Is there any change in the prevalence of intestinal or cardiopulmonary parasite infections in companion animals (dogs and cats) in Germany between 2004-2006 and 2015-2017? An assessment of the impact of the first ESCCAP guidelines.

Main objective of the present nationwide study was to assess the impact of the ESCCAP guideline for the control of worm infections in dogs and cats 8-10 years after its first publication in Germany. A secondary aim was to determine the prevalence of canine and feline cardiopulmonary nematodes and intestinal protozoa. Faecal samples of 53,693 dogs and 26,491 cats in 2004-2006 as well as of 129,578 dogs and 45,709 cats in 2015-2017 routinely submitted by veterinarians to a private veterinary laboratory were examined using appropriate parasitological methods. In dogs, the prevalence of Toxocara and taeniid egg shedding was significantly lower in 2015-2017 (3.8 % and 0.16 %, respectively) than in 2004-2006 (4.6 % and 0.27 %, respectively). The prevalence of hookworm and Capillaria eggs was higher in the second study period (2.3 % and 0.77 %, respectively) than in the first (1.3 % and 0.6 %, respectively). For Toxascaris leonina (0.55-0.6 %) and Trichuris (0.8-0.9 %), the difference was not significant between the study periods. Dogs shed more often Angiostrongylus vasorum larvae in the second study (3.1 %) than in the first (1.0 %), whereas the prevalence of Crenosoma vulpis did not change significantly (2.2-2.6 %). Cystoisospora canis and C. ohioensis-like infections were less detected in the second study period (1.0 % and 2.1 %, respectively) than in the first (1.8 % and 2.7 %, respectively). Neospora-like oocysts and Sarcocystis sporocysts were more prevalent in the second study period (0.19 % and 0.13 %, respectively) than in the first (0.13 % and 0.06 %, respectively). The percentage of Giardia or Cryptosporidium coproantigen-positive samples was lower in the second study period (18.9 % and 6.7 %, respectively) than in the first (22.8 % and 10.0 %, respectively). In cats, the prevalence of egg shedding of T. cati, Capillaria and taeniids was significantly lower in 2015-2017 (3.5 %, 0.25 % and 0.1 %, respectively) than in 2004-2006 (4.8 %, 0.54 % and 0.22 %, respectively). No difference was recorded for hookworms (0.12-0.13 %) and Ts. leonina (0.04-0.05 %). Aelurostrongylus-like larvae were detected more often in the second study period (6.5 %) than in the first (2.6 %). Infections with Cystoisospora felis, C. rivolta, Toxoplasma-like coccids and Sarcocystis were less prevalent in the second study period (1.9 %, 0.7 %, 0.24 % and 0.02 %, respectively) than in the first (2.7 %, 1.1 %, 0.36 % and 0.1 %, respectively). The percentage of Giardia or Cryptosporidium coproantigen-positive samples was significantly lower in the second study period (10.6 % and 4.8 %, respectively) than in the first (15.4 % and 8.3 %, respectively). Although these results indicate a decline of the occurrence of most canine and feline intestinal parasites in Germany over the years, a transmission risk of zoonotic parasites remains. Therefore, the control of helminth infections in domestic dogs and cats continues to be a challenge for veterinarians and pet owners.

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.

Importance of Distributional Forms for the Assessment of Protozoan Pathogens Concentrations in Drinking-Water Sources.

The identification of appropriately conservative statistical distributions is needed to predict microbial peak events in drinking water sources explicitly. In this study, Poisson and mixed Poisson distributions with different upper tail behaviors were used for modeling source water Cryptosporidium and Giardia data from 30 drinking water treatment plants. Small differences (<0.5-log) were found between the "best" estimates of the mean Cryptosporidium and Giardia concentrations with the Poisson-gamma and Poisson-log-normal models. However, the upper bound of the 95% credibility interval on the mean Cryptosporidium concentrations of the Poisson-log-normal model was considerably higher (>0.5-log) than that of the Poisson-gamma model at four sites. The improper choice of a model may, therefore, mislead the assessment of treatment requirements and health risks associated with the water supply. Discrimination between models using the marginal deviance information criterion (mDIC) was unachievable because differences in upper tail behaviors were not well characterized with available data sets ( n<30 ). Therefore, the gamma and the log-normal distributions fit the data equally well but may predict different risk estimates when they are used as an input distribution in an exposure assessment. The collection of event-based monitoring data and the modeling of larger routine monitoring data sets are recommended to identify appropriately conservative distributions to predict microbial peak events.

Waterborne protozoan pathogens in environmental aquatic biofilms: Implications for water quality assessment strategies.

Biofilms containing pathogenic organisms from the water supply are a potential source of protozoan parasite outbreaks and a significant public health concern. The aim of the present study was to demonstrate the simultaneous and multi-spatial occurrence of waterborne protozoan pathogens (WBPP) in substrate-associated biofilms (SAB) and compare it to surface water (SW) and sediments with bottom water (BW) counterparts using manual filtration and elution from low-volume samples. For scenario purposes, simulated environmental biofilm contamination was created from in-situ grown one-month-old SAB (OM-SAB) that were spiked with Cryptosporidium parvum oocysts. Samples were collected from the largest freshwater reservoirs in Luzon, Philippines and a University Lake in Thailand. A total of 69 samples (23 SAB, 23 SW, and 23 BW) were evaluated using traditional staining techniques for Cryptosporidium, and Immunofluorescence staining for the simultaneous detection of Cryptosporidium and Giardia. WBPP were found in 43% SAB, 39% SW, and 39% BW of the samples tested in the present study with SAB results reflecting SW and BW results. Further highlights were demonstrated in the potential of using low-volume samples for the detection of parasites in source water. Scanning electron microscopy of OM-SAB samples revealed a naturally-associated testate amoeba shell, while Cryptosporidium oocysts spiked samples provided a visual profile of what can be expected from naturally contaminated biofilms. This study provides the first evidence for the simultaneous and multi-spatial occurrence of waterborne protozoan pathogens in low-volume aquatic matrices and further warrants SAB testing along with SW and BW matrices for improved water quality assessment strategies (iWQAS).

Cryptosporidium and Giardia in Africa: current and future challenges.

Cryptosporidium and Giardia are important causes of diarrhoeal illness. Adequate knowledge of the molecular diversity and geographical distribution of these parasites and the environmental and climatic variables that influence their prevalence is important for effective control of infection in at-risk populations, yet relatively little is known about the epidemiology of these parasites in Africa. Cryptosporidium is associated with moderate to severe diarrhoea and increased mortality in African countries and both parasites negatively affect child growth and development. Malnutrition and HIV status are also important contributors to the prevalence of Cryptosporidium and Giardia in African countries. Molecular typing of both parasites in humans, domestic animals and wildlife to date indicates a complex picture of both anthroponotic, zoonotic and spill-back transmission cycles that requires further investigation. For Cryptosporidium, the only available drug (nitazoxanide) is ineffective in HIV and malnourished individuals and therefore more effective drugs are a high priority. Several classes of drugs with good efficacy exist for Giardia, but dosing regimens are suboptimal and emerging resistance threatens clinical utility. Climate change and population growth are also predicted to increase both malnutrition and the prevalence of these parasites in water sources. Dedicated and co-ordinated commitments from African governments involving "One Health" initiatives with multidisciplinary teams of veterinarians, medical workers, relevant government authorities, and public health specialists working together are essential to control and prevent the burden of disease caused by these parasites.

Epidemiology of Cryptosporidium infection in cattle in China: a review.

The present review discusses the findings of cryptosporidiosis research conducted in cattle in China and highlights the currently available information on Cryptosporidium epidemiology, genetic diversity, and distribution in China, which is critical to understanding the economic and public health importance of cryptosporidiosis transmission in cattle. To date, 10 Cryptosporidium species have been detected in cattle in China, with an overall infection rate of 11.9%. The highest rate of infection (19.5%) was observed in preweaned calves, followed by that in juveniles (10.69%), postweaned juveniles (9.0%), and adult cattle (4.94%). The dominant species were C. parvum in preweaned calves and C. andersoni in postweaned, juvenile, and adult cattle. Zoonotic Cryptosporidium species (C. parvum and C. hominis) were found in cattle, indicating the possibility of transmission between humans and cattle. Different cattle breeds had significant differences in the prevalence rate and species of Cryptosporidium. This review demonstrates an age-associated, breed-associated, and geographic-related occurrence of Cryptosporidium and provides references for further understanding of the epidemiological characteristics, and for preventing and controlling the disease.

[Establishment of a risk assessment model for laboratory biosafety of Cryptosporidium].

OBJECTIVE: To evaluate the risk assessment model of Cryptosporidium laboratory, so as to provide the basis for laboratory personnel engaging in the operation of Cryptosporidium. METHODS: Firstly, the risk factors of Cryptosporidium infection in laboratory were determined by the literature and Delphi, and then the weights of risk factors were determined by fuzzy analytic hierarchy process. A risk assessment model for laboratory biosafety of Cryptosporidium was established. RESULTS: Compared to the indexes, based on the risk assessment model, stool sample processing was the two steps in the laboratory with high risk of infection and high risk factors, with the combination weights of risk possibility and hazard rating were 0.111 and 0.107, respectively. CONCLUSIONS: The risk assessment model established is feasible. It can be used to make some suggestions for the related laboratory staff.

Local health department food safety and sanitation expenditures and reductions in enteric disease, 2000-2010.

OBJECTIVES: In collaboration with Public Health Practice-Based Research Networks, we investigated relationships between local health department (LHD) food safety and sanitation expenditures and reported enteric disease rates. METHODS: We combined annual infection rates for the common notifiable enteric diseases with uniquely detailed, LHD-level food safety and sanitation annual expenditure data obtained from Washington and New York state health departments. We used a multivariate panel time-series design to examine ecologic relationships between 2000-2010 local food safety and sanitation expenditures and enteric diseases. Our study population consisted of 72 LHDs (mostly serving county-level jurisdictions) in Washington and New York. RESULTS: While controlling for other factors, we found significant associations between higher LHD food and sanitation spending and a lower incidence of salmonellosis in Washington and a lower incidence of cryptosporidiosis in New York. CONCLUSIONS: Local public health expenditures on food and sanitation services are important because of their association with certain health indicators. Our study supports the need for program-specific LHD service-related data to measure the cost, performance, and outcomes of prevention efforts to inform practice and policymaking.

Burden of childhood diseases and malnutrition in a semi-urban slum in southern India.

BACKGROUND: India has seen rapid unorganized urbanization in the past few decades. However, the burden of childhood diseases and malnutrition in such populations is difficult to quantify. The morbidity experience of children living in semi-urban slums of a southern Indian city is described. METHODS: A total of 176 children were recruited pre-weaning from four geographically adjacent, semi-urban slums located in the western outskirts of Vellore, Tamil Nadu for a study on water safety and enteric infections and received either bottled or municipal drinking water based on their area of residence. Children were visited weekly at home and had anthropometry measured monthly until their second birthday. RESULTS: A total of 3932 episodes of illness were recorded during the follow-up period, resulting in an incidence of 12.5 illnesses/child-year, with more illness during infancy than in the second year of life. Respiratory, mostly upper respiratory infections, and gastrointestinal illnesses were most common. Approximately one-third of children were stunted at two years of age, and two-thirds had at least one episode of growth failure during the two years of follow up. No differences in morbidity were seen between children who received bottled and municipal water. CONCLUSIONS: Our study found a high burden of childhood diseases and malnutrition among urban slum dwellers in southern India. Frequent illnesses may adversely impact children's health and development, besides placing an additional burden on families who need to seek healthcare and find resources to manage illness.

Assessing the infection risk of Giardia and Cryptosporidium in public drinking water delivered by surface water systems in Sao Paulo State, Brazil.

A survey of Giardia and Cryptosporidium was conducted in surface water used as drinking water sources by public water systems in four densely urbanized regions of Sao Paulo State, Brazil. A Quantitative Microbial Risk Assessment, based on protozoa concentrations, was performed to estimate the probability of protozoa infection associated with drinking water ingestion. A total of 206 source water samples were analyzed over a 24 month period using the USEPA Method 1623. The risk of infection was estimated using an exponential dose response model, children and adults exposure and a gamma distribution for (oo)cyst concentrations with three scenarios for treating censored data. Giardia was detected in 102 of the samples, and 19 of them were also positive for Cryptosporidium, with maximum concentrations of 97.0 cysts/L and 6.0 oocysts/L, respectively. Risk distributions were similar for the three scenarios. In the four regions, the estimated risk of Giardia infection per year, for adults and children, ranged from 0.29% to 2.47% and from 0.08% to 0.70%, respectively. Cryptosporidium risk infection varied from 0.15% to 0.29% for adults and from 0.04% to 0.08% for children. In both cases, the calculated risk surpassed the risk of infection of 10(-4) (1:10,000) defined as tolerable by USEPA for a yearly exposure. The probability of Giardia infection was very close to the rates of acute diarrheic disease for adults (1% to 3%) but lower for children (2% to 7%). The daily consumption of drinking water was an important contributing factor for these differences. The Microbiological Risk Assessment carried out in this study provides an indication of infection risks by Giardia and Cryptosporidium in the population served by these source waters. Strategies for source water protection and performance targets for the water treatment should be established to achieve the required level of public health risk.

Burden of disease from cryptosporidiosis.

PURPOSE OF REVIEW: The global significance of cryptosporidiosis is widespread and far-reaching. In this review, we present recent data about strain diversity and the burden of disease, along with developments in therapeutic and preventive strategies. RECENT FINDINGS: Cryptosporidium is an emerging pathogen that disproportionately affects children in developing countries and immunocompromised individuals. Without a diagnostic tool amenable for use in developing countries, the burden of infection and its relationship to growth faltering, malnutrition, and diarrheal mortality remain underappreciated. Disease incidence is also increasing in industrialized countries largely as a result of outbreaks in recreational water facilities. Advances in molecular methods, including subtyping analysis, have yielded new insights into the epidemiology of cryptosporidiosis. However, without practical point-of-care diagnostics, an effective treatment for immunocompromised patients, and a promising vaccine candidate, the ability to reduce the burden of disease in the near future is limited. This is compounded by inadequate coverage with antiretroviral therapy in developing countries, the only current means of managing HIV-infected patients with cryptosporidiosis. SUMMARY: Cryptosporidiosis is one of the most important diarrheal pathogens affecting people worldwide. Effective methods to control and treat cryptosporidiosis among high-risk groups present an ongoing problem in need of attention.

Promotion of healthy swimming after a statewide outbreak of cryptosporidiosis associated with recreational water venues--Utah, 2008-2009.

During the summer of 2007, Utah experienced a statewide outbreak of gastrointestinal illness caused by Cryptosporidium, a parasite transmitted via the fecal-oral route. Approximately 5,700 outbreak-related cases were identified across the state. Of 1,506 interviewed patients with laboratory-confirmed cryptosporidiosis, 1,209 (80%) reported swimming in at least one of approximately 450 recreational water venues during their potential 14-day incubation period. Cryptosporidium is extremely chlorine-tolerant, and secondary or supplemental disinfection with ultraviolet light or ozone can control but not prevent outbreaks. Because swimmers are the primary source of Cryptosporidium contamination, healthy swimming campaigns are needed to increase awareness and practice of healthy swimming behaviors, especially not swimming while ill with diarrhea (i.e., swimming while ill with diarrhea can lead to gross contamination of recreational water). Before the 2008 summer swimming season, Utah public health agencies launched a multimedia healthy swimming campaign. To assess knowledge of healthy swimming, a survey of Utah residents was conducted during July-September 2008. The results of that survey found that 96.1% of respondents correctly indicated that "it is not OK to swim if you have diarrhea." In a separate national survey in 2009, 100% of Utah residents but only 78.4% of residents of other states correctly indicated that "not swimming while ill with diarrhea protects others from recreational water illnesses (RWIs)." No recreational water-associated outbreaks were detected in Utah during 2008-2011. The healthy swimming campaign, as part of a multipronged prevention effort, might have helped prevent recreational water-associated outbreaks of cryptosporidiosis in Utah.

Policy, practice and decision making for zoonotic disease management: water and Cryptosporidium.

Decision making for zoonotic disease management should be based on many forms of appropriate data and sources of evidence. However, the criteria and timing for policy response and the resulting management decisions are often altered when a disease outbreak occurs and captures full media attention. In the case of waterborne disease, such as the robust protozoa, Cryptosporidium spp, exposure can cause significant human health risks and preventing exposure by maintaining high standards of biological and chemical water quality remains a priority for water companies in the UK. Little has been documented on how knowledge and information is translated between the many stakeholders involved in the management of Cryptosporidium, which is surprising given the different drivers that have shaped management decisions. Such information, coupled with the uncertainties that surround these data is essential for improving future management strategies that minimise disease outbreaks. Here, we examine the interplay between scientific information, the media, and emergent government and company policies to examine these issues using qualitative and quantitative data relating to Cryptosporidium management decisions by a water company in the North West of England. Our results show that political and media influences are powerful drivers of management decisions if fuelled by high profile outbreaks. Furthermore, the strength of the scientific evidence is often constrained by uncertainties in the data, and in the way knowledge is translated between policy levels during established risk management procedures. In particular, under or over-estimating risk during risk assessment procedures together with uncertainty regarding risk factors within the wider environment, was found to restrict the knowledge-base for decision-making in Cryptosporidium management. Our findings highlight some key current and future challenges facing the management of such diseases that are widely applicable to other risk management situations.

Water reclamation redesign for reducing Cryptosporidium risks at a recreational spray park using stochastic models.

Recreational outbreaks associated with sprayparks are well recognized, and may be partly due to the engineering designs used for their water reclamation systems are problematic to control. This work is based on an outbreak of cryptosporidiosis linked to a spraypark in New York State, where it was determined, specifically that the spraypad (the main attraction) was the primary exposure point. We first determined the likely dose the spraypad users were exposed to, then modeled the efficacy of the treatment system and used this to inform a Monte Carlo method to estimate the probability of infection and illness for the users of the spraypad. The current treatment system which consists of; two holding tanks, a dual media filter and chlorine injection as well as two design change recommendations were modeled using three independent Markov chain models. Within the current treatment system design the receiving tank for the treatment train is also connected with a second pipe to the spraypad used to deliver the return (treated) water, this return pipe is acting potentially as a bypass for the treatment train. Based on the risk assessments performed it is recommended that the bypass pipe be removed from the treatment system since in doing so the probability of infection and illness were reduced appreciably. Secondarily including an ozone contactor was shown to slightly reduce the risk further and provide a multiple barrier.

Prevalence of and management factors contributing to Cryptosporidium sp. infection in pre-weaned and post-weaned calves in Johor, Malaysia.

A cross-sectional study was carried out to identify species and determine the prevalence of Cryptosporidium sp. shedding in pre-weaned and post-weaned dairy calves and to identify management factors that may be contributing to disease. A total of 240 calf faecal samples were collected from 16 farms in two districts in Johor, Malaysia, and screened by PCR. The overall Cryptosporidium prevalence was 27.1%. The prevalence of Cryptosporidium species in pre-weaned calves was 32.4% for C. parvum, 26.5% for C. bovis, followed by C. andersoni (20.6%), C. ryanae (11.8%) and mixed sp. (8.8%). The prevalence of Cryptosporidium species in post-weaned calves was 35% for C. bovis followed by C. andersoni and C. ryanae (30% each) and mixed sp. (5%). Subtyping analysis of 8 of the 11 C. parvum isolates at the gp60 locus identified five isolates as IIdA15G1, one as IIa18A3R1 and two isolates as IIa17G2R1. Management factors that increased the risk of Cryptosporidium infection included having other cattle farms close by, feeding calves with saleable milk, keeping pre-weaned calves in pens with slatted floors and keeping post-weaned calves in pens with a sand floor.

[Cryptosporidiosis: an emerging zoonosis]. / Criptosporidiosis: una zoonosis emergente.

The genus Cryptosporidium, responsible for producing cryptosporidiosis, includes several species. Humans and livestock are the main sources of infection. Waterborne cryptosporidiosis outbreaks are associated with drinking water. The infective parasite stage is the oocyst, which is resistant to conventional potabilization treatments. In immunocompetent hosts it produces acute, self-limiting diarrhoea. In immunocompromised people, it could develop severe, life-threatening pattern forms of the infection. People with AIDS are especially susceptible to these clinical forms. Cryptosporidium infections are also considered a major cause of morbimortality in calves, which leads to important economic losses. In the last years, there has been an increase of patients suffering from different causes of immunosuppression, and the need to find an effective therapy against Cryptosporidium has become greater. In spite of the many attempts of the pharmaceutical industry to develop an effective antiparasitic agent to treat cryptosporidiosis, this infection and its clinical consequences still constitute a major public health problem. This article analizes the taxonomy, morphology, biology and life cycle of Cryptosporidium. Clinical, immunological, epidemiological features and diagnosis of cryptosporidiosis are also included. Treatment and prevention of the infection are discussed, and future tendencies are suggested for this emerging parasitic infection.

Molecular characterisation of species and genotypes of Cryptosporidium and Giardia and assessment of zoonotic transmission.

The molecular characterisation of species and genotypes of Cryptosporidium and Giardia is essential for accurately identifying organisms and assessing zoonotic transmission. Results of recent molecular epidemiological studies strongly suggest that zoonotic transmission plays an important role in cryptosporidiosis epidemiology. In such cases the most prevalent zoonotic species is Cryptosporidium parvum. Genotyping and subtyping data suggest that zoonotic transmission is not as prevalent in the epidemiology of giardiasis. Molecular characterisation of Cryptosporidium and Giardia is a relatively recent application that is evolving as new genes are found that increase the accuracy of identification while discovering a greater diversity of species and yet unnamed taxa within these two important genera. As molecular data accumulate, our understanding of the role of zoonotic transmission in epidemiology and clinical manifestations is becoming clearer.

The Milwaukee Cryptosporidium outbreak: assessment of incubation time and daily attack rate.

The time course of reported illnesses (epidemic curve) in the 1993 Milwaukee outbreak of cryptosporidiosis was analysed using a dynamic model considering time variant force of infection and incubation time distributions. Different functional forms for the force of infection and incubation time distribution were tested. The resulting model is a coupled integro-differential equation system. These models gave a good fit to the data, although depending upon the functional forms of the underlying distributions, different incubation time and force of infection curves were obtained. However there was reasonable agreement with respect to a baseline illness rate that existed. This demonstrates that useful information may be obtained in this manner, although it should be supplemented with other data (e.g. serology) for a precise assessment of dynamics of disease occurrence during waterborne epidemic conditions.

Uncertainties in risk assessment for the determination of drinking water pollutant concentrations: Cryptosporidium case study.

There is a growing acknowledgement of the need to recognise uncertainties in the estimation of waterborne risks. In this paper, the strength of the science available to characterise Cryptosporidium risks in drinking water is investigated, in particular the determination of oocyst concentrations at various points in the chain of water supply. A recently developed scientific quality audit framework is used as a tool to guide this investigation. The framework systematically reveals the relatively greater strength of the science for the "upstream" elements (estimation of concentrations in environmental reservoirs) than for the "downstream" elements (concentrations in distribution). It is the downstream elements that have greater bearing on human health and public policy issues. It is noted that the adoption of new monitoring Regulations is likely to prompt action to strengthen knowledge of these downstream elements in the future.

Balancing the risks and benefits of drinking water disinfection: disability adjusted life-years on the scale.

To evaluate the applicability of disability adjusted life-years (DALYs) as a measure to compare positive and negative health effects of drinking water disinfection, we conducted a case study involving a hypothetical drinking water supply from surface water. This drinking water supply is typical in The Netherlands. We compared the reduction of the risk of infection with Cryptosporidium parvum by ozonation of water to the concomitant increase in risk of renal cell cancer arising from the production of bromate. We applied clinical, epidemiologic, and toxicologic data on morbidity and mortality to calculate the net health benefit in DALYs. We estimated the median risk of infection with C. parvum as 10(-3)/person-year. Ozonation reduces the median risk in the baseline approximately 7-fold, but bromate is produced in a concentration above current guideline levels. However, the health benefits of preventing gastroenteritis in the general population and premature death in patients with acquired immunodeficiency syndrome outweigh health losses by premature death from renal cell cancer by a factor of > 10. The net benefit is approximately 1 DALY/million person-years. The application of DALYs in principle allows us to more explicitly compare the public health risks and benefits of different management options. In practice, the application of DALYs may be hampered by the substantial degree of uncertainty, as is typical for risk assessment.