Cryptosporidiosis and filtration of water from Loch Lomond, Scotland

Application of QMRA to prioritise water supplies for Cryptosporidium risk in New South Wales, Australia

A Quantitative Microbial Risk Assessment (QMRA) framework was applied to assess 312 drinking water supply systems across regional New South Wales (NSW). The framework was needed to support the implementation of a recommendation in the Australian Drinking Water Guidelines (ADWG) for appropriate treatment barriers to be operating in systems 'at risk' for Cryptosporidium. The objective was to prioritise systems so that those with the highest risk could be identified and addressed first. The framework was developed in a pilot study of 30 systems, selected to represent the range of water supplies across regional NSW. From these, source water categories were defined to represent local conditions with reference to the literature and Cryptosporidium risk factors. Values for Cryptosporidium oocyst concentration were assigned to the categories to allow quantification of the health risk from those water sources. The framework was then used to assess the risks in all 312 regional drinking water supply systems. Combining the disciplined approach of QMRA with simple catchment and treatment information and categorical risk outputs provided a useful and transparent method for prioritising systems for further investigation and potential risk management intervention. The risk rankings for drinking water supplies from this QMRA process have been used to set priorities for a large State Government funding program.

Endemic gastrointestinal illness and change in raw water source and drinking water production - A population-based prospective study

There are indications that drinking water may contribute to endemic gastrointestinal illness (GII) even when the drinking water quality meets current standards, but the knowledge is limited. In this population-based prospective study, we assessed if changes in municipal drinking water production affected the GII incidence, by collecting self-reported GII episodes among the population in two municipalities during calendar time-specific inter-annual periods. About 2600 adults in central Sweden and 2600 adults (including 700 households with children aged 0-9 years) in Southwest Sweden, were followed during a baseline and a follow-up period in 2012-2016. Monthly reports of episodes and symptoms of GII were collected by SMS. The following drinking water related changes were assessed: Change 1 (adults); a municipality with a groundwater treatment, changed to a different groundwater source with UV treatment; Change 2 (adults); a municipality with a surface water treatment changed to a groundwater source with UV treatment; and Change 3a (adults) and 3b (children): a municipality with a surface water treatment changed to a new surface water source, having a treatment with a higher pathogen reduction. We observed no evidence that changes in raw water source and/or improved pathogen removal in the drinking water treatment affected the risk of GII among adults. Among children aged 0-9 years participating in Change 3b, we observed a 24% relative risk reduction in GII incidence. These results suggest that improved water treatment may reduce the disease burden of GII in children even in settings in which water treatment efficacy meets current quality standards.

Development and application of DNA-aptamer-coupled magnetic beads and aptasensors for the detection of Cryptosporidium parvum oocysts in drinking and recreational water resources

Environmentally stable and disinfectant-resistant oocysts of Cryptosporidium spp. shed in the feces of infected humans and animals frequently contaminate water resources and are subsequently spread via potable and recreational waters. The current monoclonal-antibody-based methods for detecting them in water are slow, labor-intensive, and demand skills to interpret the results. We have developed DNA-aptamer-based aptasensors, coupled with magnetic beads, to detect and identify the oocysts of C. parvum for monitoring recreational and drinking water sources. A sensitive and specific electrochemical aptasensor (3'-biotinylated R4-6 aptamer) was used as a secondary ligand to bind the streptavidin-coated magnetic beads. This was incorporated into a probe using gold nanoparticle modified screen-printed carbon electrodes. Square wave voltammetry allowed for specific recognition of C. parvum oocysts. The aptamer-coated probes had an oocyst detection limit of 50. It did not bind to the cysts of Giardia duodenalis, another common waterborne pathogen, thus indicating its high specificity for the target pathogen. The system could successfully detect C. parvum oocysts in spiked samples of the raw lake and river waters. Therefore, the combined use of the aptasensor and magnetic beads has the potential to monitor water quality for C. parvum oocysts in field samples without relying on monoclonal antibodies and skill-demanding microscopy.

Exposures associated with infection with Cryptosporidium in industrialised countries: a systematic review protocol

BACKGROUND

Cryptosporidium is a protozoan parasite of humans and other animals worldwide and is one of the greatest contributors to human diarrhoeal illness. Transmission can occur indirectly via contaminated food or water, or directly via contact with animals or other infected people. Risk exposures are often identified from outbreak investigations, but a subset of cases remains unexplained, and sources for sporadic disease and pathways to infection are still unclear. Given the few systematic syntheses of reported evidence in industrialised populations, the aim of this review is to consolidate the literature to describe exposures associated with human cryptosporidiosis in industrialised countries, specifically including the UK, and describe any differences between outbreak-associated and sporadic disease.

METHODS/DESIGN

Where relevant, methods will follow the recommendations made in the Cochrane Handbook for Systematic Reviews of Interventions. Three steps will be used to identify the literature including electronic database searching using PubMed, Scopus, Embase and Web of Science; reference list trawling; and an exploration of the grey literature. Screening of results will be undertaken by two reviewers using pre-defined criteria. Studies conducted in industrialised countries and reporting on human subjects will be included. All observational studies will be included where they report exposures and relevant quantitative results. Data will be extracted using a standardised form. Study quality will be assessed using the ROBINS-I tool. Data will be summarised presenting the papers' main findings including population under study, outcomes, and exposures, and whether these were considered outbreak or sporadic cases. A narrative summary will also be included. Where populations are appropriate, available data will be pooled in a meta-analysis combining the significant exposures across studies.

DISCUSSION

This review aims to consolidate the evidence for transmission routes and exposures for Cryptosporidium in industrialised countries, with particular reference to how these may apply to the UK. In addition, the review will seek to describe differences between outbreak and sporadic cases. This will help to identify those most vulnerable, highlighting pathways where interventions and public health response may be appropriate.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO number CRD42017056589 .

Measuring sporadic gastrointestinal illness associated with drinking water - an overview of methodologies

There is an increasing awareness that drinking water contributes to sporadic gastrointestinal illness (GI) in high income countries of the northern hemisphere. A literature search was conducted in order to review: (1) methods used for investigating the effects of public drinking water on GI; (2) evidence of possible dose-response relationship between sporadic GI and drinking water consumption; and (3) association between sporadic GI and factors affecting drinking water quality. Seventy-four articles were selected, key findings and information gaps were identified. In-home intervention studies have only been conducted in areas using surface water sources and intervention studies in communities supplied by ground water are therefore needed. Community-wide intervention studies may constitute a cost-effective alternative to in-home intervention studies. Proxy data that correlate with GI in the community can be used for detecting changes in the incidence of GI. Proxy data can, however, not be used for measuring the prevalence of illness. Local conditions affecting water safety may vary greatly, making direct comparisons between studies difficult unless sufficient knowledge about these conditions is acquired. Drinking water in high-income countries contributes to endemic levels of GI and there are public health benefits for further improvements of drinking water safety.

A Bibliometric and Trend Analysis on the Water-Related Risk Assessment Studies for Cryptosporidium Pathogen

BACKGROUND

The bibliometric methods have been used in many disciplines of sciences to study the scientific production and research trends. In this study, they were used to investigate research trends related to the risk assessment of Cryptosporidium pathogen in water field.

METHODS

Data were obtained on the Scopus database from 1993 to 2013. Research tendency was investigated by analyzing the distribution of languages, countries, journals, author keywords, authorship pattern and co-authorship relations.

RESULTS

The English language was dominant language of all publications (96.36%). Number of articles in this field increased from 2 in 1993 to 29 papers in 2007 and then received to 19 at the end of 2013. United States produced 35.41% of all pertinent articles followed by United Kingdom with 10.76% and Australia with 9.92%. Water Research Journal published the most papers in this field, taking 11.62% of all, followed by Journal of Water and Health (10.92%) and Water Science and Technology (10.21%). The most productive authors were Ashbolt NJ form Canada that accounts about 1.51% of the total publications followed by Rose JB and Haas CN from United States. Authorship pattern analysis results show that literature does follow Lotka's law (P=0.627).

CONCLUSION

A downward trend in the number of publications is likely to occur in future. The results of this bibliometric analysis may help relevant researchers realize the scope of the microbial risk assessment research of Cryptosporidium, and establish the further research direction.

Effects of drinking-water filtration on Cryptosporidium seroepidemiology, Scotland

Improved filtration is associated with reduced prevalence of antibodies against Cryptosporidium spp.

Continuous exposure to low levels of Cryptosporidium oocysts is associated with production of protective antibodies. We investigated prevalence of antibodies against the 27-kDa Cryptosporidium oocyst antigen among blood donors in 2 areas of Scotland supplied by drinking water from different sources with different filtration standards: Glasgow (not filtered) and Dundee (filtered). During 2006–2009, seroprevalence and risk factor data were collected; this period includes 2007, when enhanced filtration was introduced to the Glasgow supply. A serologic response to the 27-kDa antigen was found for ≈75% of donors in the 2 cohorts combined. Mixed regression modeling indicated a 32% step-change reduction in seroprevalence of antibodies against Cryptosporidium among persons in the Glasgow area, which was associated with introduction of enhanced filtration treatment. Removal of Cryptosporidium oocysts from water reduces the risk for waterborne exposure, sporadic infections, and outbreaks. Paradoxically, however, oocyst removal might lower immunity and increase the risk for infection from other sources.

Reduction in cryptosporidiosis associated with introduction of enhanced filtration of drinking water at Loch Katrine, Scotland

Previous evidence has suggested an association between cryptosporidiosis and consumption of unfiltered drinking water from Loch Katrine in Scotland. Before September 2007, the water was only micro-strained and chlorinated; however, since that time, coagulation and rapid gravity filtration have been installed. In order to determine risk factors associated with cryptosporidiosis, including drinking water, we analysed data on microbiologically confirmed cases of cryptosporidiosis from 2004 to 2010. We identified an association between the incidence of cryptosporidiosis and unfiltered Loch Katrine drinking water supplied to the home (odds ratio 1.86, 95% confidence interval 1.11-3.11, P = 0.019). However, while filtration appears to be associated with initially reduced rates of cryptosporidiosis, evidence suggests it may paradoxically make those consumers more susceptible to other transmission routes in the long-term. These findings support implementation of similar treatment for other unfiltered drinking-water supplies, as a means of reducing cryptosporidiosis associated with drinking water.

Spatial and temporal epidemiology of sporadic human cryptosporidiosis in Scotland

The spatial and temporal epidemiology of human cryptosporidiosis was described by analysing sporadic cases reported in Scotland from 2005 to 2007. Measures of livestock density and human population density were explored as indicators of the geographical variation in prevalence. Cryptosporidium parvum was more common in areas with lower human population densities, with a higher ratio of the number of farms to human inhabitants and with a higher ratio of the number of private water supplies to human inhabitants. Cryptosporidium parvum caused disease in humans in rural areas and in areas with high ruminant livestock density, whereas Cryptosporidium hominis was more common in the more densely human populated areas of Scotland. The association of private water supplies and increased Cryptosporidium reports merits further public health efforts.

Quantitative risk assessment of Cryptosporidium in tap water in Ireland

Cryptosporidium species are protozoan parasites associated with gastro-intestinal illness. Following a number of high profile outbreaks worldwide, it has emerged as a parasite of major public health concern. A quantitative Monte Carlo simulation model was developed to evaluate the annual risk of infection from Cryptosporidium in tap water in Ireland. The assessment considers the potential initial contamination levels in raw water, oocyst removal and decontamination events following various process stages, including coagulation/flocculation, sedimentation, filtration and disinfection. A number of scenarios were analysed to represent potential risks from public water supplies, group water schemes and private wells. Where surface water is used additional physical and chemical water treatment is important in terms of reducing the risk to consumers. The simulated annual risk of illness for immunocompetent individuals was below 1 x 10(-4) per year (as set by the US EPA) except under extreme contamination events. The risk for immunocompromised individuals was 2-3 orders of magnitude greater for the scenarios analysed. The model indicates a reduced risk of infection from tap water that has undergone microfiltration, as this treatment is more robust in the event of high contamination loads. The sensitivity analysis highlighted the importance of watershed protection and the importance of adequate coagulation/flocculation in conventional treatment. The frequency of failure of the treatment process is the most important parameter influencing human risk in conventional treatment. The model developed in this study may be useful for local authorities, government agencies and other stakeholders to evaluate the likely risk of infection given some basic input data on source water and treatment processes used.

Massive outbreak of viral gastroenteritis associated with consumption of municipal drinking water in a European capital city

On 24 August 2008, an outbreak alert regarding cases of acute gastroenteritis in Podgorica triggered investigations to guide control measures. From 23 August to 7 September, 1699 cases were reported in Podgorica (population 136 000) and we estimated the total size of the outbreak to be 10 000-15 000 corresponding to an attack rate of approximately 10%. We conducted an age- and neighbourhood-matched case-control study, microbiologically analysed faecal and municipal water samples and assessed the water distribution system. All cases (83/83) and 90% (80/90) [corrected] of controls drank unboiled chlorinated municipal water [matched odds ratio (mOR) 11.2, 95% confidence interval (CI), 1.6-infinity]. Consumption of bottled water was inversely associated with illness (mOR 0.3, 95% CI 0.1-0.8). Analyses of faecal samples identified six norovirus genotypes (21/38 samples) and occasionally other viruses. Multiple defects in the water distribution system were noted. These results suggest that the outbreak was caused by faecally contaminated municipal water. It is unusual to have such a large outbreak in a European city especially when the municipal water supply is chlorinated. Therefore, it is important to establish effective multiple-barrier water-treatment systems whenever possible, but even with an established chlorinated supply, sustained vigilance is central to public health.

GiardiaandCryptosporidiuminfections in sheep and goats: a review of the potential for transmission to humans via environmental contamination

The public health significance of giardiasis and cryptosporidiosis in sheep is currently unclear. Some research suggests that they are probably not an important zoonotic reservoir, whilst other research indicates this potential exists, and some outbreaks have also been associated with infections in sheep. Actions to limit water supply contamination by sheep have sometimes been severe, occasionally creating problems between farming and public health communities. Here our knowledge on these parasites in both sheep and goats is reviewed; although direct evidence of transmission to humans via water supply contamination is limited, the data accrued indicate that this is a real possibility. As cryptosporidiosis in sheep is generally more prevalent than giardiasis, and species/genotypes ofCryptosporidiuminfections in sheep are likely to be infectious to humans, this parasite may be considered the greater threat. Nevertheless, geographical variation in prevalence and genotypic distribution is extensive and as measures to limit sheep grazing can have a highly negative impact, it is important that cases are judged individually. If water contamination from a particular population of sheep/goats is suspected, then suitable investigations should be instigated, investigating both prevalence and species/genotype, before precautionary measures are imposed.