The challenge of Cryptosporidium and swimming pools

Cryptosporidium management in swimming pools

Prof. Rachel ChalmersDirector, Cryptosporidium Reference Unit

Public Health Wales MicrobiologySingleton Hospital

Swansea

The problems

• The parasite

• The pool

• The people

Why is Cryptosporidium important in swimming pools?

• no disinfectant residual in the pool that kills Cryptosporidium

• Effective disinfectants (UV, ozone) are progressive, in the treatment plant room, add-ons

• Rely on removal: only good circulation, optimal filtration with coaggulation (flocculation) will remove oocysts….progressively (contrasts to drinking water)

How does Cryptosporidium get into pools?

• Bad plumbing

• Poop in the pool

• Unrecognised incidents and dirty bathers

• Subsequent propagation through poor design, construction and management at the pool – need to be able to identify this

The people • Pool users

Children <5 years have highest incidence of cryptosporidiosis Those most likely to shed oocysts, have a faecal accident….and get

cryptosporidiosis

• Oocyst shedding 106 to 107 opg during acute infection Shed for 2 weeks after symptoms cease A study in Wales showed 8% (upper 95% CI 15%) cases used

swimming pools while infected (Sarah Jones, pers. comm) Carriage in 1.3% (upper 95% CI 4%) nursery children (Davies et al.

2009)

• Pool water consumption estimate children 6-18 years average consumption is 37ml (Dufour et al.

2006)

Child with cryptosporidiosis poops in the pool

50 million oocysts per ml of poop X 150 mls poop = 7500 million oocysts into the pool.

In a typical 25x12m pool (450m3) that would be an average concentration of 20 000 oocysts per litre or

20 oocysts per ml.

Estimate children 6-18 years average consumption is 37ml or

740 oocysts.

Risk

• If Cryptosporidium contaminates a swimming pool, bathers are at risk of infection.

• The size of that risk depends on: bather behaviour

immediate actions taken following incidents such as faecal accidents.

the design and construction of the pool

effectiveness of the treatment and secondary disinfection

management and operation of the pool

• Implement a clear policy for recognising, reporting and dealing with faecal accidents

• Parents must be encouraged to adopt practices which will limit the chances of faecal contamination

• People with diarrhoea must not swim in swimming pools or for 48 h after

• 2 week exclusion for cryptosporidiosis cases

• Strategies to educate users

Keeping Cryptosporidium out of the pool

All-Wales LIMS SOP: laboratory reporting includes

advice for patients

Where Cryptosporidium oocysts are seen in primary diagnosis, an automated comment will be added:

“In addition to the usual advice to prevent person to person spread, all patients diagnosed with cryptosporidiosis must not use swimming pools until 2 weeks after the diarrhoea has stopped”.

Examples of contributory factors in outbreaks of cryptosporidiosis 1

Factor Example from outbreaks

Sewage cross-connection. Contamination in plant room.

Inadequate pool design and construction, including water features.

Absence of as-built schematics; filter by passing; lack of flow meters or pressure gauges.

Faecal release or contamination from bathers.

Documented releases; faeces smeared on water features; people continuing to swim with diarrhoea or after diagnosis; lack of adequate hygiene; bather loads exceeded.

Inappropriate handling and disposal of stools.

Disposed of in scum channel.

Inappropriate response to faecal accidents.

Not documenting; not following PWTAG procedure.

Secondary treatment absent or not working properly.

UV lamps failed; ozone decommissioned.

Examples of contributory factors in outbreaks of cryptosporidiosis 2

Factor Example from outbreaks

Inadequate pool water circulation.

Deadlegs; inadequate pumps.

Inadequate coagulation. Coagulation absent or slug dosed.

Inadequate filtration. Inappropriate filter media; laterals installed incorrectly; filters poorly installed and maintained.

Filter backwashing problems. Not observed.

Inappropriate backwashing procedures.

Timing; frequency.

Gaps and weaknesses in policies and operational procedures and non-adherence to procedures.

Contribute to spreading Cryptosporidium contamination widely in the pool.

Confusion in determining which national standards to apply

Warm, large hydrotherapy-style pools.

Some key lessons from outbreaks• Good design and construction will prevent cross connections and spread of contamination (as-built schematic).

• Adequate pool water circulation, coagulation and filtration help to remove contamination (as-built schematic).

• Any pool could be mismanaged in a way that will cause an outbreak but a rapid and appropriate response can reduce risk.

• Entire pool industry engagement for risk assessment and solutions.

• Training and education e.g. PWTAG CoP.

• Public engagement to encourage healthy swimming; there is evidence that promotional efforts can reduce outbreaks.

• Co-ordinated response plan: guidance for investigation is available, with an inspection checklist.

Guidance for the investigation of

Cryptosporidium linked to swimming pools www.publichealthwales.org/cryptopoolguidance/

Task and finish group:• Public Health Wales and Public Health England• Local Authorities• Chartered Institute of Environmental Health• Pool Water Treatment Advisory Group • Chartered Institute for the Management of Sport and Physical

Activity

Aim to assist public health professionals in their investigations by outlining the:

• regulatory framework

• normal pool operating parameters and standards

• emergency actions

• sources of independent advice

• methods for establishing and investigating links between cases of illness and pools

• key points in inspecting swimming pools CHECK LIST

• key public health messages.

Prevention

• Pools that are properly constructed with good filtration

• Pools for young children on separate filtration systems

• Prevent pollution from outside; maintain cleanliness of pool surrounds

• Encourage toileting, hand hygiene and effective showering/rear end cleaning prior to swim

• Discourage swallowing pool water

• Swim nappies, not normal nappies. N.B. Swim nappies do not confine diarrhoea: they leak!

• Properly equipped, convenient nappy changing and disposal facilities

• Encouraging and enforcing exclusions

Wider implications of the guidance

• Aimed at public health professionals in England and Wales:

Local Authority Environmental Health investigating officers

Health Protection Units/Teams

• Implied implication for how pool operators prevent, prepare for and deal with incidents throughout the UK.

Alarm bells

• Ask for a schematic diagram of the pool water treatment – if they can’t produce one off the shelf, what else don’t they know about their pool?

• General management and practices (faecal accident policies, filter backwashing etc)

Waterborne Crypto: your key resources• DWI• Bouchier report on DWI website: www.dwi.gov.uk

• PHW/PHE guidance.

• PWTAG’s 2009 Swimming Pool Water treatment and quality standards for pools and spasISBN 0951700766.

• Me.

www.publichealthwales.org/cryptopoolguidance/

Rachel ChalmersUK Cryptosporidium Reference Unit

Public Health WalesMicrobiology ABMSingleton Hospital

Swansea

01792 285341