or even months before infecting another individual.

What happens when people are infected with it?

When crypto oocysts are swallowed, usually by drinking contaminated water or with direct contact with infected people or animals, cells pass through the stomach into the small intestine. There they become active and begin multiplying.

After several days this results in inflammation of the bowl with the common symptoms being watery diarrhoea, vomiting, stomach pains and potentially a fever. In persistent infections, this can lead to dehydration and even weight loss, although this is rare.

Infected people are contagious as crypto oocysts will be shed in their faeces. Good hygiene must be maintained in an infected household to limit its spread.

Are any groups particularly vulnerable to a crypto infection?

Many people who become infected with crypto will not develop any symptoms at all. However, young children (one to five years of age) and people with weakened immune systems are more susceptible.

People caring for infected individuals are also at risk as infection can be spread through direct contact. Avoiding direct contact with the mouth and regular handwashing will help avoid infection and limit the spread. If you suspect you are infected with crypto contact your GP.

How is it treated?

Unfortunately, there is no direct treatment for cryptosporidiosis. In extreme cases, certain drugs, such as paromomycin (an antibiotic), might be prescribed by your GP, but this usually only reduces the symptoms. It does not cure crypto infection.

Rehydration and replacement of electrolytes are the most important treatment as diarrhoea and vomiting will cause significant water loss. Of course, drinking while vomiting can be difficult, so drink little and often.

Cryptosporidiosis will clear up on its own, usually in two to four weeks. People with compromised immune systems may take longer to recover.

It is often reported that people appear to recover only for the symptoms to return. If this happens to you, don’t worry, just carry on rehydrating and contact your GP.

How does crypto get into the water supply?

Crypto is spread from the faeces of infected people and animals, such as cows, pigs and sheep. The most likely source of contamination for the current Brixham outbreak is farm animal waste entering the local water supply at Hillhead reservoir.

The parasite is resistant to chlorine and so can survive in tap water where many other parasites and bacteria cannot. For this reason, it is important to boil tap water before drinking to kill oocysts of the parasite, stopping the infection. Alternatively, drinking bottled water will eliminate the source of infection.

How long is this outbreak likely to last?

Once the source of contamination has been stopped it could be several weeks or even months before crypto is no longer detected in drinking water.

People infected will probably take several weeks to fully recover but remain contagious. Limited contact between those infected and uninfected will help reduce the time of the outbreak. As a result, the outbreak will probably last several weeks or even months depending on how quickly the source of contamination is removed.

How often does this kind of thing happen in the UK?

Outbreaks of crypto in the UK are rare. There are between 3,000 and 6,000 confirmed cases every year in the UK, often caused by the parasite spreading between young children in nurseries. This number is probably higher if cases are not reported correctly or are assumed to be just another tummy bug.

In 2016, there was a major crypto outbreak in Wiltshire, affecting hundreds of people. This was linked to a contaminated swimming pool where water would have been accidentally swallowed. This kind of situation is uncommon so there is no need to avoid bathing unless there is a known outbreak.

However, several recent studies have found rates of crypto infection are increasing across Europe. With this in mind, outbreaks in the UK might unfortunately grow.

Lee Hutt does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.