Following recent headlines about Cryptosporidium outbreaks in Devon water and in food sources nationwide, PWTAG has updated swimming pool operators on what they need to know. Technical Note 30 provides key information on cryptosporidiosis (the disease it causes) and measures for their control.
Cryptosporidium is a protozoan parasite that multiplies in the gut of humans and other animals. The life cycle stage that is shed in faeces is called an oocyst. People become infected when they swallow oocysts; just one is enough to make someone ill with cryptosporidiosis. Anyone can get cryptosporidiosis, but it is especially common in young children. The main symptoms are watery diarrhoea, abdominal pain, nausea and/or vomiting and low-grade fever.
People might swallow oocysts when they have close contact with an infected person or animal and their faeces, or through eating contaminated food, or swallowing contaminated water. Most people become ill five to seven days after ingesting oocysts. Symptoms usually last up to two weeks, but sometimes longer – and may come and go before full recovery.
Some people with very weakened immune systems have serious, possibly life-threatening illness. Cryptosporidiosis outbreaks can happen in many settings, such as open farms where people have contact with animals, or nurseries where children are in close contact with each other, or in communities where drinking water has become contaminated.
But swimming pools are the most common setting for outbreaks of cryptosporidiosis. Filtration – low or medium-rate and with coagulation – is the key to removing oocysts. But not all oocysts will be removed in a single pass of pool water through the filters, however good the pool’s water circulation.
The pool will have to be closed if contamination is suspected so that the water can be circulated through the filters sufficiently to remove the contamination. Secondary disinfection (UV or ozone) also helps, and super chlorination can also be considered. Make sure your pool tells users not to use the pool when they have diarrhoea, or for 48 hours after symptoms stop.
If they have had cryptosporidiosis, they must extend that to a fortnight after symptoms stop. If an outbreak of cryptosporidiosis has been identified, it may be that some regular bathers will have had diarrhoea, but not had the illness diagnosed. They too should be excluded from using the pool for a fortnight after symptoms have stopped.
Pool Water Treatment Advisory Group
chair@pwtag.org
www.pwtag.org
