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Article

Occurrence of Cryptosporidium Oocysts in Leisure Pools in the UK, 2017, and Modelling of Oocyst Contamination Events

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Cryptosporidium Reference Unit, Public Health Wales Microbiology and Health Protection, Singleton Hospital, Swansea SA2 8QA, UK
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Swansea University Medical School, Swansea University, Singleton Park, Swansea SA2 8PP, UK
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Pool Sentry Ltd., Dale Cottage, Stanton Dale, Ashbourne DE6 2BX, UK
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IDEXX Technologies Ltd., Units 1B & 1C, Newmarket Business Park, Studlands Park Avenue, Newmarket, Suffolk CB8 7ER, UK
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Latis Scientific Ltd., Unit C1 Acorn Industrial Park, Crayford, Kent DA 1 4AL, UK
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Public Health England, Seaton House, London Road, Nottingham NG2 4LA, UK
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Author to whom correspondence should be addressed.
Academic Editor: Athena Mavridou
Water 2021, 13(11), 1503; https://doi.org/10.3390/w13111503
Received: 21 April 2021 / Revised: 20 May 2021 / Accepted: 26 May 2021 / Published: 27 May 2021
(This article belongs to the Special Issue Healthy Recreational Waters: Sanitation and Safety Issues)
Cryptosporidium is a major cause of diarrhoea outbreaks linked to swimming pools, but little is known about the frequency of contamination. The primary aim was to investigate the occurrence and concentration, through sampling and modelling, of Cryptosporidium oocysts in leisure pools. Secondary aims were to compare detections with operational parameters, provide the evidence-base for guidance, and improve sampling capacity and interpretation for public health investigations. Up to 1000 L pool water was sampled during swim sessions once weekly for 10 weeks from 8 August 2017 at six volunteer pools. Oocysts were detected by microscopy in 12/59 (20%) pool water samples, at least once in each pool; 8/12 (66%) detections were in August when bather loads were highest. At three pools, 1 L filter backwash was sampled weekly and oocysts were detected in 2/29 (7%) samples, following detections in pool water. The probabilities of a bather contaminating the pool ranged from 1 in 1000 to over 1 in 10,000. Monte Carlo analysis showed that when high bather numbers caused contamination on over 70% of days, multiple events per day were more likely than single events. In these generally well-managed leisure pools, Cryptosporidium risk related to high bather loads. We conclude that public awareness campaigns for bather hygiene, and reminding pool operators of current guidance for managing faecal accidents, should be ahead of peak swim season. View Full-Text
Keywords: backwash; cryptosporidium; occurrence; oocyst counts; swimming pool water; probability modelling backwash; cryptosporidium; occurrence; oocyst counts; swimming pool water; probability modelling
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MDPI and ACS Style

Chalmers, R.M.; Simmonds, L.P.; Wood, M.; Luxford, M.; Miller, R.; Johnston, R. Occurrence of Cryptosporidium Oocysts in Leisure Pools in the UK, 2017, and Modelling of Oocyst Contamination Events. Water 2021, 13, 1503. https://doi.org/10.3390/w13111503

AMA Style

Chalmers RM, Simmonds LP, Wood M, Luxford M, Miller R, Johnston R. Occurrence of Cryptosporidium Oocysts in Leisure Pools in the UK, 2017, and Modelling of Oocyst Contamination Events. Water. 2021; 13(11):1503. https://doi.org/10.3390/w13111503

Chicago/Turabian Style

Chalmers, Rachel M., Lester P. Simmonds, Martin Wood, Megan Luxford, Rob Miller, and Rob Johnston. 2021. "Occurrence of Cryptosporidium Oocysts in Leisure Pools in the UK, 2017, and Modelling of Oocyst Contamination Events" Water 13, no. 11: 1503. https://doi.org/10.3390/w13111503

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