Risk management of waterborne Cryptosporidium in public swimming pools and splash parks in Western Australia

This thesis is a multidisciplinary approach that investigated swimming pool associated gastroenteritis outbreaks of cryptosporidiosis in Western Australia (WA), caused by the parasite Cryptosporidium, with particular emphasis on molecular epidemiology and questionnaire data. Chapter 1 is a review of the literature and statement of aims and objectives. Chapter 2 is a longitudinal study of cryptosporidiosis cases in Western Australian humans which documented the emergence of a rare C. hominis IfA12G1R5 subtype. Four species of Cryptosporidium were detected: C. hominis, C. parvum, C. meleagridis and a single case of a novel C. viatorum variant. The identification of the previously rare subtype of C. hominis, IfA12G1R5 highlights the occurrence and emergence of Cryptosporidium subtypes that could potentially cause future disease outbreaks. Chapter 3 examined the detection and characterisation of C. fayeri, a marsupial species, that caused diarrhoeal illness in a human in WA. Previous subtyping study identified C. fayeri in faecal samples from Western grey kangaroos (Macropus fuliginosus) and rabbits (Oryctolagus cuniculus) around the metro catchment areas in WA, suggesting the possibility of zoonotic transmission. Chapter 4 explored the epidemiology of two cryptosporidiosis outbreaks related to public swimming pools in the Kimberley region, in 2019 and in the Perth Metropolitan area in 2020, using molecular tools and contact tracing. Contact tracing identified that the cases were linked to particular swimming pool sources. Molecular analyses revealed the 2019 outbreak in the Kimberley region was associated mainly with the Aboriginal-associated C. hominis IdA15G1 subtype, while the larger outbreak in 2020 in WA was associated with a previously rare C. hominis IbA12G3 subtype. Multi locus sequence typing (MLST) and next generation sequencing (NGS) further revealed the strikingly different genomic epidemiology between the 2019 and 2020 cases and confirmed both outbreaks were each linked to separate swimming pool point sources. Chapter 5 assessed the knowledge, attitude and practices (KAP) of swimming pool patrons and staff. Overall, the KAPs of Cryptosporidium varied between patrons and staff but were generally limited. These knowledge gaps increase the risk of an infectious patron (or staff member) unknowingly introducing Cryptosporidium into aquatic facilities. The present study highlights that better education of the general public about the risks of cryptosporidiosis transmission is necessary. Chapter 6 tested swimming pool filter backwash and balance tank for the presence of Cryptosporidium from public swimming pools and splash parks in WA. The present study identified potential technical issues that need to be overcome prior to undertaking future studies. The findings of this thesis emphasise the importance of continued molecular surveillance of Cryptosporidium in WA and provide a foundation for future research to reduce cryptosporidiosis infections by exploring tools to improve detection and risk mitigation. Findings of the KAP of patrons and staff, and filter backwash observations can be translated into practical interventions that will improve public health