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Cryptosporidium , the most frequently reported parasite in Scotland, causes gastrointestinal illness resulting in diarrhoea, nausea and cramps. Two species are responsible for most cases: Cryptosporidium hominis (C. hominis) and Cryptosporidium parvum ( C. parvum ). Transmission occurs faecal-orally, through ingestion of contaminated food and water, or direct contact with faeces. In 2020, the COVID-19 pandemic led to global restrictions, including national lockdowns to limit viral transmission. Such interventions led to decreased social mixing, and reduced/no local and international travel, which are factors associated with transmission of multiple communicable diseases, including cryptosporidiosis. This report assessed the impact of the pandemic on Scottish cryptosporidiosis cases, and identified changes in circulating molecular variants of Cryptosporidium species. Molecular data generated using real time PCR and GP60 nested-PCR assays on laboratory-confirmed cryptosporidiosis cases reported during 2018-22 were analysed. The Scottish Microbiology Reference Laboratories (SMiRL), Glasgow, received 774 Cryptosporidium -positive faeces during 2018-22, of which 486 samples were successfully subtyped. During this time period, C. hominis ( n = 155; 21%) and C. parvum ( n = 572; 77%) were the most commonly detected species. The total number of cases during 2020, which was greatly affected by the pandemic, was markedly lower in comparison to case numbers in the 2 years before and after 2020. The most predominant C. hominis family detected prior to 2020 was the Ib family which shifted to the Ie family during 2022. The most common C. parvum variant during 2018-22 was the IIa family, however a rise in the IId family was observed ( n = 6 in 2018 to n = 25 in 2022). The dominant C. hominis subtype IbA10G2, which accounted for 71% of C. hominis subtypes in 2018-19 was superseded by three rare subtypes: IeA11G3T3 ( n = 15), IdA16 ( n = 8) and IbA9G3 ( n = 3) by 2022. Frequently reported C. parvum subtypes in 2018-19 were IIaA15G2R1 and IIaA17G1R1, accounting for 59% of total C. parvum subtypes. By 2022, IIaA15G2R1 remained the most common ( n = 28), however three unusual subtypes in Scotland emerged: IIdA24G1 ( n = 7), IIaA16G3R1 ( n = 7) and IIaA15G1R2 ( n = 7). Continuous monitoring of Cryptosporidium variants following the pandemic will be essential to explore further changes and emergence of strains with altered virulence., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Bacchetti, Connelly, Browning and Alexander.)

Cryptosporidium species are responsible for causing the majority of parasite-related gastrointestinal infections in the UK. This report describes an outbreak of 12 laboratory-confirmed cryptosporidiosis cases identified as part of a Scottish swimming pool investigation, with 9 primary and 3 secondary cases occurring over an 8-week period. Molecular speciation was successful for 11/12 cases, which revealed 10 Cryptosporidium hominis cases and 1 Cryptosporidium parvum case. Of the 10 C . hominis cases, further typing identified 7 as being an unusual sub-type, IbA6G3, which is the first description in the UK of this rare variant. The remaining three C. hominis cases were identified as the common IbA10G2 subtype. Following implementation of control measures on two occasions, no further cases were reported. This report highlights the importance of molecular typing to identify and characterize outbreaks, and emphasizes the need to adhere to swimming pool guidance. It also raises awareness of the potential for outbreaks to involve multiple species/sub-types, and emphasizes the importance of strong public health leadership to ensure effective multi-agency investigations and management of outbreaks.

Cryptosporidium parvum (C. parvum) is one of the most prevalent protozoan pathogens responsible for inducing human and animal disease worldwide. In this study, the glycoprotein-60 (gp60) subtyping tool was employed to assess the molecular diversity of C. parvum from human feces throughout Scotland during potential outbreaks. Over a 24-month period, microscopy analysis revealed 1139 positive feces containing Cryptosporidium species with 256 identified by molecular methods specifically as C. parvum. Cryptosporidium parvum was shown to be more prevalent in rural areas of Scotland and subtyping of 87 isolates demonstrated the predominant family as IIa, which occurred in 94% (n=82) of isolates. The IIaA15G1R1 subtype was most common, being isolated from 47% (n=41) of Scottish human cases. Non-IIa strains constituted a total of 5 isolates and included subtypes from the IIc, IId and IIg families. This information contributes significantly to existing knowledge and understanding of C. parvum subtypes in Scotland which is vital in assisting with the management of future local and national outbreaks.