Comparison of three cryptosporidiosis outbreaks in Western Australia: 2003, 2007 and 2011

Waterborne transmission of protozoan parasites: a review of worldwide outbreaks - an update 2017-2022

The current study presents a comprehensive review of worldwide waterborne parasitic protozoan outbreaks reported between 2017 and 2022. In total, 416 outbreaks were attributed to the waterborne transmission of parasitic protozoa. Cryptosporidium accounted for 77.4% (322) of outbreaks, while Giardia was identified as the etiological agent in 17.1% (71). Toxoplasma gondii and Naegleria fowleri were the primary causes in 1.4% (6) and 1% (4) of outbreaks, respectively. Blastocystis hominis, Cyclospora cayetanensis, and Dientamoeba fragilis were independently identified in 0.72% (3) of outbreaks. Moreover, Acanthamoeba spp., Entamoeba histolytica, Vittaforma corneae, and Enterocytozoon bieneusi were independently the causal agents in 0.24% (1) of the total outbreaks. The majority of the outbreaks (195, 47%) were reported in North America. The suspected sources for 313 (75.2%) waterborne parasitic outbreaks were recreational water and/or swimming pools, accounting for 92% of the total Cryptosporidium outbreaks. Furthermore, 25.3% of the outbreaks caused by Giardia were associated with recreational water and/or swimming pools. Developing countries are most likely to be impacted by such outbreaks due to the lack of reliable monitoring strategies and water treatment processes. There is still a need for international surveillance and reporting systems concerning both waterborne diseases and water contamination with parasitic protozoa.

Review of generic screening level assumptions for quantitative microbial risk assessment (QMRA) for estimating public health risks from Australian drinking water sources contaminated with Cryptosporidium by recreational activities

As urban communities continue to grow, demand for recreational access (including swimming) in drinking water sources have increased, yet relatively little is understood about the public health implications this poses for drinking water consumers. Preventative risk-based approaches to catchment management, informed by quantitative microbial risk assessment (QMRA), requires accurate input data to effectively model risks. A sound understanding of the knowledge gaps is also important to comprehend levels of uncertainty and help prioritise research needs. Cryptosporidium is one of the most important causes of waterborne outbreaks of gastroenteritis globally due to its resistance to chlorine. This review was undertaken by Water Research Australia to provide the most up-to-date information on current Cryptosporidium epidemiological data and underlying assumptions for exposure assessment, dose response and risk assessment for generic components of QMRA for Cryptosporidium and highlights priorities for common research. Key interim recommendations and guidelines for numerical values for relatively simple screening level QMRA modelling are provided to help support prospective studies of risks to drinking water consumers from Cryptosporidium due to body-contact recreation in source water. The review does not cover site-specific considerations, such as the levels of activity in the source water, the influence of dilution and inactivation in reservoirs, or water treatment. Although the focus is Australia, the recommendations and numerical values developed in this review, and the highlighted research priorities, are broadly applicable across all drinking source water sources that allow recreational activities.

Waterborne protozoan outbreaks: An update on the global, regional, and national prevalence from 2017 to 2020 and sources of contamination

The aim of this review is to identify the worldwide trend of waterborne protozoan outbreaks and how it varies between geographic regions during the period from 2017 to 2020. Data about waterborne protozoan outbreaks were gathered and stratified by continent, country, water source, and protozoan species associated with the outbreak. The highest prevalence of waterborne protozoan outbreaks was reported in developed countries. Out of 251 outbreaks reported worldwide during the studied period, 141, 51 and 24 outbreaks were recorded in the USA, UK, and New Zealand, respectively. These outbreaks were mainly associated with Cryptosporidium (192 outbreaks) and Giardia (48 outbreaks). Cyclospora cayetanensis, Dientamoebafragilis and Toxoplasma gondii were associated with 7 outbreaks. One outbreak was associated with each of Blastocystis hominis, Entamoeba histolytica, Microsporidia or Naegleria fowleri. This data suggests large discrepancies in the number of outbreaks reported between geographic regions, with most outbreaks recorded in developed countries. Differences in the prevalence of outbreaks between countries are likely attributed to the availability of diagnostic capabilities and surveillance programs to monitor water contamination with pathogenic protozoa. More attention and concerted efforts are required to improve water safety and to alleviate the impact of waterborne protozoan infections. Appropriate surveillance of water contamination with protozoa can enable public health officials to identify source of contamination and implement the necessary measures to limit transmission and prevent outbreaks.

Zoonoses and the Aboriginal and Torres Strait Islander population: A One Health scoping review

With limited access to animal health services, and high disease burdens among domesticated animals, Aboriginal and Torres Strait Islander communities in Australia face higher risk of disease including zoonoses. However, we lack understanding of the contribution of often preventable zoonoses to the health of these communities, which would enable us to enhance public health strategies and improve health outcomes. We conducted a scoping review to identify the current state of evidence on zoonoses in the Aboriginal and Torres Strait Islander population. We examined the size, scope and characteristics of the evidence base and analysed the zoonoses detected in the studies within a One Health framework. We identified 18 studies that detected 22 zoonotic pathogens in animals, people, and the environment, with most studies detecting pathogens in a single One Health sector and no studies investigating pathogens in all three sectors. Findings indicate that despite the strong conceptual foundations of One Health throughout the evidence base, evidence is lacking in application of this concept. There is a need to undertake further research that prioritises Aboriginal and Torres Strait Islander leadership, considers the contribution of human, animal and environmental health factors, and investigates the prevalence and impact of zoonoses in communities through a One Health approach.

A novel genotyping method for Cryptosporidium hominis

Cryptosporidiosis remains the leading protozoan induced cause of diarrhoea-associated mortality worldwide. Cryptosporidium hominis, the anthroponotically transmitted species within the Cryptosporidium genus, contributes significantly to the global burden of infection, accounting for the majority of clinical cases in many countries. This study applied high resolution melting analysis, a post-real-time PCR application, to the differentiation of six globally prevalent C. hominisgp60-subtypes. This novel method targeted three microsatellite, tandem repeat containing genetic markers, gp60, the genetic marker upon which current Cryptosporidium subtype nomenclature is based, MSB, and MSE, by which to differentiate between C. hominis isolates. This multi-locus approach successfully differentiated between all six C. hominisgp60-subtypes studied, some of which, such as IbA10G2, are known to exhibit global ubiquity. Thus, this method has the potential to be universally employed as a sensitive, cost effective and highly reproducible means to rapidly differentiate between C. hominisgp60-subtypes. Such a method would be of particular utility in epidemiological studies and outbreak scenarios, providing cost effective, clinically accessible alternative to DNA sequencing. The success of this preliminary study also supports further analysis of an expanded C. hominisgp60-subtype range and the potential expansion of the multi-locus panel in order to improve the discriminatory power of this approach.

Molecular analysis of cryptosporidiosis cases in Western Australia in 2019 and 2020 supports the occurrence of two swimming pool associated outbreaks and reveals the emergence of a rare C. hominis IbA12G3 subtype

Cryptosporidium is an important protozoan parasite and due to its resistance to chlorine is a major cause of swimming pool-associated gastroenteritis outbreaks. The present study combined contact tracing and molecular techniques to analyse cryptosporidiosis cases and outbreaks in Western Australia in 2019 and 2020. In the 2019 outbreak, subtyping at the 60 kDa glycoprotein (gp60) gene identified 89.0% (16/18) of samples were caused by the C. hominis IdA15G1 subtype. Amplicon next generation sequencing (NGS) at the gp60 locus identified five C. hominis IdA15G1 subtype samples that also had C. hominis IdA14 subtype DNA, while multi locus sequence typing (MLST) analysis on a subset (n = 14) of C. hominis samples identified three IdA15G1 samples with a 6 bp insertion at the end of the trinucleotide repeat region of the cp47 gene. In 2020, 88.0% (73/83) of samples typed were caused by the relatively rare C. hominis subtype IbA12G3. Four mixed infections were observed by NGS with three IdA15G1/ IdA14 mixtures and one C. parvum IIaA18G3R1 sample mixed with IIaA16G3R1. No genetic diversity using MLST was detected. Epidemiological and molecular data indicates that the outbreaks in 2019 and 2020 were each potentially from swimming pool point sources and a new C. hominis subtype IbA12G3 is emerging in Australia. The findings of the present study are important for understanding the introduction and transmission of rare Cryptosporidium subtypes to vulnerable populations.

Use-case scenarios for an anti-Cryptosporidium therapeutic

Cryptosporidium is a widely distributed enteric parasite that has an increasingly appreciated pathogenic role, particularly in pediatric diarrhea. While cryptosporidiosis has likely affected humanity for millennia, its recent "emergence" is largely the result of discoveries made through major epidemiologic studies in the past decade. There is no vaccine, and the only approved medicine, nitazoxanide, has been shown to have efficacy limitations in several patient groups known to be at elevated risk of disease. In order to help frontline health workers, policymakers, and other stakeholders translate our current understanding of cryptosporidiosis into actionable guidance to address the disease, we sought to assess salient issues relating to clinical management of cryptosporidiosis drawing from a review of the literature and our own field-based practice. This exercise is meant to help inform health system strategies for improving access to current treatments, to highlight recent achievements and outstanding knowledge and clinical practice gaps, and to help guide research activities for new anti-Cryptosporidium therapies.

Molecular characterization of Cryptosporidium isolates from humans in Ontario, Canada

BACKGROUND

Cryptosporidiosis is a gastrointestinal disease with global distribution. It has been a reportable disease in Canada since 2000; however, routine molecular surveillance is not conducted. Therefore, sources of contamination are unknown. The aim of this project was to identify species and subtypes of Cryptosporidium in clinical cases from Ontario, the largest province in Canada, representing one third of the Canadian population, in order to understand transmission patterns.

METHODS

A total of 169 frozen, banked, unpreserved stool specimens that were microscopy positive for Cryptosporidium over the period 2008-2017 were characterized using molecular tools. A subset of the 169 specimens were replicate samples from individual cases. DNA was extracted directly from the stool and nested PCR followed by Sanger sequencing was conducted targeting the small subunit ribosomal RNA (SSU) and glycoprotein 60 (gp60) genes.

RESULTS

Molecular typing data and limited demographic data were obtained for 129 cases of cryptosporidiosis. Of these cases, 91 (70.5 %) were due to Cryptosporidium parvum and 24 (18.6%) were due to Cryptosporidium hominis. Mixed infections of C. parvum and C. hominis occurred in four (3.1%) cases. Five other species observed were Cryptosporidium ubiquitum (n = 5), Cryptosporidium felis (n = 2), Cryptosporidium meleagridis (n = 1), Cryptosporidium cuniculus (n = 1) and Cryptosporidium muris (n = 1). Subtyping the gp60 gene revealed 5 allelic families and 17 subtypes of C. hominis and 3 allelic families and 17 subtypes of C. parvum. The most frequent subtype of C. hominis was IbA10G2 (22.3%) and of C. parvum was IIaA15G2R1 (62.4%).

CONCLUSIONS

The majority of isolates in this study were C. parvum, supporting the notion that zoonotic transmission is the main route of cryptosporidiosis transmission in Ontario. Nonetheless, the observation of C. hominis in about a quarter of cases suggests that anthroponotic transmission is also an important contributor to cryptosporidiosis pathogenesis in Ontario.

Species and genotypes causing human cryptosporidiosis in New Zealand

Cryptosporidium is one of the most common causes of diarrhoea around the world. Successful management and prevention of this infectious disease requires knowledge of the diversity of species and subtypes causing human disease. We use sequence data from 2598 human faecal samples collected during an 11-year period (2009-2019) to better understand the impact of different species and subtypes on public health and to gain insights into the variation of human cryptosporidiosis in New Zealand. Human cryptosporidiosis in New Zealand is caused by a high diversity of species and subtypes. Six species cause human disease in New Zealand: C. hominis, C. parvum, C. cuniculus, C. erinacei, C. meleagridis and C. tyzzeri. Sequence analysis of the gp60 gene identified 16 subtype families and 101 subtypes. Cryptosporidium hominis IbA10G2 and C. parvum IIaA18G3R1 were the most frequent causes of human cryptosporidiosis with 27% and 29% of infections, respectively. Cryptosporidium hominis presented a peak of notified human cases during autumn (March-May) whereas most cases of human cryptosporidiosis caused by C. parvum are found during the calving and lambing season in spring (September-November). We also reported some subtypes that have been rarely detected in other countries such as IbA20G2 and IIoA13G1 and a low prevalence of the hypertransmissible and virulent IIaA15G2R1. This study provides insight into the variability of cryptosporidiosis in New Zealand essential for disease management and surveillance to prevent the introduction or spread of new species and subtypes in the country.

Cryptosporidium hominis infections in non-human animal species: revisiting the concept of host specificity

Parasites in the genus Cryptosporidium, phylum Apicomplexa, are found worldwide in the intestinal tract of many vertebrate species and in the environment. Driven by sensitive PCR methods, and the availability of abundant sequence data and reference genomes, the taxonomic complexity of the genus has steadily increased; 38 species have been named to date. Due to its public health importance, Cryptosporidium hominis has long attracted the interest of the research community. This species was initially described as infectious to humans only. This perception has persisted in spite of an increasing number of observations of natural and experimental infections of animals with this species. Here we summarize and discuss this literature published since 2000 and conclude that the host range of C. hominis is broader than originally described. The evolving definition of the C. hominis host range raises interesting questions about host specificity and the evolution of Cryptosporidium parasites.

Association between Cryptosporidium infection and cancer: A systematic review and meta-analysis

The link between cryptosporidiosis and cancer has been suggested by some epidemiological studies. This systematic review and meta-analysis was conducted to further understand this relationship. In the current study, six electronic databases were reviewed for Cryptosporidium infection in cancer patients. We used random effects model and 95% confidence intervals (CI) to determine the overall odds ratio (OR). Heterogeneity was calculated with Cochran's Q test and I²statistic. In total, 19 studies involving 3562 individuals with case-control (nine) and cross-sectional (ten) designs were included in our project. The pooled overall random effect favored a statistically significant increased risk of Cryptosporidium infection in cancer patients compared with non-cancer individuals [OR = 3.3; 95% CI: 2.18-4.98]. The overall heterogeneity was medium (χ² = 25.77; I² = 30.2%, P = .11). The pooled ORs in case-control and cross-sectional studies were [OR = 5.60; 95% CI: 3.43-9.13; χ² = 5.51; I² = 0.00%, P = .70] and [OR = 2.08; 95% CI: 1.18-3.67; χ² = 13.69; I² = 34.3, P = .13], respectively. T-value and P-value were 0.54 and 0.57 based on the results of Harbord's modified's regression test. In summary, this meta-analysis demonstrates that Cryptosporidium infection is associated with cancer. Also, it found that study design and year of publication are the specific sources of heterogeneity. Further studies should be carried out to investigate the impact of Cryptosporidium infection in the onset or development of cancer in the future.

Molecular epidemiology of Giardia and Cryptosporidium infections - What's new?

New information generated since 2016 from the application of molecular tools to infections with Giardia and Cryptosporidium is critically summarised. In the context of molecular epidemiology, nomenclature, taxonomy, in vitro culture, detection, zoonoses, population genetics and pathogenicity, are covered. Whole genome sequencing has had the greatest impact in the last three years. Future advances will provide a much better understanding of the zoonotic potential of both parasites, their diversity and how this is linked to pathogenesis in different hosts.

Retrospective analysis of Cryptosporidium species in Western Australian human populations (2015-2018), and emergence of the C. hominis IfA12G1R5 subtype

Cryptosporidium species are a major cause of diarrhoea worldwide. In the present study, a retrospective analysis of 109 microscopically Cryptosporidium-positive faecal specimens from Western Australian patients, collected between 2015 and 2018 was conducted. Sequence analysis of the 18S rRNA and the 60 kDa glycoprotein (gp60) gene loci identified four Cryptosporidium species: C. hominis (86.2%, 94/109), C. parvum (11.0%, 12/109), C. meleagridis (1.8%, 2/109) and C. viatorum (0.9%, 1/109). Subtyping at the gp60 locus identified a total of 11 subtypes including the emergence of the previously rare C. hominis IfA12G1R5 subtype in 2017 as the dominant subtype (46.7%, 21/45). This subtype has also recently emerged as the dominant subtype in the United States but the reasons for its emergence are unknown. This is also the first report of C. viatorum in humans in Australia and a novel subtype (XVaA3g) was identified in the one positive patient.