Managing Cryptosporidium in Public Swimming Pools

Cryptosporidium Risk Management

The risk of a pool contaminated with Cryptosporidium is directly related to the organism’s characteristics and the transmission/epidemiology of the disease. Briefly, infective Ocysts are resistant to standard levels of chemicals (as used in pool disinfection). They are unlikely to be adequately removed by the pool filtration system due to the small size of the Ocysts and the pool’s basic operating method using consecutive dilutions.

The first symptoms of cryptosporidiosis may appear 1 to 12 days after a person ingests the infective Ocysts. Symptoms of the disease usually include profuse watery diarrhoea, abdominal cramps, fever, nausea and vomiting. These symptoms may lead to weight loss and dehydration. Some infected people may not have symptoms, yet excrete Ocysts in their faeces. There is no specific treatment for cryptosporidiosis.

People with healthy immune systems usually have symptoms for one to two weeks and then recover fully. After symptoms subside, they may still continue to pass Cryptosporidium Ocysts in their faeces for several days and therefore may still spread the disease to others.

Those with a weakened immune system, may have cryptosporidiosis for a longer period of time; in some cases the illness can be serious and even life threatening. People with compromised immune systems should discuss with their doctor the risk of catching cryptosporidiosis, including swimming at public facilities and the need to take precautionary measures. Examples of people with weakened immunity include infants, people with HIV/AIDS, cancer and transplant patients (who may use or rely upon immunosuppressive drugs) and or people with inherited diseases affecting their immune system.

A review of the outbreaks of Cryptosporidiosis associated with swimming pools shows that the majority occur in pools following faecal accidents by infants, who are not toilet trained. The majority of other illnesses transmitted in facilities are directly associated with poor disinfection.

To reduce the risk of Cryptosporidium entering a pool it is required that pool operators prepare SOP’s to prevent the introduction of Cryptosporidium into pools and to implement control measures to inactivate Cryptosporidium. This risk assessment should address the following risk management areas:

  • Swimmer hygiene practices – encourage pre‐swim bathing with soap.

  • Education – let patrons know why and what you are doing, it’s better to be open and frank.

  • Operational control and maintenance – maintain vigilance and be prepared for incidents.

  • Sampling – conduct the required microbiological testing and accept such costs as being a duty of care.

The single most effective method to prevent the transmission of Cryptosporidium in swimming pools is to stop Ocysts from entering the pools in the first instance by improving swimmer hygiene practices. There are two priority areas:

  • Bather personal hygiene

  • Non toilet trained infants

People, particularly children, who have had diarrhoea within the previous two weeks, should not swim. All other patrons should be encouraged to:

  • Use the toilet before entering the pool

  • Shower and wash thoroughly all over with soap before entering the pool

  • Avoid swallowing pool water as it may contain un‐disinfected pathogenic micro‐organisms

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