Quantitative microbial risk assessment of Cryptosporidium and Giardia in well water from a native community of Mexico

Change in the incidence of intestinal diseases caused by parasitic protozoa in the Mexican population during the period (2015-2019) and its association with environmental and socioeconomic risk factors

Diarrheal diseases are one of the main health problems worldwide, especially in developing countries with poor health systems, high rates of poverty, and poor nutrition. The main causative agents of diarrheal disease are bacteria, viruses, and parasites; among the latter, the intestinal protozoa Giardia and Entamoeba stand out. In the present work, a observational analysis of the national surveillance data of amebiasis, giardiasis, and other protozoan intestinal infections was carried out. The data issued by the Directorate General of Epidemiology was analyzed to establish its relationship with geography, socioeconomic, and environmental conditions in Mexico during the 2015-2019 period. New cases of amebiasis decreased by 25.03% between 2015 and 2019, while giardiasis and other protozoan intestinal infections remained constant; in all cases, incidence was higher in females than in males, and children under 5 years of age were the most affected. The contribution of environmental conditions (seasonality, temperature, and humidity) and socioeconomic factors in the number of protozoan intestinal infection cases was assessed by a multivariable regression model using a backward selection procedure. Peaks in cases were observed in spring and summer, which are characterized by warm and humid climates. Additionally, states with high humidity and annual average temperature contribute to a notably higher incidence of these parasites, especially annual average temperature, as demonstrated through multivariable linear regression models. Moreover, the majority of these states have the largest population living in poverty with inadequate measures for the distribution, dispensing, and sanitation of water. These data are essential to incidence rate monitoring and focus efforts on eliminating risk factors and improving health programs in Mexico.

Assessing the risk of acute gastrointestinal illness attributable to three enteric pathogens from contaminated private water wells in Ontario

The province of Ontario compromises the largest groundwater reliant population in Canada serving approximately 1.6 million individuals. Unlike municipal water systems, private well water is not required to meet water quality regulatory standards and thus source maintenance, treatment and testing remains the responsibility of the well owner. Infections associated with private drinking water systems are rarely documented given their typically sporadic nature, thus the human health effects (e.g., acute gastrointestinal illness (AGI)) on consumers remains relatively unknown, representing a significant gap in water safety management. The current study sought to quantify the risk of waterborne AGI attributed to Giardia, shiga-toxin producing E. coli (STEC) and norovirus from private drinking water sources in Ontario using Monte Carlo simulation-based quantitative microbial risk assessment (QMRA). Findings suggest that consumption of contaminated private well water in Ontario is responsible for approximately 4823 AGI cases annually, with 3464 (71.8%) and 1359 (28.1%) AGI cases predicted to occur in consolidated and unconsolidated aquifers, respectively. By pathogen, waterborne AGI was attributed to norovirus (62%; 2991/4823), Giardia (24.6%; 1186/4823) and STEC (13.4%; 646/4823). The developed QMRA framework was used to assess the potential health impacts of partial and total well water treatment system failure. In the unlikely event of total treatment failure, total mean annual illnesses are predicted to almost double (4217 to 7064 cases per year), highlighting the importance of effective water treatment and comprehensive testing programs in reducing infectious health risks attributable to private well water in Ontario. Study findings indicate significant underreporting of waterborne AGI rates at the provincial level likely biasing public health interventions and programs that are effective in monitoring and minimizing the health risk associated with private well water.

Assessment microbial risks for the presence of Cryptosporidium spp. and Giardia spp. based on the surveillance of the water supply systems in Colombia, 2014-2018

Cryptosporidium spp. and Giardia spp. cause gastrointestinal diseases of zoonotic origin as well transmitted from person to person, being various reported outbreaks associated with water. The infecting (oo)cyst forms of these parasites are highly resistant to water treatments such as chlorine disinfection and fast filtration. The objective of this study was to assess the microbial risk of infection and symptomatic illness by the ingestion of Giardia spp. and Cryptosporidium spp. in water for human consumption in Colombia, based on the results of water quality surveillance. The detection method was according to the USEPA method 1623. Concentration data of the different points of distribution were grouped according to the pathogen and type of treatment (no treatment; chlorine treatment; chlorine treatment + coagulant). Annual microbial risks of infection and symptomatic diseases were estimated using the quantitative microbial risk assessment approach that included parasite concentrations, the dose-response model, the ingestion rates of water by children and adults, and the morbidity rate of the diseases. The mean annual microbial risk of infection for Giardia spp. was 29.8% for treated water and 50.4% for untreated water, while being 6.0% and 17.7%, respectively, for Cryptosporidium spp. Microbial risk of symptomatic illness for Giardia spp, was 8.2% for treated water and 13.9% for untreated water, while being 3.6% and 10.6%, respectively, for Cryptosporidium spp. The estimated annual microbial risks of infection exceeded the acceptable value of 10^-4 (0.01%) recommended by USEPA. Results obtained in this study suggest the need to reduce the microbial risk of infection to protozoan parasites by improving the water treatment, by adopting better handling practices for livestock manure and treatment processes of human feces. PRACTITIONER POINTS: The presence of Cryptosporidium spp was identified in 28 (6.2%) samples and Giardia spp in 29 (6.4%) in water for human consumption in Colombia. The mean annual risk of symptomatic illness due to infection by Giardia spp or Cryptosporidium spp ranges from 33.6%, for treated water, to 58.1%, for untreated water. Annual risks ingestion of protozoa studying in water for human exceed of 10-4 (0.01%) recommended by USEPA.

Nutritional status, intestinal parasitic infections, and socio-environmental conditions in Mbyá-guaraní children: The current situation in communities in central Misiones, Argentina

OBJECTIVES

Our previous research in Mbyá-guaraní communities of central Misiones showed high levels of growth stunting and intestinal parasites in children, as well as associations between these variables and deficient sanitary conditions. New studies were necessary to update the present health status of the previously studied Mbyá populations after around two decades. Therefore, we evaluated the current nutritional status, intestinal parasites, and socio-environmental conditions among Mbyá-guaraní children from these communities.

METHODS

Body weight and height of 102 individuals (aged 2-14) were measured and nutritional status was estimated according to the World Health Organization criteria. Serial fecal samples and anal swabs were analyzed from 75 children (aged 1-14). Socio-environmental data were obtained from questionnaires.

RESULTS

The prevalence of undernutrition was 31.4% and excess of weight was 10.8%. The prevalence of stunting and of overweight reached 30.4% and 8.8%, respectively. About 85% of the children were infected with at least one of the 14 species identified, and around 44% had multiple parasite infections. The most prevalent species were Enterobius vermicularis and hookworms. Among undernourished children, 88.2% were parasitized by at least one of the potentially pathogenic species detected. Most of the families lived in overcrowded conditions in precarious houses, defecated in latrines, and consumed well water. A higher risk of parasitosis was associated with the source of drinking water.

CONCLUSIONS

Although the prevalence of undernutrition and intestinal parasites decreased compared with our previous studies, we still observed the coexistence of stunting, excess weight, and parasitic infections, in a context of socio-environmental vulnerability.

Cryptosporidium and Giardia in Biogas Wastewater: Management of Manure Livestock and Hygiene Aspects Using Influent, Effluent, Sewage Canal Samples, Vegetable, and Soil Samples

Cryptosporidium and Giardia are two water- and foodborne protozoan parasites that can cause diarrheal diseases. Poor microbial quality, sanitation conditions, and hygiene practices at exposure to biogas wastewater are important risk factors for human and animal infection. This study highlights the presence and level of both parasites in the environment in relation to biogas waste reuse in Vietnam. A total of 239 samples were collected from different types of samples in the studied districts in Bac Giang province in 2020 via direct immunofluorescent detection to study the occurrence of Cryptosporidium spp. and Giardia spp. (oo)cysts. Among the samples, Cryptosporidium was found in 19 (7.9%) with concentration from 1.104 to 3.105 oocysts/100 mL, while Giardia in 40 (16.7%) with concentration from 1.104 to 2.106 cysts/100 mL, respectively. In detail, the results show that the percentages of positive detection of Cryptosporidium spp. and Giardia spp. in influent, effluent, sewage canal, and vegetables were 13.1% (11/84), 6.0% (5/83), 15.4% (2/13) and 5.9% (1/17) and 26.2% (22/84), 7.2% (6/83), 7.7% (1/13) and 5.9% (1/17), respectively. The results show a trend of decreasing Cryptosporidium and Giardia densities, without statistical significance. Although these parasites decreased after biogas treatment, the remaining loads observed in biogas effluent can reach the watercourses and soil receiving it. Further investigations are needed to contribute to a general understanding of the risk of protozoan parasites, as well as strategies to control and reduce the contamination of environmental water sources and plants and reduce the burden of the pathogens in biogas wastewater in Vietnam.

Pre-ozonation of surface water: An effective water treatment process to reduce the risk of infection by Giardia in drinking water

Giardia is a protozoan parasite of primary concern for the drinking water industry. High contact times are required for Giardia inactivation by chlorination, while ozonation may be effective at much lower Ct products. In this study, we have assessed the occurrence of Giardia cysts in raw water, and in chlorinated or ozonated water from a drinking water treatment plant (DWTP) in Brazil, over a 16-month period. Moreover, we analyzed the effects of primary disinfection on cysts, and calculated the infection risk caused by the occurrence of Giardia cysts in raw water, chlorinated or ozonated water. Furthermore, we assessed the correlation of Giardia cysts with indicator bacteria in raw water. Data referring to concentration of Giardia cysts in raw water showed adherence to a gamma distribution at a significance level α = 0.05. The detection frequency and the mean concentration of Giardia cysts were higher in raw water (86.6%, 26 cysts∙L^-1), than in chlorinated (46.1%, 15.7 cysts·L^-1) or ozonated water (43.5%, 11.1 cysts·L^-1). Overall, Giardia non-viable cysts were detected more frequently in ozonated water (80%) than in chlorinated water (68.2%) or raw water (37.7%). Ozonation and chlorination resulted, respectively, in ≈27.5- and ≈13- fold reduction of Giardia infection risk, when compared to the risk calculated for raw water. Total coliform and Escherichia coli proved to be suitable surrogates to predict the occurrence of Giardia cysts in raw surface water, however, the indicator bacteria may not be suitable surrogates to predict the disinfection of Giardia cysts, as no correlation was found between indicator bacteria and Giardia cysts in treated water. To our knowledge, this is the first study reporting the efficacy of chlorine and ozone at Ct products actually applied at a full-scale drinking water treatment plant against Giardia cysts naturally occurring in the source water, i.e. real situation. Ozonation has proven more efficient than chlorination against Giardia cysts in surface water. Escherichia coli proved to be suitable surrogate to predict Giardia cysts in raw surface water.

Cryptosporidium spp. in groundwater supplies intended for human consumption - A descriptive review of global prevalence, risk factors and knowledge gaps

Cryptosporidiosis is one of the leading causes of diarrhoeal illness and mortality induced by protozoan pathogens worldwide. As a largely waterborne disease, emphasis has been given to the study of Cryptosporidium spp. in surface waters, readily susceptible to pathogenic contamination. Conversely, the status of Cryptosporidium in potable groundwater sources, generally regarded as a pristine and "safe" drinking-water supply owing to (sub)-soil protection, remains largely unknown. As such, this investigation presents the first literature review aimed to ascertain the global prevalence of Cryptosporidium in groundwater supply sources intended for human consumption. Thirty-seven peer-reviewed studies were identified and included in the review. Groundwater sample and supply detection rates (estimated 10-20%) indicate Cryptosporidium is frequently present in domestic groundwater sources, representing a latent health concern for groundwater consumers. Specifically, sample (10.4%) and source (19.1%) detection rates deriving from comprehensive "temporal" investigations are put forward as representative of a contamination 'baseline' for Cryptosporidium in 'domestic' groundwater supplies. Proposed 'baseline' prevalence figures are largely applicable in preventive risk-based catchment and groundwater quality management including the formulation of Quantitative Microbial Risk Assessment (QMRA). Notwithstanding, a large geographical disparity in available investigations and lack of standardized reporting restrict the transferability of research findings. Overall, the mechanisms responsible for Cryptosporidium transport and ingress into groundwater supplies remain ambiguous, representing a critical knowledge gap, and denoting a distinctive lack of integration between groundwater and public-health sub-disciplines among investigations. Key recommendations and guidelines are provided for prospective studies directed at more integrative and multi-disciplinary research.

Cryptosporidium and Giardia in urban wastewater: A challenge to overcome

This study aimed to quantify Giardia and Cryptosporidium in disinfected water reuse samples from two Wastewater Treatment Plants (A and B), which were quantified by USEPA 1693/2014 Method. Giardia was found in 35.8% of the total samples (<0.03 to 16 cysts/L) while Cryptosporidium in 30.2% (<0.03 to 25.8 oocysts/L). This study highlights the presence of both parasites in water for reuse despite treatment processes for their removal, which means there is a challenge to overcome. Their presence is preoccupant even though in low concentrations because the infectivity dose is low coupled with high prevalence in the global population. The practice of water recycling is valuable for sustainable water management and it is in line with Sustainable Developments Goals but should not threaten human health. Tackling this issue is more critical in developing countries because treatment processes are often more limited, the monitoring data from water reuse are not always available, the lack of regulation for water reuse quality and the lack of planning for its sustainable usage.

Quantitative Microbial Risk Assessment and Infectious Disease Transmission Modeling of Waterborne Enteric Pathogens

PURPOSE OF REVIEW

Waterborne enteric pathogens remain a global health threat. Increasingly, quantitative microbial risk assessment (QMRA) and infectious disease transmission modeling (IDTM) are used to assess waterborne pathogen risks and evaluate mitigation. These modeling efforts, however, have largely been conducted independently for different purposes and in different settings. In this review, we examine the settings where each modeling strategy is employed.

RECENT FINDINGS

QMRA research has focused on food contamination and recreational water in high-income countries (HICs) and drinking water and wastewater in low- and middle-income countries (LMICs). IDTM research has focused on large outbreaks (predominately LMICs) and vaccine-preventable diseases (LMICs and HICs). Human ecology determines the niches that pathogens exploit, leading researchers to focus on different risk assessment research strategies in different settings. To enhance risk modeling, QMRA and IDTM approaches should be integrated to include dynamics of pathogens in the environment and pathogen transmission through populations.

The Prevalence of Intestinal Parasite Infection in El Behara Schoolchildren

This study was conducted to evaluate the prevalence of intestinal parasite in schoolchildren in Damanhur, Egypt and some of its villages. The pathogenic enteric protozoa have been progressively involved in bargaining the soundness of a great many individuals, for the most part in creating nations. Mediations are being set up to control the dreariness and mortality because of these protozoan contaminations. A portion of these mediations target school going kids with regards to class based wellbeing intercession. The present examination concentrated on exploring the commonness of intestinal protozoan contaminations among younger students chose networks comprising of urban, urban-poor and per urban settlements in the Damanhour and a few towns. In the present work Giardia lamblia was the second usually identified protozoan with a diseases rate 10.4% among the analyzed cases. In the present examination generally speaking level of parasitic contaminations among the kids was 57.3%. It's viewed as Enterobius vermicularis was the most usually identified protozoan as it spoke to 4.1% of the parasitic diseases in the considered cases pursued by Ascaris lumbricoides; 1.4% and Giardia lamblia contaminations as they spoke to 0.6%; separately. The protozoa like Giardia and Cryptosporidium are regularly present in surface waters and cause episodes in this manner legitimately affecting human wellbeing.

Quantitative microbial risk assessment and its applications in small water systems: A review

Quantitative microbial risk assessment (QMRA) has been mainstreamed in many large municipal water systems as part of a paradigm shift in the drinking water industry towards water safety planning and risk-based system assessment. Small water systems (SWSs) are generally more vulnerable to typical water system hazards, and consequently have a higher risk of waterborne disease outbreak. In this paper, a review of experiences in implementing QMRA in SWSs helps elaborate the sources of risks and highlights some of the challenges facing SWSs in developed countries. A critical review of the important elements for practical implementation of QMRA was conducted. The investigation focuses on aspects related to challenges in identifying relevant hazards to SWSs to create failure scenarios, acquiring monitoring data for pathogens' concentrations in source water, estimating treatment efficiencies of typical small system technologies, and access to software tools to support successful implementation. The review helped outline ways through which SWSs can overcome the identified challenges in implementing QMRA. An adjusted framework for implementing QMRA for small water systems was formulated and discussed.

Cryptosporidium and Giardia in Wastewater and Surface Water Environments

and spp. are significant contributors to the global waterborne disease burden. Waterways used as sources of drinking water and for recreational activity can become contaminated through the introduction of fecal materials derived from humans and animals. Multiple studies have reported the occurence or concentrations of these pathogens in the environment. However, this information has not been comprehensively reviewed. Quantitative microbial risk assessment (QMRA) for and can be beneficial, but it often relies on the concentrations in environmental sources reported from the literature. A thorough literature review was conducted to develop an inventory of reported and concentrations in wastewater and surface water available in the literature. This information can be used to develop QMRA inputs. and (oo)cyst concentrations in untreated wastewater were up to 60,000 oocysts L and 100,000 cysts L, respectively. The maximum reported concentrations for and in surface water were 8400 oocysts L and 1000 cysts L, respectively. A summary of the factors for interpretation of concentration information including common quantification methods, survival and persistence, biofilm interactions, genotyping, and treatment removal is provided in this review. This information can help in identifying assumptions implicit in various QMRA parameters, thus providing the context and rationale to guide model formulation and application. Additionally, it can provide valuable information for water quality practitioners striving to meet the recreational water quality or treatment criteria. The goal is for the information provided in the current review to aid in developing source water protection and monitoring strategies that will minimize public health risks.

Changes in the incidence of intestinal giardiosis in Mexican population during five years (2011-2015)

Giardiosis is a parasitic disease caused by the protozoan Giardia intestinalis, which is distributed worldwide. Most of the data on the prevalence of giardiosis in Mexico comes from research, but it is also necessary to study the data provided by the Mexican Health Ministry and issued by the General Directorate of Epidemiology. The aim of this work was analyse the national surveillance data for human giardiosis in order to update the epidemiological data of this disease in Mexico. A retrospective observational analysis of giardiosis (from January 2011 to December 2015) was performed in the annual reports emitted by the GDE in Mexico. The cases were classified by year, state, age group, gender and seasons of the year. During the period of 2011-2015, a reduction of 38.51% was observed in the total number of new cases of giardiosis reported in the whole country The states of Sinaloa, Yucatan, and Chiapas presented the highest number of new cases reported during the analysed period. Giardiosis rates were always higher among women in all age groups, but the maximum incidence was observed in both sexes in the age group of 1-4 years old (the most susceptible group). On the other hand, the number of cases increased dramatically in southern states during warmer months. Giardiosis is influenced by ambient temperature changes along the year, although this study suggests that tends to decrease in all the analysed states and could be related to the overall improvement of hygienic practices within the Mexican population.

Estimating Cryptosporidium and Giardia disease burdens for children drinking untreated groundwater in a rural population in India

Background

In many low-income settings, despite improvements in sanitation and hygiene, groundwater sources used for drinking may be contaminated with enteric pathogens such as Cryptosporidium and Giardia, which remain important causes of childhood morbidity. In this study, we examined the contribution of diarrhea caused by Cryptosporidium and Giardia found in groundwater sources used for drinking to the total burden of diarrheal disease among children < 5 in rural India.

Methodology/Principal findings

We studied a population of 3,385 children < 5 years of age in 100 communities of Puri District, Odisha, India. We developed a coupled quantitative microbial risk assessment (QMRA) and susceptible-infected-recovered (SIR) population model based on observed levels of Cryptosporidium and Giardia in improved groundwater sources used for drinking and compared the QMRA-SIR estimates with independently measured all-cause (i.e., all fecal-oral enteric pathogens and exposure pathways) child diarrhea prevalence rates observed in the study population during two monsoon seasons (2012 and 2013). We used site specific and regional studies to inform assumptions about the human pathogenicity of the Cryptosporidium and Giardia species present in local groundwater. In all three human pathogenicity scenarios evaluated, the mean daily risk of Cryptosporidium or Giardia infection (0.06–1.53%), far exceeded the tolerable daily risk of infection from drinking water in the US (< 0.0001%). Depending on which protozoa species were present, median estimates of daily child diarrhea prevalence due to either Cryptosporidium or Giardia infection from drinking water was as high as 6.5% or as low as < 1% and accounted for at least 2.9% and as much as 65.8% of the all-cause diarrhea disease burden measured in children < 5 during the study period. Cryptosporidium tended to account for a greater share of estimated waterborne protozoa infections causing diarrhea than did Giardia. Diarrhea prevalence estimates for waterborne Cryptosporidium infection appeared to be most sensitive to assumptions about the probability of infection from ingesting a single parasite (i.e. the rate parameter in dose-response model), while Giardia infection was most sensitive to assumptions about the viability of parasites detected in groundwater samples.

Conclusions/Significance

Protozoa in groundwater drinking sources in rural India, even at low concentrations, especially for Cryptosporidium, may account for a significant portion of child diarrhea morbidity in settings were tubewells are used for drinking water and should be more systematically monitored. Preventing diarrheal disease burdens in Puri District and similar settings will benefit from ensuring water is microbiologically safe for consumption and consistent and effective household water treatment is practiced.

Water, sanitation, and hygiene (WASH) interventions aimed at reducing exposure to enteric pathogens have produced mixed health impacts, with some interventions finding no significant difference in health outcomes between intervention and control groups. While there are many explanations why individual WASH interventions may not achieve improved health outcomes, one reason is an incomplete understanding of the conditions that favor perpetuation and transmission of enteric pathogens in a given population and region. In this study, we developed a set of diarrhea-causing disease transmission models using measurements of drinking water contamination and child diarrhea over the same time period in the same study population. Using the disease transmission models, we examined how much of the observed diarrhea in children was due to waterborne transmission of enteric pathogens in a program in rural India that improved household sanitation but failed to produce improvements in child health. We focused on the role of two enteric protozoal pathogens, Cryptosporidium and Giardia, and diarrhea rates among children < 5 years of age in these communities. We found that Cryptosporidium and Giardia infections from drinking water contaminated with these enteric protozoa may have together caused as much as 65.8% (IQR 63.4–68.2%) or as little as 2.9% (IQR 2.3–3.4%) of the observed diarrhea in children depending on modeling assumptions about which protozoa species were present. These findings suggest implementing a single barrier, such as only sanitation, to disrupt the multiple pathways of fecal-oral transmission of enteric pathogens, rather than multiple barriers, such as sanitation and safe drinking water, may lead some interventions to fall short of achieving measurable health improvements. Finally, our research suggests that Cryptosporidium and Giardia may cause significant amounts of child diarrhea morbidity even at low levels of concentration when present in improved drinking water sources and their measurement should be including in community drinking water quality monitoring programs.

Prevalence of protozoa species in drinking and environmental water sources in Sudan

Protozoa are eukaryotic cells distributed worldwide in nature and are receiving increasing attention as reservoirs and potential vectors for the transmission of pathogenic bacteria. In the environment, on the other hand, many genera of the protozoa are human and animal pathogens. Only limited information is available on these organisms in developing countries and so far no information on their presence is available from Sudan. It is necessary to establish a molecular identification of species of the protozoa from drinking and environmental water. 600 water samples were collected from five states (Gadarif, Khartoum, Kordofan, Juba, and Wad Madani) in Sudan and analysed by polymerase chain reaction (PCR) and sequencing. 57 out of 600 water samples were PCR positive for protozoa. 38 out of the 57 positive samples were identified by sequencing to contain 66 protozoa species including 19 (28.8%) amoebae, 17 (25.7%) Apicomplexa, 25 (37.9%) ciliates, and 5 (7.6%) flagellates. This study utilized molecular methods identified species belonging to all phyla of protozoa and presented a fast and accurate molecular detection and identification of pathogenic as well as free-living protozoa in water uncovering hazards facing public health.