Appendix A8
Summary of research documents on Cryptosporidium abstracted between 1995 and 1998 1
A8.1 Introduction
A8.1.1 This Appendix contains a summary of research papers on Cryptosporidium and Giardia which have been published worldwide between the beginning of 1995 and the present date. The papers have been summarised in broad subject areas and the full references are given after the text. This summary is reproduced here for information only, the Expert Group does not necessarily endorse the work or findings.
A8.1.2 A portion of the work is centred around water treatment, in particular the optimisation of existing coagulation and flocculation practices. Novel treatments such as ultra-filtration and nano-filtration also appear. Disinfection studies have looked at combinations of disinfectants to obtain synergistic effects and the application of new technologies such as mixed oxidant species and ultra-violet light (UV). A variety of viability assays are available, from mouse infectivity, tissue culture, excystation and dye exclusion. Of all of these perhaps tissue culture may be a valuable technique for the future.
A8.1.3 Waterborne outbreaks of cryptosporidiosis have been reported from around the world associated with the consumption of contaminated drinking water or the ingestion of contaminated recreational waters. The reports indicated that outbreaks have been associated with filtered and unfiltered surface waters, groundwaters and contaminated distribution systems. A number of outbreaks have involved swimming pools, usually after faecal contamination of the water. Distributions of cysts and oocysts in surface waters, groundwaters, sewage effluents and slurries have been studied, and in particular efforts have been made to collect data other than through routine sampling programmes. It is not always possible to know when oocysts are present in high numbers, but efforts should be made to collect data when environmental conditions suggest deterioration of raw water quality. In addition a clear understanding of the likely input of parasites to a raw water catchment is helpful.
A8.1.4 Methods for detection continue to improve. Many authors highlight the need to understand recovery efficiencies and the factors that can lead to poor recoveries. Perhaps collation of this data might be useful as a How to improve your analysis' guide. Emphasis for the most part is on simplicity with reproducibility and the need for quality control. There are many variables in any detection method and it is important that a laboratory knows what these are. Better concentration techniques, the use of immunomagnetic separation (IMS) and flow cytometry have all helped to improve detection and reduce analytical time. Determination of viability by tissue culture is an interesting development. The viability of a single oocyst can be determined from replication of sporozoites. Detection may be by means of enzyme-linked immunosorbent assay (ELISA) or using molecular techniques, with viability assay times ranging from 24 to 48 hours. Molecular techniques are based on either DNA or RNA amplification, or fluorescent in situ hybridisation (FISH). These techniques also demonstrate potential viability and infectivity. The Standing Committee of Analysts and the United States Environment Protection Agency both have draft revised methods for the analysis of water samples. The rate of progress with development will probably mean that they will be out of date before too long.
A8.1.5 Studies of survival in the environment continue to demonstrate that whilst Giardia is a poor survivor, Cryptosporidium can survive well, although aged oocysts are more susceptible to environmental factors and the effects of disinfectants.
This summary was prepared for the Expert Group by AlControl and WRc plc under contract to the Drinking Water Inspectorate.
A8.2 Sampling
A8.2.1 Walker et al. (1997) have described a sampling device, operating under a gravity head, for sampling streams during periods of moderated sediment-generated turbidity.
A8.3 Detection
A8.3.1 Shepherd and Wyn-Jones (1996) compared membrane filtration (142-mm) with flocculation and cartridge filtration for recovering Giardia and Cryptosporidium from tap and river water. Flocculation gave the best recoveries of both parasites from both water types. A 1.2µm cellulose acetate membrane was found to be best for Cryptosporidium and a 3.0µm cellulose nitrate membrane best for Giardia . Ongerth (1997) evaluated membrane filtration, cartridge filtration and chemical flocculation for the recovery of Giardia and Cryptosporidium from seeded river, reservoir and tap water samples. Chemical flocculation and membrane filtration gave comparable results whilst cartridge filtration gave poor recoveries. Investigation of losses during sample processing are discussed by Grimason et al. (1997). Highest losses occur during filtration with wound yarn cartridges (up to 36% pass through) and flotation (up to 41%). Filter elution and centrifugation also create losses. A coefficient of variance of up to 40% can be observed.
A8.3.2 Clancy et al (1997a) have compared two types of membrane filter, a stainless steel cartridge filter, a polysulphone cartridge filter and vortex flow filtration for recovering oocysts from 10-litre volumes of seeded tap water. Fricker et al. (1997b) describe the use of vortex flow filtration which can achieve >90% recovery, together with Immunomagnetic Separation (IMS) which can give similar recoveries, as a rapid and reliable detection system for Giardia and Cryptosporidium in water. Vortex filtration, Nuclepore filters (ongoing) and Envirocheck filters (Gelman) were examined by Matheson et al. (1997) as alternatives to flocculation and flat bed membrane filtration. Recoveries for each of the membranes was >50% for both parasites and gave significantly less variation than wound fibre cartridges.
A8.3.3 Clancy et al. (1997b) describe trials in the USA and the UK using filtration with either vortex flow, Gelman Envirocheck, capsule filters or Costar 5-inch filters. The filters gave >70- 96% recovery. Samples were further concentrated by IMS and could be stained with monoclonal antibody and DAPI/PI. Parton et al. (1997) describe an open cell reticulated foam filter which can concentrate oocysts from water with an efficiency of >95%. Samples are recovered in 5-10 minutes in volumes of 250 ml and the process requires minimum equipment and operator skill. Monro (1998) described a filter that achieved enhanced recovery of Cryptosporidium oocysts. It consisted of discs of foam compressed into a small cylinder. It is estimated that a recovery of at least 80% of oocysts could be achieved, and up to 2000 litres of water could be passed through the unit without clogging or breakthrough. An immuno-affinity separator, selective for Cryptosporidium, is being developed. Johnson et al. (1995) compared two methods for concentrating parasites from 300-litre seeded samples of marine waters. The Filterite negatively-charged filter was found to be simpler and faster, with reduced interference from algae, than the wound polypropylene cartridge.
A8.3.4 New approaches to detection are described by Whitmore (1997), including hydrocyclones, magnetically stabilised fluidised beds, dynamic membranes and flow cytometry using two-colour sorting. Graczyk et. al. (1997a) outline the importance of using an eluting fluid for recovery of residual oocysts from sample containers. Trials showed a mean of 34.7% retention in sample containers and recoveries increased from 44.1% without elution to nearly 78%. They also demonstrated (Graczyk et al. 1997b) that dissolution of cellulose acetate membranes with acetone and parasite concentration using ethanol does not affect stain intensity with monoclonal antibodies or infectivity in BALB/c mice.
A8.3.5 Campbell and Smith (1997) describe an inter-laboratory trial using IMS for the concentration of Cryptosporidium from seeded water samples. With low turbidity waters, IMS was found to be better than microscopy and flow cytometry. With increased turbidity, the efficiency of IMS diminished. Campbell et al (1997b) describe an improved immunomagnetic procedure for concentrating Cryptosporidium from high turbidity samples. Selective concentration of oocysts was achieved from waters with turbidities ranging from 60 to 6,000 NTU and for a wide range of different water types.
A8.3.6 In a recent study comparing counting methods, Klonicki et al. (1997) found that there were significant variations between haemocytometer, cellulose acetate and well-slide counting. Recovery after cleaning with percoll/sucrose also varied. Hoffmann et al. (1997) discussed the use of flow cytometry compared with direct microscopy for the detection of Giardia and Cryptosporidium in water samples. Flow cytometry was found to take less time, cost less, and could analyse a greater volume of sample. An increase in sensitivity of almost three times was observed for both parasites. A review of flow cytometry has been published by Deere et al. (1996). Medema (1997a) describes the detection of Cryptosporidium and Giardia in river and reservoir water using flow cytometry. Viability was demonstrated by DAPI/PI staining before sorting and could easily be assessed. A number of oocysts were observed to be DAPI and PI negative but internal contents could not be resolved.
A8.3.7 Deere et al, (1997) discuss the use of two antibodies specific for Cryptosporidium labelled with different coloured fluorochromes to minimise non-specific sorting in flow cytometry together with a specific DNA probe to identify at genus or sub-species level and demonstrate viability. Vesey et al. (1997) describe the development of an IgG1 monoclonal antibody which is less sticky and reduces the amount of non-specific binding. This helps microscopy and sorting with a flow cytometer. The authors also provide some guidance on how to evaluate antibodies and improve existing reagents. A flow-cytometric assay was developed by Vesey et al.(1997) to evaluate Cryptosporidium-specific antibodies for testing water samples. There were significant differences in performance between the five different monoclonal antibodies used in the study.
A8.3.8 Rodgers et al. (1995) tested 54 algal species and found that 24 showed some fluorescence. Two species showed bright green fluorescence. Blocking with goat serum was found to be successful. Dowd and Pillai (1997) describe the use of propidium iodide with immunofluorescence to detect oocysts and determine viability. Three different inactivation methods were used in the study.
A8.3.9 Clancy (1997a) reports that in studies, laboratories produce highly variable data, and in some trials cannot detect seeds as high as 4,000 oocysts, and may therefore not detect oocysts in an outbreak. Health officials may misuse data particularly when advising AIDS patients about risk. Smith and Fricker (1997) discuss the variabilities that current analytical techniques have. They provide data on a range of analytical techniques, from filtration to drying on a slide, which can enable analysts to optimise some of their methodology and improve recoveries. Fricker et al . (1997a) discuss some factors which can produce variations in assessing the recovery efficiency of various analytical methods. Spikes should be counted in replicates of 10 and the whole recovered pellet examined. The source, age and condition of oocysts will have an effect as will the time that the oocysts have been in water. Where laboratories are comparing methods they should use the same type of water. Veal et al. (1997) describe rigorous quality control procedures for Cryptosporidium and Giardia analysis where one sample in ten is seeded for recovery. The information allows optimisation of different stages of analysis, comparison of recoveries from different water types and modification of results to present values corrected for recovery.
A8.3.10 Sartory (1997) was unable to find any relationship between sulphite-reducing clostridia, enterococci and the presence of Cryptosporidium in surface and groundwater in samples taken for routine analysis over a two year period.
A8.4 Molecular techniques
A8.4.1 Mayer and Palmer (1996) used immunofluorescence, PCR and nested PCR to investigate the removal of Giardia and Cryptosporidium from wastewater. Immunofluorescence demonstrated a 3-log reduction for Giardia and a 2-log reduction for Cryptosporidium. PCR gave 100% correlation for Giardia but slightly less for Cryptosporidium. Stinear et al. (1996) describe an RT-PCR technique capable of detecting a single oocyst in reticulated, reservoir, borehole and river water. No product was obtained in oocysts fixed with formalin. Cryptosporidium parvum was grown in Caco-2 cells by Rochelle et al. (1997b). PCR was used to detect the heat-shock protein 70. A single infectious oocyst could be detected using this procedure. Additional data is given on in vitro infectivity with in situ PCR and probe hybridisation for the specific quantification of infectious Cryptosporidium parvum in water (Rochelle et al. 1997b). A comparative evaluation of different polymerase chain reaction (PCR) primers was undertaken by Sluter et al. (1997), using several published protocols, with the aim of optimising PCR detection of low concentrations of Cryptosporidium parvum oocysts in raw and finished water.
A8.4.2 Battigelli (1997) describes an integrated ELISA/RT-PCR tissue culture procedure using human adenocarcinoma (HCT-8) cells. ELISA could assess viability down to 20 oocysts and RT-PCR could reduce this to one oocyst. A simple membrane filter procedure is described by Wiedenmann et al. (1997) whereby filtered oocysts are stained and counted, the membrane is dissolved in acetone and excystation of sporozoites is followed by PCR. The PCR can currently detect 10-20 viable oocysts but sensitivity is expected to increase. Recent research on DNA electrochemical sensors for a number of pathogens, including the use of an oligonucleotide probe unique to Cryptosporidium parvum DNA, has been reviewed by Wang et al. (1997). A8.4.3Chappell et al. (1997a) describe a study to assess whether DNA sequence variations were related to infectivity in vivo. The Harley Moon strain was compared with the TAMU isolate and current data suggest that genetic variability revealed by random amplified polymorphic DNA does not correlate with differences in oocyst infectivity in mice and humans.
A8.4.4 Vesey et al. (1997) used fluorescence in situ hybridisation (FISH) with a Cryl probe targeted to 18S ribosomal RNA to produce sporozoite fluorescence. The technique was shown to correlate with excystation and be parvum specific, and could be combined with immunofluorescence for detection. A rapid method for the extraction, amplification and detection of Cryptosporidium parvum DNA is described by Wick (1997). Strand displacement amplification uses biotin labelled primers and the amplicon is captured on microtitre plates using complimentary oligonucleotides. Detection is with horseradish-peroxidase streptavidin. Calomiris (1997) describes the use of compound D7 to enhance the recovery of oocysts from seeded turbid waters. As well as improving percoll/sucrose flotation recovery by 2 to 6 fold, compound D7 improves the sensitivity of DNA-based detection by preventing inhibition. Chung et al. (1997) describe an improved method using 293µm diameter, 8.0mm pore size cellulose acetate membrane filtration followed by solution of the membrane in acetone, DNA extraction and amplification. The overall sensitivity of the method was 100 oocysts per 100 litres. Smith et al. (1997) used the combination of IMS to remove oocysts from inhibitory water concentrates with PCR to detect low levels (0.003-0.015 per litre) in raw waters.
A8.4.5 Deere et al. (1997) describe a fluorescent in-situ hybridisation (FISH) technique, requiring only 1 hour for labelling. The technique is species specific and can demonstrate viability by targeting 18S ribosomal RNA.
A8.5 Viability
A8.5.1 Fricker et al. (1997c) describe an AWWARF and UK DWI joint funded project to assess methods for the determination of viability using CD-1 mice, excystation and vital dyes during disinfection studies. The project is being undertaken in the USA and UK during 1997 and 1998. Smith et al. (1997) investigated the criteria for using neonatal CD-1 mice for infectivity studies. Variability of response to infection was demonstrated and parameters such as variation in infective dose, choice of the method for mouse analysis and stress could all influence the results obtained. Slifko et al. (1997) describe a foci detection method (FDM) using slide cultures of human ileocaecal adenocarcinoma (HCT-8) cells. Infection was determined by immunofluorescence. As few as 10 oocysts have been observed to set up infections.
A8.5.2 Jenkins et al. (1997), in comparing dye permeability using DAPI/PI with excystation and mouse infectivity, demonstrated that the dye permeability assay as an indicator of potential viability and infectivity was a useful tool. Belsoevic et al. (1997) described a procedure for determining viability using SYTO-9, hexidium and MPR7 1059. Viability was related to animal infectivity but not excystation. Staining was not affected by disinfectants. Black et al. (1996) used dye exclusion with DAPI and PI, excystation and mouse infectivity to assess viability after disinfection. Dye exclusion and excystation were found to give comparable results but overestimated viability. Mouse infectivity was considered the most reliable measure. Campbell et al. (1997a) found that following exposure of Cryptosporidium oocysts to low levels of ozone, the vital dye assay significantly over-estimated the viability of oocysts. With excystation the released sporozoites were non-motile and misshapen suggesting non-viability. Sporozoite to oocyst ratios were also found to be variable.
A8.6 Methodology reviews
A8.6.1 Watanabe (1996) discussed the validity of current test procedures for Cryptosporidium and Giardia and the newer test methods of flow cytometry, electrorotation assay, IMS and PCR. Jakubowski et al. (1996) also review methods in a report by the Working Group on Waterborne Cryptosporidiosis. Viability assessment, surrogate indicators, sampling and processing techniques are reviewed. The report also presents relevant information on available antibodies.Smith and Hayes (1997) review the limit of current isolation techniques, suggest modifications and additions and examine the development of new methods and the assessment of oocyst viability. Fricker and Clancy (1998) briefly review advances that are being made in Cryptosporidium detection methods including new filter technologies, immunomagnetic separation, flow cytometry, nucleic acid probes and viability testing. They conclude that whilst significant advances have been made there is much still to be done before a standard protocol for all water types can be produced.
A8.7 Raw and treated water contamination
A8.7.1 Ong et al. (1996) studied two adjacent catchments for Giardia and Cryptosporidium. Headwaters were not contaminated but creeks and water intakes contained Giardia, consistent with multiple source contamination. Both Giardia and Cryptosporidium were found in one catchment coinciding with calving activity. Wallis et al. (1996) found Giardia in 73% of raw sewage samples, 21% of raw water samples and 18.2% of treated water samples. The corresponding values for Cryptosporidium were 6.1%, 4.5% and 3.5%.
A8.7.2 Karanis and Seitz (1996) analysed raw, treated and backwash water from six treatment plants in Germany. Of the drinking water samples, 21% were positive for Giardia and 36.4% for Cryptosporidium, while 84% of backwash waters were positive for Giardia and 82% for Cryptosporidium. In the course of epidemiological studies of raw and treated water in southern Germany, Wagner-Wiening et al. (1998) found C. parvum oocysts in 35 out of 89 raw water samples and in 10 out of 29 treated water samples, all of which were derived from lake waters. In all cases the concentrations were below 10 oocysts per 100 litres of water, and there was no recorded outbreak of cryptosporidiosis. Chauret et al. (1995) analysed raw waters for the parasites together with a range of indicators. There was some correlation between Cryptosporidium and enterococci, and between Giardia and somatic coliphages and algae. These were not general but were catchment-specific. There was no correlation between Cryptosporidium and Clostridium perfringens.
A8.7.3 LeChevallier and Norton (1995) provide results of the American Water System's monitoring for surface and potable waters. A prevalence rate of 53.9% for Giardia and 60.2% for Cryptosporidium in surface waters is reported. The validity of the test procedures is examined and the importance of the Disinfectants/Disinfection By-Products Rule not jeopardising microbiological quality is stressed. A South African study of sewage, raw water and drinking water by Kfir et al. (1995) revealed that the average values for Giardia in 10 litres of sewage, effluent, surface water and treated water were 130, 120, 30, and 2 respectively. Values for Cryptosporidium were approximately one quarter of these.
A8.7.4 Hancock et al. (1997) note that in the 12 most recent outbreaks of Cryptosporidium, 33% were traced to contaminated wells. In addition, in 1993-94, 40% of outbreaks with both parasites were traced to groundwater. Their most recent survey showed that 7 of 74 wells contained Giardia (18 cysts per 100 litres, average) and 17 contained Cryptosporidium (41 oocysts per 100 litres, average).
A8.7.5 Norton (1997) increased the frequency of monitoring of a raw water from monthly to weekly/fortnightly to assess whether low frequency monitoring underestimated oocysts levels. This was found to be the case in that more than 50% of the short-term evaluation samples for Cryptosporidium had greater levels than the monthly samples (up to 14 times higher). A8.7.6In a study of waters and effluents in Israel, Zuckerman et al. (1997) found 12 of 15 stream samples were positive for Cryptosporidium (0.04-1.9 oocysts per litre) and eight for Giardia (0.05-0.78 cysts per litre). Four out of 6 samples of a drinking water reservoir were also positive for Cryptosporidium (0.3-1.09 oocysts per litre) and five were positive for Giardia (0.135-16.2 cysts per litre). Sewage samples were positive and one sample of cowshed effluent contained 3,630 oocysts per litre.
A8.7.7 Crockett and Haas (1997) describe a systematic approach to sources of protozoa in catchments, and those conditions which could lead to increases in the concentrations of protozoa in surface waters, and to challenges to water treatment. In addition they discuss the variations in sample collection and analysis in relation to the collection of data for the Enhanced Surface Water Treatment Rule (Crockett and Haas 1995). The authors note that the consequences of poor monitoring could result in expensive and unnecessary water treatment. States et al. (1997) detail the monitoring of two rivers in the US for Giardia and Cryptosporidium. The parasites were detected in more than 50% of river samples and although Giardia was not detected in the treated water, small numbers of Cryptosporidium were occasionally found, and higher numbers were found in the backwash water. Atherholt et al (1998) studied the effect of rainfall on the concentrations of Cryptosporidium oocysts and Giardia cysts in the Delaware river. Rainfall was a significant factor increasing concentrations of both organisms. These increases were associated with higher turbidity caused by resuspension of river and storm drain sediments and surface run-off.
A8.7.8 LeChevallier et al. (1997) examined the inlet and outlet of six open finished-water reservoirs. Results for parasites and indicator bacteria increased through the reservoir. Nearly all the cysts and oocysts detected were either empty or the internal structures were poorly defined. They concluded that the health risks were low. Craun et al. (1997) compared the outbreaks of waterborne disease in areas where the USEPA maximal contaminant level (MCL) for total coliforms had been exceeded. The violation rate was not significantly different between community systems that experienced an outbreak and those that did not. They conclude that to safeguard the public against waterborne disease, microbiological monitoring must be supplemented with periodic sanitary surveys and activities that ensure adequate water quality.
A8.7.9 Jarmey-Swan et al (1997) tested raw and treated waters, effluents and sludge for Cryptosporidium in KwaZulu-Natal. Flocculation and immunofluorescence were used for detection. Faecal samples from two hospitals were also examined. Raw water data ranged from 0-80 oocysts per litre with the highest concentrations in the summer months (rainfall). A wastewater effluent contained up to 150 oocysts per litre, a pre-thickened sludge 7.0 x 105 and a post-thickened sludge 0.25 x 104 oocysts per litre. About 10% of patients' stools were positive, and 35% of children's, with the highest incidence during summer rainfall.
A8.8 Water treatment
A8.8.1 Daniel et al. (1996) describe a risk assessment made in the USA, studies of Cryptosporidium and Giardia removal at activated sludge and drinking water plants in France, and Japanese research examining the risk of Echinococcus multilocaris infection in water. The French study concluded that membrane filtration was needed for completely reliable removal of parasites and the Japanese study concluded that risk of infection was low. Hancock et al. (1996) suggest using microscopic particulate analysis (MPA) to assess water treatment plant performance as an alternative to parasite detection. This can be done by centrifugate pellet and particulate count reduction between raw and treated water samples. Powell (1996) describes a membrane-based filtration for water treatment using 0.2µm membranes. The technique is suitable for surface waters, groundwaters and backwash water, removing colour and suspended solids as well as bacteria and parasites. Bernhardt and Clasen (1996) discuss the optimisation of water treatment regimes to prevent breakthrough of Giardia and Cryptosporidium into treated water supplies.
A8.8.2 Ongerth and Pecoraro (1995) used laboratory-based experiments to look at parasite removal from alum coagulant dosed waters using optimal and sub-optimal doses. Dosed waters were fed to a triple-media filter of anthracite coal, silica sand and garnet sand. Removal ofGiardia ranged from 2.7 to 3.1 logs and Cryptosporidium from 3.05 to 3.6 logs. Halving the coagulant reduced the removal to 1.3 and 1.5 logs respectively. Jacangelo et al. (1995) investigated microfiltration and ultrafiltration for the removal of Giardia, Cryptosporidium and MS2 coliphage. Removal was increased by coating membranes with kaolinite. The influence on coagulation practices on the elimination of particles is reviewed by Lind (1997) in four case studies. Polyaluminium chloride out-performedcompetitor coagulants in terms of filter run-length, build-up of headloss, length of time to breakthrough, and particle count reduction. Dissolved air flotation with iron dosing was shown to remove 3.7 logs of Cryptosporidium under optimum conditions by Plummer et al. (1995).
A8.8.3 By addressing problems such as poor coagulant dosing control, inadequate rapid mixing processes, poor monitoring of individual filters, insufficient wastage after backwashing, unreliable turbidity measurement, inadequate operator knowledge; the use of dirty filters in part-time units, poor process monitoring, and using filter run time as the sole criterion for backwashing, Consonery et al.(1997) raised the acceptable performance of treatment plants in Pennsylvania from 39% to 91% over an eight-year period. Positive presumptive Cryptosporidium samples fell from 35% to below 5%. A post-filtration ninetieth percentile particle count below 10 per ml in the 3-18-µm size range was considered necessary to minimise breakthrough of pathogenic protozoa.
A8.8.4 Turbidity, UV absorption and dissolved organic carbon were suggested as surrogate parameters for analysis. Yates et al. (1997) used bench-scale and pilot- scale studies to optimise coagulant and polymer doses for particle and turbidity removal. Further pilot-scale work will include dual or tri-filtration media. Aerobic spores will be used as a surrogate for determining optimisation. Cryptosporidium seeding and removal will be used once conditions are optimised. Additional testing will include evaluation of pre-oxidant dosing (chlorine or ozone). Using a large filter pilot plant in Israel, Hatukai et al. (1997) monitored the effect of different filtration velocities, grain sizes, pre-oxidant types and flocculant doses. Approximately 1.7 and 2 log removals of Giardia-sized particles were achieved through filtration alone and through sedimentation and filtration, respectively. For Cryptosporidium, these values were 1.5 and 1.9 logs respectively. The most important parameters were pre-oxidant type, and dosing rate of alum and a cationic polymer. Chlorine dioxide was more efficient than chlorine. Ongerth and Hutton (1997) used laboratory-scale tests to determine the effectiveness of diatomaceous earth (DE) filtration in removing Cryptosporidium oocysts from raw water. Reductions were higher with finer, less permeable DE, and with a higher filtration rate for all DE grades.
A8.8.5 Payment (1998) suggests that the spores of Clostridium perfringens could be used as indicators of the presence of Cryptosporidium oocysts because they were an indicator of faecal pollution. Additionally, since they were relatively resistant to inactivation they were also a good indicator of the efficiency of treatment. Rice et al. (1996) assessed the value of aerobic spores as indicators of treatment efficiency. It was concluded that these spores were useful surrogates although being smaller than oocysts they would underestimate removal by filtration processes. The use of aerobic spores for assessing the efficiency of drinking water treatment has recently been reviewed by United Kingdom Water Industry Research Limited (UKWIR, 1998). Particle counting, turbidity and bacillus spores were compared as surrogates for Cryptosporidium by Fox (1997b). Jar tests and a pilot-scale plant were used to evaluate flocculation and filtration. Spiking with Bacillus subtilis spores and Cryptosporidium oocysts was also done. Scott et al. (1997) are studying a full-scale treatment plant to determine the removal of Cryptosporidium, aerobic spore formers and particles to optimise treatment processes and to provide methods for treatment plant evaluation. Hijnen et al. (1997) used spores of sulphite-reducing clostridia in raw water as a surrogate for parasite removal in a water treatment plant. Flotation, filtration, ozone and GAC gave an approximate 3-log reduction.
A8.8.6 Gregory (1998) argues that the possible presence of Cryptosporidium means that even low levels of particles in drinking water are of concern, and that traditional turbidity measurements are insensitive in the size range of oocysts. He discusses the forms of turbidity measurements, and the alternatives which have greater sensitivity. Particle counters were evaluated by Hall and Croll (1997) as tools for monitoring and improving plant performance with regard to Cryptosporidium risk at a pilot-plant facility. Particle counters gave a more sensitive indication of particle breakthrough from filters compared with turbidimeters. The Diverse fine particle monitor has been described by Roth (1998). This instrument continuously monitors particles in the range 2-20 µm and if the particle concentration exceeds the norm an alarm sounds. Li et al .(1997) observed in field-scale systems a high linear correlation was between removals of 4-6 mm polysty ene microspheres and Cryptosporidium parvum oocysts. Other potential surrogates, including 4-6 µm particle counts, 1-25µm particle counts and turbidity, proved less reliable.
A8.8.7 Frederiksen (1997) augmented conventional water treatment with wound fibre nanofiltration and monitored particle counts, turbidity, spore and plate counts over a 15-month period. Membranes remained intact despite over 50 acid washings. Further studies will include parasite monitoring. Drodz and Schwartzbrod (1997) used a pilot tangential microfiltration system (0.2µm) for the removal of oocysts added to large volumes of river water. Removal of >4.3 logs was observed in nine trials. The viability of the oocysts in the filter concentrate was unaltered but washing the membrane with sodium hydroxide and nitric acid significantly reduced viability. The development of a new two-stage process for Cryptosporidium removal has been described by Bell and Pearce (1997). The oocysts were removed from the water supply by a spirally-wound backwashable depth filter and then destroyed by in situ vacuum steam pasteurisation of the filter element. Johnson (1998) described the Memtec membrane control strategy. Monitoring of process integrity and the identification and isolation of faulty modules was required to ensure 4 log unit (or better) removal of Giardia or Cryptosporidium .
A8.8.8 Drury and Lloyd (1997) discuss the difficulties of enumerating oocysts, the use of laboratory or pilot-plant studies for real-life situations and the failure of surrogates to mimic Cryptosporidium. Good water treatment regimes and good liaison between water utilities, the Environment Agency and Environmental Health officials are stressed. They also describe work which shows that conventional water treatment may cause oocysts to clump, and consider survival in agricultural wastes. Oxenford et al (1997) have produced a report based on findings of an AWWARF sponsored research project and other international research to provide water treatment managers with bottom line' information on Cryptosporidium.
A8.9 Disinfection
A8.9.1 Fayer et al (1996) used saturated gaseous atmospheres of ammonia, carbon monoxide, ethylene oxide, formaldehyde and methyl bromide to challenge purified oocysts of Cryptosporidium parvum at 21-23ºC for 24 hours. Oocysts exposed to ammonia, ethylene oxide or methyl bromide were non-infective for BALB/c mice whilst formaldehyde and carbon monoxide exposed oocysts were infective. Quinn et al (1996) used dielectrophoresis at two frequencies to demonstrate ozone inactivation of Cryptosporidium oocysts. Aqueous chlorine, chlorine dioxide, sodium thiosulphate, chlorite and chlorate were assessed by Liyanage et al (1997a,b,c) as disinfectants against Cryptosporidium parvum at pH 8.0 and 22ºC. Infectivity was assessed using CD-1 mice. Only chlorine dioxide was shown to be effective. Gyurek et al (1997) examined chlorine and monochloramine inactivation of Cryptosporidium parvum oocysts at pH 6.0 and 8.0 and 22ºC. CD-1 mice were used to assess infectivity. Design graphs were produced to aid engineers to establish disinfection requirements for controlling Cryptosporidium in drinking water.
A8.9.2 Venczel et al (1997) compared an electrochemically produced oxidant solution (MIOX, LATA Inc.) and free chlorine as disinfectants against Cryptosporidium and Clostridium perfringens spores at pH 7.0 and 25ºC. Doses of 5mg.l-1 were used with contact times of up to 24 hours. The mixed oxidant gave a 3-log inactivation of oocysts and spores in four hours whilst free chlorine had no effect on oocysts and gave a 1.4-log reduction of Clostridium perfringens.
A8.9.3 Studies of the relationship between the inactivation of Cryptosporidium in natural waters and different combinations of different disinfectants are being done by Oppenheimer et al (1997). Ozone, chloramine and chlorine are being tested over a wide range of temperatures. Mouse infectivity will be used to assess viability. In bench-scale experiments, Finch et al (1997a) found that pre-treatment of oocysts with ozone enhanced the disinfectant activity of free chlorine. A similar effect was found for pre-treatment with free chlorine followed by monochloramine. Viability was assessed by mouse infectivity. Additional data is described in Liyanage et al (1997b). Studies of the inactivation by sequential addition of ozone and chlorine dioxide of Cryptosporidium parvum in bench scale experiments are reported Liyanage et al (1997c). Suspensions of C. parvum were exposed to chlorine dioxide or to ozone followed by chlorine dioxide. Oocyst viability was determined from infectivity studies and showed that inactivation was synergistic.
A8.9.4 LeChevallier (1997) proposes to look at Cryptosporidium inactivation using a new system for generating pure chlorine dioxide. Two pH levels (6 and 8), two disinfectant concentrations (0.5 and 1.5mg.l-1) and two temperatures (10 and 20ºC) will be assessed. Viability will be assessed by DAPI/PI staining, excystation and tissue culture. Pilot studies will also examine the levels of disinfection by-products. Miltner et al (1997), working with a pilot-scale ozone plant, found that Bacillus subtilis spores were the most difficult micro-organisms to inactivate followed by indigenous spores>Cryptosporidium>Giardia>poliovirus. Inactivation of spores was found to be temperature dependent.
A8.9.5 Campbell et al (1995) studied ultraviolet radiation in a novel apparatus. Oocysts were removed by filtration, exposed to ultraviolet, backflushed from the filter and the process repeated. A reduction in viability by a factor of 100 was noted. Clancy (1997b) examined pulse and medium intensity UV, plasma sparker technology (sonoluminescence), electron beam and pulsed electric field systems as alternative disinfection technologies. Viability was determined by mouse infectivity. Only UV methods were found to inactivate oocysts. In a further study using a full scale plant treating 400 gpm, UV gave a 4.1 log reduction in oocyst viability using mouse infectivity (Clancy et al 1997b). Assays by DAPI/PI and excystation gave only a two log reduction.
A8.10 Prevention of infection
A8.10.1 A Working Group on Waterborne Cryptosporidiosis (WGWC) has produced guidelines on issuing and rescinding boil-water orders (Pontius 1996). The paper recommends forming a local task force to evaluate factors such as source water quality, treatment effectiveness, distribution system integrity, finished water quality and epidemiological evidence before issuing or removing boil water advice.
A8.11 Risk assessment
A8.11.1 Gale (1996) discusses the wide range of pathogens which may be in water and which should be modelled. Complications arise around pathogendensities in water and whether organisms are randomly distributed or clumped. The author suggests that emphasis should be shifted away from dose-response curves and towards defining exposures to pathogen doses when making risk assessment models. The major contributing factors for human infection from drinking water are discussed by Teunis et al (1997). They conclude that the uncertainty in the estimated removal efficiency of treatment processes is more important than other factors. The aptness of water quality models which assume that waterborne pathogens are randomly dispersed in treated water, and that therefore their presence in any one sample could be expected to be mirrored in any other from the same batch, is challenged by Gale et al (1997), following experimental work using aerobic spores as surrogates for Cryptosporidium oocysts. In samples taken from an operational works there was evidence of clustering such that assessments of risk to human health were invalidated. Le Blanq (1997) considers that risk assessment for infection from drinking water can be based on seroprevalence or epidemiological data. Her risk assessment results suggest that tap water has a minor role to play for Giardia but a potentially significant role for Cryptosporidium.
A8.11.2 Medema (1997b) assesses all the relevant data necessary to build a risk model. Factors include concentration of the parasite in the raw water, recovery efficiency of the detection method, treatment removal and daily consumption of unboiled water. He concludes that in general risk is low but there are a few instances when risk may be high and here, reliability of water treatment needs to be controlled. Miller et al (1997) collected data on risk factors for Cryptosporidium infection in New York. Of 475 cases in 1995, >80% had a compromised immune function and 69.8% were listed in the AIDS registry. The data are not case controlled.
A8.12 Outbreaks
A8.12.1 A large number of outbreaks have now been documented. The earliest ones occurred in the early 1980s (Badenoch 1990) but outbreaks still continue and despite our improved understanding of the parasite, its distribution in the environment and its removal by water treatment, outbreaks continue. A number of surface water derived outbreaks have occurred in the United Kingdom. Two early ones are reported in Hull and in Sheffield. The cause of the latter was never documented but environmental investigations by Chapman et al (1997) suggested surface water contamination by demonstration of the parasite in the catchment to the supply. A large outbreak in Oxford and Swindon in 1989 (Richardson et al 1991) focused attention on the parasite as a waterborne problem in the United Kingdom. A smaller outbreak occurred in Bradford in 1992 (Atherton et al 1995) in a part of the city which received treated water from a moorland reservoir. A case control study demonstrated an association between illness and consumption of tap water from the source and cryptosporidial oocysts were recovered from treated water. During 1997 the Drinking Water Inspectorate identified 5 notifications of increases in cases of cryptosporidiosis as being associated with water supply (DETR 1998). The most serious was in north London where there were 345 confirmed cases which appeared to be related to a ground water supply (DWI 1998).
A8.12.2 Fox and Lytle (1996) report on the USEPA investigations into the Milwaukee outbreak. Factors contributing to the outbreak are discussed and recommendations for improving the operation of the treatment works are summarised. Roefer et al (1996) report the investigations into an outbreak of cryptosporidiosis in the HIV-infected population in Las Vegas in 1994. There were no apparent treatment deficiencies or breakdowns. AIDS patients were considered to be at greater risk of infection through drinking tap water as opposed to bottled or filtered water.
A8.12.3 Solo-Gabrielle and Neumeister (1996) review cryptosporidiosis outbreaks in the USA. Most people affected received surface water supplies and all treatment facilities were complying with federal and local regulations. Interestingly, wastewater was implicated as the source of contamination of raw or treated waters for about half the outbreaks. A case-control study of adults with HIV infection revealed that those who drank tap water were four times more likely to have cryptosporidiosis than those who drank bottled water (Goldstein et al 1996). Weidenmann et al (1996) note that so far there have been no recorded outbreaks of Cryptosporidium in Germany. The investigation suggested that consumption of raw milk and contact with animals were major sources of infection rather than consumption of contaminated drinking water. Fewtrell and Delahunty (1995) report that between 1987 and 1992, there were 497 laboratory confirmed cases of Cryptosporidium in Blackpool, Wyre and Fylde. There was no correlation with water supply but water sport participation and animal contact were risk factors.
A8.12.4 Bridgman et al (1995) describe an outbreak in north-west England in 1993 giving 47 cases of Cryptosporidium. One groundwater source drained water from a field contaminated with animal faeces where there were fissures from mining subsidence. Water analysis was negative but a case-control study showed significant association with drinking unboiled tap water. Maguire et al (1995) describe the investigation of an outbreak of 44 cases of Cryptosporidium in south London in 1991. Fifteen primary cases were supplied by one water utility. There was no association with the amount of tapwater drunk and no water quality problems had been identified by the utility. Steiner et al (1997) review Cryptosporidium parvum, Giardia, Entamoeba histolytica and Cyclospora cayetanensis as causes of waterborne diarrhoeal disease. Fox (1997a) has researched waterborne outbreaks in the USA and the treatment lapses which allowed oocysts into the drinking water. The data can be used to assist utilities to manage water treatment systems to minimise the risk of outbreaks.
A8.12.5 Frost (1997) plans to study seroprevalence of antibodies against two specific Cryptosporidium antigens. Of the two populations selected, one receives water from a heavily contaminated surface source and the other from a deep well source. Five hundred sera will be collected and tested over a five-month period. An additional study is reported using surplus sera from NHANES III involving seven cities (Frost 1997). Statistically significant differences were observed possibly due to geographical variation in endemic levels of infection and there was possibly a significant contribution from waterborne transmission. Craun et al (1998) reviews 35 outbreaks of cryptosporidiosis in the United States of America and the United Kingdom. They conclude that available epidemiological data is inadequate to assess endemic waterborne risks and that analytical rather than ecological epidemiological surveys must be carried out to assess these risks.. They also suggest that protective immunity is an important consideration when assessing endemic risks. This immunity may be acquired from sporadic low-level exposure to oocysts in the drinking water which do not cause an outbreak. Craun et al (1998) believe that evidence in support of protective immunity can be obtained from clinical studies in which less severe symptoms were observed in volunteers re-challenged with oocysts.
A8.13 Infection
A8.13.1 Chappel et al (1997b) infected volunteers and used the immunological response to understand the host-parasite interaction. A challenge to 29 serologically negative adults with 30-1,000,000 oocysts (Iowa strain) resulted in 18 with oocysts in faeces and of these, seven had diarrhoeal symptoms. Faecal IgA was positively associated with faecal shedding. Serum response did not correlate with shedding or illness. Haas et al (1996) evaluated data from a study of infection and illness in human volunteers subjected to controlled exposure to oocysts of Cryptosporidium parvum. The apparent acceptable oocyst concentrations in potable waters is 0.003 per 100 litres. Over 73% were positive for IgM, 45% for IgA and 21% for IgG. One year on, 19 were re-challenged with 500 oocysts. Only three had evidence of oocyst shedding and seven had diarrhoea. Swabby-Cahill and Cahill (1997) used C57B1/6 mice for routine passage and stock production of Cryptosporidium for investigating minimum infective dose. A full review of the epidemiologic aspects of human cryptosporidiosis has been published by Meinhardt et al (1996).
A8.14 Survival
A8.14.1 Heisz et al. (1997) suspended oocysts in river water in the dark at different temperatures. Oocysts were counted using a counting chamber and viability assessed by excystation. At higher temperatures there was a 2.5 log reduction in viability at 30 days and a 1.2 log reduction at lower temperatures in the same period. Abbeaszadegan (1997) studied the survival of Cryptosporidium parvum and Giardia muris in natural waters, sludges and sediments. Giardia rapidly became undetectable in river water (3 weeks) whereas Cryptosporidium numbers were only reduced by 0.6 logs. Aged oocysts and cysts were more susceptible to chlorine than fresh ones. Giardia was very susceptible to freezing. Viability was assessed by excystation.
A8.14.2 Medema et al (1997a) found that the time required for a 1-log reduction of Cryptosporidium in river water was 40-160 days at 15ºC and 100 days at 5ºC. Die-off of Escherichia coli and enterococci was faster than Cryptosporidium but Clostridium perfringens die-off was slower. Johnson et al (1997) found that Giardia cysts were inactivated by high salinity, where the contents hyperplasmolyse, and by light (cysts survive for 72 hours in the dark and three hours in the light). Two month old oocysts required 13-16 days for 90% reduction whereas four-month old oocysts required three to four days. The order of survival was Cryptosporidium>poliovirus>Giardia>Salmonella.
A8.15 Private water supplies
A8.15.1 Clapham (1997) examined 15 private water supplies. Cryptosporidium was found in 20 (14%) of samples taken and nine of the 15 supplies (60%) contained oocysts during the survey. Giardia was present in eight of the supplies. Enterococci and sulphite reducing clostridia were significantly correlated to Cryptosporidium.
A8.15.2 An outbreak of Cryptosporidium and Campylobacter was described by Duke et al (1996) in a private water supply with 43 people affected. Campylobacter jejuni was isolated from five cases, Cryptosporidium from four cases and both pathogens from two cases. Heavy rainfall had occurred several days before the outbreak and water samples had contained high levels of Escherichia coli. Three dead lambs were found in a collecting chamber from a spring supplying the supply but these were removed before they could be investigated.
A8.16 Swimming pools
A8.16.1 The recent occurrence of cryptosporidiosis at five public pools led Kebabjian (1995) to make a number of suggestions on the management of faecal contamination in pools. Closure for up to one day is suggested to permit proper filtration and disinfection of pool water. An increase of Cryptosporidium incidence from 0.5-1% to 15-17% was investigated by Medema (1997c). Drinking water, distribution systems and water treatment operations were satisfactory but a case control study revealed that swimming in pools was the only risk factor. MacKenzie et al (1995) detail an outbreak of cryptosporidiosis involving 51 people at a hotel. Use of the swimming pool was the only significant risk factor. Unrecognised faecal accidents were suggested as the cause.
A8.17 Wastewater
A8.17.1 Rider et al (1996) described a wastewater treatment system which removes 99.9% of Giardia cysts and Cryptosporidium oocysts. The filter system consisted of a dual-stage, deep bed sand filter. Stadterman et al (1995) found that a laboratory activated sludge plant removed 98.6% of seeded Cryptosporidium parvum oocysts. In a comparison of different treatment regimes, activated sludge and anaerobic digestion were found to be the most effective means of removing oocysts, the latter destroying 99.9% in 24 hours. Hirata et al (1997) looked at raw sewage, and primary, secondary and final effluents for Giardia and Cryptosporidium. Cryptosporidium was only found in one sample (28 oocysts per litre) whereas Giardia was found in all samples (125-4,500 cysts per litre). Conventional activated sludge reduced cysts by 2 logs. Clostridium perfringens was suggested as a good surrogate. Bukhari et al (1997) produced data to show small numbers of oocysts in both the influent and effluent samples from sewage works whereas Giardia cysts were detected more frequently and at higher concentrations. Oocysts were only detected at one site in sewage sludge whereas cysts were found at all the sites examined.
A8.17.2 Madireddi et al (1997) constructed a pilot plant to treat a municipal secondary effluent for augmentation of a lake used as a drinking water source. Extensive treatment including ultrafiltration and nanofiltration gave 21-22 log removal of bacteriophages and 8-10 log removal of Giardia and Cryptosporidium. During a one-year study at a water reclamation facility employing biological treatment, sand filtration and chlorination, Rose et al (1996) found that total and faecal coliforms were reduced by >7 logs, coliphages and enteroviruses by >5 logs and Giardia and Cryptosporidium by >3 logs. The risk of infection by exposure to 100 ml of water was calculated as between 10-6 and 10-8.
A8.18 Faecal material
A8.18.1 Bukhari and Smith (1997) discuss ways in which agricultural wastes could pollute water, and provide information on survival of oocysts in naturally contaminated materials. Bodley-Tickell et al (1997) found Cryptosporidium in almost 70% of rural surface waters tested. Numbers were found to be higher in autumn, coinciding with calving, slurry spreading and rainfall. Levels ranged from 0-16.7 oocysts per litre with a mean value of approximately 1.0. The results indicate that wildlife may have a substantial input to small rural waters.
A8.19 Soil
A8.19.1 Mawdsley et al (1996) dosed soil cores in the laboratory with high numbers (108) of Cryptosporidium oocysts. Small numbers of oocysts were detected in the leachate from clay loam and silty loam but not from a loamy sand soil. Variations in leaching were observed with replicate cores. The majority of oocysts were found in the top 2 cm of soils. A8.20 Food
A8.20.1 Harp (1996) demonstrated that oocysts were killed by heating in water and milk to 71.7ºC for 5, 10 and 15 seconds. Viability was assessed by infectivity in mice. Water as a vehicle for various foodborne agents is discussed by Palumbo et al (1997). An overview of wastewater treatment processes is presented and approaches to reconditioning plant processing water for reuse in food processing are included. Chalmers et al (1997) claim the first report of Cryptosporidium oocysts in mussel tissue and suggest that this might be a source of food poisoning.
A8.21 Statistical analysis
A8.21.1 Nahrstedt and Gimbel (1996, 1997) and Gimbel and Nahrstedt (1996) describe a statistical method for determining the reliability of analytical results and a strategy for the improvement of analytical methods. Medema et al (1997b) used a chemical pollutants model to calculate the concentration of oocysts and cysts in surface waters receiving domestic sewage effluent. Calculated figures were found to be in good agreement with actual measurements although the model underestimates the concentrations in agricultural discharges where concentrations may be significantly higher. Sakaji and Chun (1997) outline an integrated action plan for when oocyst counts in waters are higher than historical data. Particular reference is paid to good communication systems.
A8.21.2 Stuart (1997) modelled the effect of body-contact recreation on the concentration of pathogens, including Cryptosporidium, at the outlet to a reservoir under construction. The effects of boating (limited activity) and full recreational activities were modelled.
A8.22 Typing Cryptosporidium
A8.22.1 McLauchlin et al (1997) describe the use of SDS-PAGE Western-blotting analysis to sub-type Cryptosporidium parvum. This and a similar system can be used to recognise multiple types of the parasite and antibodies in sera. The technique has been used to investigate waterborne outbreaks.
A8.22.2 Bonnin et al (1996) used PCR with restriction-fragment length polymorphism (RFLP) to type 23 isolates of Cryptosporidium parvum. Ten calf isolates were shown to have the same profile but 13 human isolates had two patterns, one identical to the calf isolates but the second different. Spano et al (1997) also used PCR with RFLP to distinguish Cryptosporidium wrayii from Cryptosporidium parvum and were able to distinguish two isolates of parvum, one associated with animal and one with human infections. Carroway et al (1996) and Morgan et al (1995) were also able to differentiate human and animal groups, the latter using RADP. In addition, Carroway et al (1997) were able to show that there was a change in the genetic profile of Cryptosporidium parvum following transmission from cattle to humans.
References
Abbaszadegan, M. (1997) Survival of Cryptosporidium oocysts and Giardia cysts in watersheds. Submitted as an abstract to 1997 International Symposium on Cryptosporidium, Newport Beach, California.
Atherholt,T.B, LeChevalier, M.W., Norton, W.D. and Rosen, J.S. (1998) Effect of rainfall on Giardia and Crypto. Journal of American Water Works Association, 90, No.9, 66-80.
Atherton, F., Newman, C.P.S. and Casemore, D.P. (1995) An outbreak of waterborne cryptosporidiosis associated with a public water supply in the UK. Epidemiology and Infection 115, 123-131.
Badenoch J (1990) Cryptosporidium in water supplies. Report of the Group of Experts; Department of the Environment, Department of Health. London, UK. HMSO. 230pp.
Battigelli, D.A. (1997) Viability assessment of Cryptosporidium parvum by an integrated cell culture/RT-PCR method. Submitted as an abstract to 1997 International Symposium on Cryptosporidium, Newport Beach, California.
Bell, J.A. and Pearce, G.K. (1997) Filter process removes cryptosporidial oocysts from water supplies. Water Engineering & Management 144, No.8, 18-19.
Belsoevic, M., Guy, R.A., Neumann, N.F. and Finch, G.R. (1997) Viability assessment of Cryptosporidium parvum oocysts using nucleic acid dyes. Submitted as an abstract to 1997 International Symposium on Cryptosporidium, Newport Beach, California.
Bernhardt, H. and Clasen, J. (1996) Elimination of micro-organisms illustrated with reference to the treatment of reservoir water. GWF-Wasser/Abwasser 137, 109-116.
Black, E.K., Finch, G.R., Taghi-Kilani, R. and Belosevic, M. (1996) Comparison of assays for Cryptosporidium parvum oocysts viability after chemical disinfection. FEMS Microbiology Letters 135, 187-189.
Bodley-Tickell, A., Kitchen, S. and Sturdee, A. (1997) Cryptosporidium parvum in rural surface waters. Proceedings of the Second Symposium on Health-Related Water Microbiology University of Warwick, ed. Morris, R. and Gammie, A., 138-143.
Bonnin, A., Fourmax, M.N., Dubremetz, J.F., Nelson, R.G., Gobet, P., Harly, G., Buisson, M., Puygauthier-Toubas, D., Gabriel-Pospisil, F., Naciri, M. and Camerlynck, P. (1996) Genotyping human and bovine isolates of Cryptosporidium parvum by polymerase chain reaction-restriction fragment length polymorphism analysis of a repetitive DNA sequence. FEMS Microbiology Letters 137, 207- 211.
Bridgman, S.A., Robertson, R.M.P., Syed, Q., Speed, N., Andrews, N. and Hunter, P.R. (1995) Outbreak of cryptosporidiosis associated with a disinfected groundwater supply. Epidemiology and Infection 115, No. 3, 555-566.
Bukhari, Z. and Smith, H.V. (1997) The impact and significance of agricultural waste-derived Cryptosporidium sp. oocysts on contamination of water. Submitted as an abstract to 1997 International Symposium on Cryptosporidium, Newport Beach, California.
Bukhari, Z., Smith, H.V., Sykes, N., Humphries, S.W., Paton, C.A., Girdwood, R.W.A. and Fricker, C.R. (1997) Occurrence of Cryptosporidium spp oocysts and Giardia spp cysts in sewage influents and effluents from treatment plants in England. Water Science and Technology 35, No. 11/12, 385-390.
Calomiris, J.J. (1997) Enhanced recovery of Cryptosporidium parvum from turbid surface waters for detection by DNA amplification. Submitted as an abstract to 1997 International Symposium on Cryptosporidium, Newport Beach, California.
Campbell, A.T., Robertson, L.J., Snowball, M.R. and Smith, H.V. (1995) Inactivation of oocysts of Cryptosporidium parvum by ultraviolet irradiation. Water Research 29,. 2583-2586.
Campbell, A.T. and Smith, H.V. (1997) Immunomagnetic separation of Cryptosporidium oocysts from water samples: round robin comparison of techniques. Water Science and Technology 35, No. 11/12, 397-402.
Campbell, A.T., Anderson, R.L., Robertson, R.L., Parker, J.F.W. and Smith, H.V. (1997a.) Viability of Cryptosporidium oocysts: assessment following disinfection with ozone. 1997 International Symposium on Waterborne Cryptosporidium Proceedings, ed. Fricker, C.R.,Clancy, J.L. and Rochelle, P.A. American Water Works Association, Denver. Co., 97-102.
Campbell, A.T., Gron, B. and Johnsen, S.E. (1997) Immunomagnetic separation of Cryptosporidium oocysts from high turbidity water samples. concentrates 1997 International Symposium on Waterborne Cryptosporidium Proceedings, ed. Fricker, C.R., Clancy, J.L. and Rochelle, P.A. American Water Works Association, Denver, Co., 91-96.
Carroway, M., Tzipori, S. and Widmer, G. (1996) Identification of genetic heterogeneity in the Cryptosporidium parvum ribosomal repeat. Applied and Environmental Microbiology 62, No. 2, 712- 716.
Carroway, M., Tzipori, S. and Widmer, G. (1997) A new restriction fragment length polymorphism from Cryptosporidium parvum identifies genetically heterogenous parasite populations and genotypic changes following transmission from bovine to human hosts. Infection and Immunity 65, No. 9, 3958- 3960.
Chalmers, R.M., Sturdee, A.P., Mellors, P., Nicholson, V., Lawlor, F., Kenny, F. and Timpson, P. (1997) Cryptosporidium parvum in environmental samples in the Sligo area, Republic of Ireland: a preliminary report. Letters in Applied Microbiology 25, No.5, 380-384.
Chappel, C.L. (1997a) Cryptosporidium parvum: comparison of two isolates by RAPD analysisand infectivity in mice and humans. Submitted as an abstract to 1997 International Symposium on Cryptosporidium, Newport Beach, California.
Chappel, C.L. (1997b) Cryptosporidium volunteer studies: what have we learned and where are we going? Submitted as an abstract to 1997 International Symposium on Cryptosporidium, Newport Beach, California.
Chauret, C., Armstrong, N., Fisher, J., Sharma, R., Springthorpe, S. and Sattar, S. (1995) Correlating Cryptosporidium and Giardia with microbial indicators. Journal of American Water Works Association 87, No.11, 76-84. <
Chung, E., Yee, A., DeGrandis, S., Aldom, J., Chagla, A., Palmateer, G., Unger, S., Boleszczuk, M., Brodsky, P., Trevors, J.T. and Lee, H. (1997) Detection of Cryptosporidium parvum oocysts in municipal water samples using the polymerase chain reaction and the Digene SHARP signalTM system. 1997 International Symposium on Waterborne Cryptosporidium Proceedings, ed. Fricker, C.R., Clancy, J.L. and Rochelle, P.A. American Water Works Association, Denver,Co., 71-78.
Clancy, J.L. (1997a) Cryptosporidium monitoring - what do the data mean? Submitted as an abstract to 1997 International Symposium on Cryptosporidium, Newport Beach, California.
Clancy, J.L. (1997b) Innovative electrotechnologies for inactivation of Cryptosporidium. Submitted as an abstract to 1997 International Symposium on Cryptosporidium, Newport Beach, California.
Clancy, J.L., Hargy, T.M. and Schaub, S. (1997a) Improved sampling methods for the recovery of Giardia and Cryptosporidium from source and treated waters. 1997 International Symposiumon Waterborne Cryptosporidium Proceedings, ed. Fricker, C.R., Clancy, J.L. and Rochelle, P.A.American Water Works Association, Denver, Co., 79-86.
Clancy, J.L., Marshall, M.M. and Dyksen, J.E. (1997b) Innovative electrotechnologies for the inactivation of Cryptosporidium. Proceedings of the Second Symposium on Health-Related Water Microbiology, University of Warwick. ed. Morris, R. and Gammie, A., 192-199.
Clapham, D. (1997) The incidence of Cryptosporidium and Giardia in private water supplies, correlatory indicators and the value of the coliform standard in assessing water quality. Proceedings of the Second Symposium on Health-Related Water Microbiology, University of Warwick. ed. Morris, R. and Gammie, A., 220-225.
Consonery, P.J., Greenfield, D.N. and Lee, J.J. (1997) Pennsylvania's filtration evaluation programme. Journal of American Water Works Association 89, No.8, 67-77.
Craun, G.F., Berger, P.S. and Calderon, R.L. (1997) Coliform bacteria and waterborne disease outbreaks. Journal of American Water Works Association 89, No.3, 96-104.
Craun, G.F., Hubbs, S.A., Frost, F., Calderon, R.L. and Via, S.H. (1998) Waterborne outbreaks of cryptosporidiosis. Journal of American Water Works Association, 90, No.9, 81-91.
Crockett, C.S. and Haas, C.N. (1995) Protozoan monitoring: from the ICR to the ESWTR. Journal of American Water Works Association 87, No. 8, 50-59.
Crockett, C.S. and Haas, C.N. (1997) Understanding protozoa in your watershed. Journal of American Water Works Association 89, No. 9, 62-73.
Daniel, P.A., Dumoutier, N., Mandra, V., Tambo, N. and Kamei, T. (1996.) Pathogenic protozoa in raw and drinking water: occurrence and removal. Water Supply 14, No. 3/4, 387-401.
Deere, D., Veal, D., Fricker, C. and Vesey, G. (1997) Automating analytical microbiology. Water and Environment Management 2, No.1, 13.
Deere, D., Vesey, G. and Veal, D. (1996) Rapid microbial analysis using flow cytometry. Australasian Biotechnology 6, No.3, 174-177.
Deere, D., Vesey, G., Dorsch, M., Ashbolt, N., Williams, K. and Veal, D. (1997) Optimisation of in- situ ribosomal RNA labelling of Cryptosporidium parvum in suspension. Proceedings of the Second Symposium on Health-Related Water Microbiology, University of Warwick. ed. Morris, R. and Gammie, A., 144-156.
Dowd, S.E. and Pillai, S.D. (1997) A rapid viability assay for Cryptosporidium oocysts and Giardia cysts for use in conjunction with indirect fluorescent antibody detection. Canadian Journal of Microbiology 43, No. 7, 658-662.
DETR. (1998) Drinking Water 1997 Chief Inspectors statement. Department of the Environment, Transport and the Regions. London, UK: The Stationary Office. Drodz, C. and Schwartzbrod, J. (1997) Removal of Cryptosporidium from river water by crossflow microfiltration: a pilot-scale study. Water Science and Technology 35, No. 11/12, 391-396.
Drury, D.F. and Lloyd A. (1997) Cryptosporidium a Regulators viewpoint. 1997 International Symposium on Waterborne Cryptosporidium Proceedings, ed. Fricker, C.R., Clancy, J.L. and Rochelle, P.A. American Water Works Association, Denver, Co., 369-376.
Duke, L.A., Breathnach, A.S., Jenkins, D.R., Harkis, B.A. and Codd, A.W. (1996) A mixed outbreak of Cryptosporidium and Campylobacter infection associated with a private water supply. Epidemiology and Infection 116, 303-308.
DWI. (1998) Assessment of water supply and associated matters in relation to the incidence of cryptosporidiosis in west Herts and north London in February and March 1997. Drinking Water Inspectorate. London, UK.
Fayer, R., Graczyk, T.K., Cranfield, M.R. and Trout, J.M. (1996) Gaseous disinfection of Cryptosporidium parvum oocysts. Applied and Environmental Microbiology 62, No. 10, 3908-3909.
Fewtrell, L. and Delahunty, A. (1995) The incidence of cryptosporidiosis in comparison with other gastro-intestinal illnesses in Blackpool, Wyre and Fylde. Journal of Chartered Institution of Water and Environment Management 9, No. 6, 598-601.
Finch, G.R. (1997a) Inactivation of Cryptosporidium using single and sequential application of ozone and chlorine species. Submitted as an abstract to 1997 International Symposium on Cryptosporidium, Newport Beach, California.
Fox, K.R. (1997a) Recent waterborne cryptosporidiosis outbreaks: what have we learned. Submitted as an abstract to 1997 International Symposium on Cryptosporidium, Newport Beach, California.
Fox, K.R. (1997b) Monitoring surrogates for controlling Cryptosporidium removal. Submitted as an abstract to 1997 International Symposium on Cryptosporidium, Newport Beach, California.
Fox, K.R. and Lytle, D.A. (1996) Milwaukee's crypto outbreak: investigation and recommendations. Journal of American Water Works Association 88, No.9, 87-94.
Frederiksen, M.M. (1997) Comparison of membrane filtration and conventional water treatment processes for the removal of Cryptosporidium. Submitted as an abstract to 1997 International Symposium on Cryptosporidium, Newport Beach, California.
Fricker, C.R., Clancy, J.L. and Smith, H.V. (1997a) Factors involved in the variation of performance data collected during trials of new methods for protozoan parasites. abstract in Proceedings of the Second Symposium on Health-Related Water Microbiology, University of Warwick. ed. Morris, R. and Gammie, A., 238.
Fricker, C.R, Jonas, A., Crabb, J., Turner, N. and Smith, H.V.(1997b) The concentration and separation of Cryptosporidium oocysts and Giardia cysts using vortex flow filtration and immunomagnetic separation. 1997 International Symposium on Waterborne Cryptosporidium Proceedings, ed. Fricker, C.R., Clancy, J.L. and Rochelle, P.A. American Water Works Association, Denver, Co., 1-8.
Fricker, C.R., Smith, H.V., Marshall., M.M. and Clancey, J.L. (1997c) Comparison of viability/infectivity of Cryptosporidium in disinfection studies. abstract in Proceedings of the Second Symposium on Health-Related Water Microbiology, University of Warwick. ed. Morris, R. and Gammie, A., 240.
Fricker, C.R. and Clancy, J.L (1998) Crypto's protocol prospects. Water Quality International May/June 1998, 11-14.
Frost, F. (1997) A two-city study of Cryptosporidium infection Submitted as an abstract to 1997 International Symposium on Cryptosporidium, Newport Beach, California.
Frost, F., Muller, T. and Caldreron, R. (1997) A survey of Cryptosporidium antibodies using surplus NHANES sera. Submitted as an abstract to 1997 International Symposium on Cryptosporidium, Newport Beach, California.
Gale, P. (1996) Developments in microbiological risk assessment models for drinking water - a short review. Journal of Applied Bacteriology 81, No. 4, 403-410.
Gale, P., van Dijk, P.A.H. and Stanfield, G. (1997) Drinking water treatment increases micro-organism clustering: the implication for microbiological risk assessment. Aqua 46, No.3, 117-126.
Gimbel, R. and Nahrstedt, A. (1996) Predictive capability of analytical data for the occurrence of Giardia and Cryptosporidium in water. GWF-Wasser/Abwasser 137, No.2, 101-104.
Goldstein, S.T., Juranek, D.D., Ravenholt, O., Hightower, A.W., Martin, D.G., Mesnik, J.L., Griffiths, S.D., Bryant, A.J., Reich, R.R. and Herwaldt, B.L. (1996) Cryptosporidiosis: an outbreak associated with drinking water despite state-of-the-art water treatment. Annals of Internal Medicine 124, No. 5, 459-468.
Graczyk, T.K., Cranfield, M.R. and Fayer, R. (1997a) Recovery of waterborne oocysts of Cryptosporidium from water samples by the membrane-dissolution method. Parasitology Research 83, No. 2, 121-125.
Graczyk, T.K., Fayer, R., Cranfield, M.R. and Owens, R. (1997b) Cryptosporidium parvum oocysts recovered from water by the membrane filter dissolution method retain their infectivity. Journal of Parasitology 83, No. 1, 111-114.
Gregory, J., (1998) Turbidity and beyond. Filtration & Separation 35, No.1, 63-67.
Grimason, A.M., Humphries, S., Bukhari, Z., Smith, H.V. and Fricker, C.R. (1997) Where have all the oocysts gone? Losses of Cryptosporidium oocysts during sample preparation. Submitted as an abstract to 1997 International Symposium on Cryptosporidium, Newport Beach, California.
Gyurek, L.L., Finch, G.R. and Belsoevic, M. (1997) Modelling chlorine inactivation requirements of Cryptosporidium parvum oocysts. Journal of Environmental Engineering - ASCE 123, No. 9, 865-875.
Haas, C.N., Crockett, C.S., Rose, J.B., Gerba, C.P. and Fazil. A.M. (1996) Assessing the risk posed by oocysts in drinking water. Journal of American Water Works Association 88, No.9, 131-136.
Hall, T. and Croll, B., (1997) Particle counters as tools for managing Cryptosporidium risk in water treatment Water Science & Technology 36, No.4, 143-149.
Hancock, C.M., Ward, J.V., Hancock, K.W., Klonicki, P.T. and Sturbaum, G.D. (1996) Assessing plant performance using MPA. Journal of American Water Works Association 88, No.12, 24-34.
Hancock, C., Rose, J.B. and Callahan, M.(1997) The prevalence of Cryptosporidium and Giardia in U. S. groundwaters. 1997 International Symposium on Waterborne Cryptosporidium Proceedings, ed. Fricker, C.R., Clancy, J.L. and Rochelle, P.A. American Water Works Association, Denver, Co., 147-152.
Harp, J.A., Fayer, R., Pesch, B.A. and Jackson, G.J. (1996) Effect of pasteurisation on infectivity of Cryptosporidium parvum oocysts in water and milk. Applied and Environmental Microbiology 62, No. 8, 2866-2868.
Hatukai, S., Ben-Tzur, Y. and Rebhun, M. (1997), Particle counts and size distribution in system design for removal of turbidity by granular deep bed filtration. Water Science & Technology 36, No.4, 225- 230.
Heisz, M., Chauret, C., Chen, P., Springthorpe, S. and Sattar, S.A. (1997) In vitro survival of Cryptosporidium oocysts in natural waters. 1997 International Symposium on Waterborne Cryptosporidium Proceedings, ed. Fricker, C.R., Clancy, J.L. and Rochelle, P.A. American Water Works Association, Denver, Co., 171-176.
Hijnen, W.A.M., Houtepen, F.A.P., van den Speld, W.M.H. and van der Kooij, D. (1997) Spores of sulphite reducing clostridia: a surrogate parameter for assessing the effects of water treatment processes on protozoan (oo)cysts? 1997 International Symposium on Waterborne Cryptosporidium Proceedings, ed. Fricker, C.R., Clancy, J.L. and Rochelle, P.A. American Water Works Association, Denver, Co., 115-126.
Hirata, T. and Hashimoto, A. (1997) A field survey on occurrence of Giardia cysts and Cryptosporidium oocysts in sewage treatment plants. 1997 International Symposium on Waterborne Cryptosporidium Proceedings, ed. Fricker, C.R., Clancy, J.L. and Rochelle, P.A. American Water Works Association, Denver, Co., 183-194.
Hoffman, R.M., Standridge, J.H., Prieve, A.F., Cucunato, J.C. and Bernhardt, M. (1997) Using flow cytometry to detect protozoa. Applied and Environmental Microbiology 89, No. 9, 104-111.
Jacangelo, J.G., Adham, S.S and Laine, J.M. (1995) Mechanism of Cryptosporidium, Giardia and MS2 removal by MF and UF. Journal of American Water Works Association 87, No. 9, 107, 121.
Jakubowski, W., Boutros, S., Faber, W., Fayer, R., Ghiorse, W., Lechevallier, M., Rose, J., Schaub, S., Singh, A. and Stewart, M. (1996) Environmental methods for Cryptosporidium. Journal of American Water Works Association 88. No. 9, 107-121.
Jarmey-Swan, C., Bailey, I.W and Howgrave-Graham, A.R. (1997) Detection, occurrence and epidemiology of Cryptosporidium in KwaZulu-Natal, South Africa. 1997 International Symposium on Waterborne Cryptosporidium Proceedings, ed. Fricker, C.R., Clancy, J.L. and Rochelle, P.A. American Water Works Association, Denver, Co., 159-170.
Jenkins, M.B., Anguish, L.J., Bowman, D.D., Walker, M.J. and Ghiorse, W.C. (1997) Assessment of a dye permeability assay for determination of inactivation rates of Cryptosporidium parvum oocysts. Applied and Environmental Microbiology 63, No. 1, 3844-3850.
Johnson, D.C., Enriquez, C.E., Pepper, I.L., Davis, T.L., Gerba, C.P. and Rose, J.B. (1997) Survival of Giardia, Cryptosporidium, poliovirus and Salmonella in marine waters. Water Science and Technology 35, No. 11/12, 261- 268.
Johnson, D.C., Reynolds, K.A., Gerba, C.P., Pepper, I.L. and Rose, J.B. (1995) Detection of Giardia and Cryptosporidium in marine waters. Water Science and Technology 31, No. 5/6, 439-442.
Johnson, W.T. (1998) Predicting log removal performance of membrane systems using in-situ integrity testing. Filtration & Separation 35, No.1, 26-29.
Karanis, P. and Seitz, H.M. (1996) Occurrence and distribution of Giardia and Cryptosporidium in raw and finished waters produced from surface waters. GWF-Wasser/Abwasser 137, No.2, 94-100.
Kebabjian, R.R. (1995) Disinfection of public pools and management of faecal accidents. Journal of Environmental Health 58, No. 1, 8-12.
Kfir, B., Hilner, C., Du Preez, M. and Bateman, B. (1995) Studies on the prevalence of Giardia cysts and Cryptosporidium oocysts in South African water. Water Science and Technology 31, No. 5/6, 435- 438.
Klonicki, P.T., Hancock, C.M., Straub, T.M., Harris, S.I., Hancock, K.W., Alyaseri, A.N., Meyer, C.J. and Sturbaum, G.D. (1997) Crypto research: are fundamental data missing. Applied and Environmental Microbiology 89, No. 9, 97-103.
Le Blanq, S.M. (1997) A framework for assessing the risks of waterborne Cryptosporidium and Giardia. Submitted as an abstract to 1997 International Symposium on Cryptosporidium, Newport Beach, California.
LeChevallier, M.W. (1997) Inactivation of Cryptosporidium by chlorine dioxide: balancing the risks. Submitted as an abstract to 1997 International Symposium on Cryptosporidium, Newport Beach, California.
LeChevallier, M.W. and Norton, W.D. (1995) Giardia and Cryptosporidium in raw and finished water. Journal of American Water Works Association 87, No. 9, 54-68.
LeChevallier, M.W., Norton, W.D. and Atherholt, T.B. (1997) Protozoa in open reservoirs. Journal of American Water Works Association 89, No. 9, 84-96.
Li, S.Y., Goodrich, J.A., Owens, J.H., Willeke, G.E., Schaefer, F.W. and Clark, R.M. (1997) Reliability of surrogates for determining Cryptosporidium removal. Journal of American Water Works Association 89, No.5, 90-99.
Lind, C.B. (1997) Particle counts can benefit from changes in coagulant programs. Water Engineering & Management 144, No.5, 24 and 26-28.
Liyanage, L.R.J., Finch, G.R. and Belosevic, M. (1997a) Effect of aqueous chlorine and oxychlorine compounds on Cryptosporidium parvum oocysts. Environmental Science and Technology 31, No. 7, 1992-1994.
Liyanage, L.R.J., Finch, G.R. and Belosevic, M. (1997b) Sequential disinfection of Cryptosporidium parvum by ozone and chlorine dioxide Ozone Science & Engineering 19, No.5, 409-423.
Liyanage, L.R.J., Finch, G.R. and Belosevic, M. (1997c) Synergistic effects of sequential exposure of Cryptosporidium oocysts to chemical disinfectants. 1997 International Symposium on Waterborne Cryptosporidium Proceedings, ed. Fricker, C.R., Clancy, J.L. and Rochelle, P.A. American Water Works Association, Denver, Co., 41-52.
MacKenzie, W.R., Kazmierczak, J.J. and Davis, J.P. (1995) An outbreak of cryptosporidiosis associated with a resort swimming pool. Epidemiology and Infection 115, No. 3, 545-553.
Madireddi, K., Babcock, R.W., Levine, B., Huo, T.L., Khan, E., Ye, Q.F., Neethling, J.B., Suffet, I.H. and Stenstrom M. K. (1997) Wastewater reclamation at lake Arrowhead, California-an overview. Water Environment Research 69, No. 3, 350-362.
Maguire, H.C., Holmes, E., Hollyer, J., Strangeways, J.E.M., Foster, P., Holliman, R.E. and Stanwell-Smith, R. (1995), An outbreak of cryptosporidiosis in South London: what value the p value? Epidemiology and Infection 115, No. 2, 279-287.
Matheson, Z., Jonas, A., Smith, H.V., Hargy, T., Clancy, J. and Fricker, C.R. (1997) Evaluation of new concentration procedures for the detection of Cryptosporidium and Giardia. Abstract in Proceedings of the Second Symposium on Health- elated Water Microbiology, University of Warwick, ed. Morris, R. and Gammie, A., 244.
Mawdsley, J.L., Brooks, A.E. and Merry, R.J. (1996) Movement of the protozoan pathogen Cryptosporidium parvum through three contrasting soil types. Biology and Fertility of Soils 21, No. 1Ú2, 30-36.
Mayer, C.L. and Palmer, C.J. (1996) Evaluation of PCR, nested PCR and fluorescence antibodies for detection of Giardia and Cryptosporidium species in wastewater. Applied and Environmental Microbiology 62, No.6, 2081-2085.
Mclauchlin, J., Casemore, D.P., Moran, S. and Patel, S. (1998) The epidemiology of cryptosporidiosis: application of experimental sub-typing and antibody detection systems to water-borne outbreaks. Folia Parasitologica 45, 83-92.
Medema, G.J. (1997a) Detection of viable Cryptosporidium and Giardia in water by flow cytometry and propidium iodide staining. Submitted as an abstract to 1997 International Symposium on Cryptosporidium, Newport Beach, California.
Medema, G.J. (1997b) A stochiastic method to assess the risk of Cryptosporidium and Giardia in drinking water. Submitted as an abstract to 1997 International Symposium on Cryptosporidium, Newport Beach, California.
Medema, G.J. (1997c) An outbreak of cryptosporidiosis in the Netherlands: correlation with swimming pools. Submitted as an abstract to 1997 International Symposium on Cryptosporidium, Newport Beach, California.
Medema, G.J., Bahar, M. and Schets, F.M. (1997a) Survival of Cryptosporidium parvum, Escherichia coli, faecal enterococci, and Clostridium perfringens in river water: influence of temperature and autochthonous microorganisms. Water Science and Technology 35, No. 11/12, 249-253.
Medema, G.J. Schijven, J.F., De Nijs, A.C.M. and Elzenga, J.G. (1997b) Modelling the discharge of Cryptosporidium and Giardia by domestic sewage and their dispersion in surface water. 1997 International Symposium on Waterborne Cryptosporidium Proceedings, ed. Fricker, C.R., Clancy, J.L. and Rochelle, P.A. American Water Works Association, Denver, Co., 177-182.
Meinhardt, P.L., Casemore, D.P. and Killer, K.B. (1996) Epidemiologic aspects of human cryptosporidiosis and the role of waterborne transmission. Epidemiologic Reviews 18, No. 2, 118-136.
Miller, J. R., Ashendorf, A., Seeley, A., Mikol, Y.B., Faber Jr, W.W., Calder, J. and Layton, M. (1997) Descriptive epidemiology of cryptosporidiosis in New York City. 1997 International Symposium on Waterborne Cryptosporidium Proceedings, ed. Fricker, C.R., Clancy, J.L. and Rochelle, P.A. American Water Works Association, Denver, Co., 317-328.
Miltner, D., Shukairy, H.M., Rice, E.W., Owens, J.H., Schaefer III, F.W. and Dahling, D.R. (1997) Comparative ozone inactivation of Cryptosporidium and other microorganisms. 1997 International Symposium on Waterborne Cryptosporidium Proceedings, ed. Fricker, C.R., Clancy, J.L. and Rochelle, P.A. American Water Works Association, Denver, Co.,229-242.
Monro, M. (1998) Filter cracks crypto problem. Water Bulletin No.791, 11.
Morgan, U.M., Constantine, C.C., O'Donoghue, P., Melone, B.F., O'Brien, P.A.. and Thompson, R.C.A. (1995) Molecular characterisation of Cryptosporidium from humans and other animals using random amplified polymorphic DNA analysis. American Journal of Tropical Medicine and Hygiene 52(b), 559-564.
Nahrstedt, A. and Gimbel, R. (1996) A statistical method for determining the reliability of analytical results in the detection of Cryptosporidium and Giardia in water. Aqua 45, No3, 101-111.
Nahrstedt, A. and Gimbel, R. (1997) The meaningfullness of analytical results in the detection of Cryptosporidium and Giardia in water. Submitted as an abstract to 1997 International Symposium on Cryptosporidium, Newport Beach, California.
Norton, W.D. (1997) Short-term variability of Giardia cyst and Cryptosporidium oocyst concentrations in a surface water source used as for potable water. Submitted as an abstract to 1997 International Symposium on Cryptosporidium, Newport Beach, California.
Ong, C., Moorehead, W., Ross, A. and Isaac-Renton, J. (1996) Studies of Giardia spp. and Cryptosporidium spp. in two adjacent watersheds. Applied and Environmental Microbiology 62, No. 8, 2798-2805.
Ongerth, J.E. (1997) Comparison of Cryptosporidium and Giardia analysis methods-lab and field studies. Submitted as an abstract to 1997 International Symposium on Cryptosporidium, Newport Beach, California.
Ongerth, J.E. and Hutton, P.E. (1997) DE filtration to remove Cryptosporidium. Journal of American Water Works Association 89, No.12, 39-46.
Ongerth, J.E. and Pecoraro, J.P. (1995) Removing Cryptosporidium using multimedia filters.Journal of American Water Works Association 87, No.12, 83-89.
Oppenheimer, J., Aieta, E.M., Jacangelo, I.J., Najm, I., Selby, D. and Rexing, .(1997) Disinfection of Cryptosporidium: design criteria for North American water agencies. 1997 International Symposium on Waterborne Cryptosporidium Proceedings, ed. Fricker, C.R.,Clancy, J.L. and Rochelle, P.A. American Water Works Association, Denver, Co., 275-280.p Oxenford, J.L., Frey, M.L., Logsdon, G.S. and Hancock, C. (1997) Synthesis report on Cryptosporidium. Submitted as an abstract to 1997 International Symposium on Cryptosporidium, Newport Beach, California.
Palumbo, S.A., Rajkowski, K.T. and Miller, A.J. (1997) Current approaches for reconditioning process water and its use in food manufacturing operations. Trends in Food Science and Technology 8, No. 3, 69-74.
Parton, A., Mendez, F. and Sartory, D.P. (1997). Evaluation of a novel filter for the rapid capture and concentration of Cryptosporidium oocysts from drinking water. Proceedings of the Second Symposium on Health-Related Water Microbiology, University of Warwick. ed. Morris, R. and Gammie, A., 185-191.
Payment, P. (1998) Elimination of Cryptosporidium oocysts: potential indicators.Gas,Wasser, Abwasser78, No.1, 42-44.
Plummer, J.D., Edzwald, J.K. and Kelley, M.B. (1995) Removing Cryptosporidium by dissolved air floatation. Journal of American Water Works Association No. 9, 85-95.
Pontius, F.W. (1996) Guidelines for boil-water advisories. 8Journal of American Water Works Association 88, No.12, 18-102.
Powell, N. (1996) Membrane microfiltration for municipal water treatment. Membrane Technology No. 71, 7-9. Quinn, C.M., Archer, G.P., Betts, W.B. and O'Neill, J.G. (1996) Dose-dependent dielectrophoretic response of Cryptosporidium oocysts treated with ozone. Letters in Applied Microbiology 22, No.3, 224-228.
Rice, E.W., Fox, K.R., Miltner, R.J., Lytle, D.A. and Johnson, C.H. (1996) Evaluating plant performance with endospores. Journal of the American Water Works Association 88 No 9, 122-130.
Rider, D., Suozzo, J. and Collins, C. (1996) Dual-stage filter removes protozoan cysts from effluent. Water Environment and Technology 8, No.6, 15-16.
Richardson, A.J., Frankberg, R.A., Buck, A.C., Selkon, J.B., Colbourne, J.S., Parsons, J.W. and Mayon-W|hite, R.T. (1991) An outbreak of cryptosporidiosis in Swindon and Oxfordshire, Epidemiology and Infection 107, 485-495
Rochelle, P.A., Ferguson, D.M., Handojo, T.J., Deleon, R., Stewart, M.H. and Wolfe, R.L. (1997b) An assay combining cell culture with reverse transcriptase PCR to detect and determine the infectivity of waterborne Cryptosporidium parvum. Applied and Environmental Microbiology 63, No. 5, 2029-2037.
Rochelle, P.A., DeLeon, R., Ferguson, D.M., Stewart, M.H. and Wolfe, R.L. (1997a) Optimisation of an infectivity assay, combining cell culture and PCR for waterborne Cryptosporidium parvum. 1997 International Symposium on Waterborne Cryptosporidium Proceedings, ed. Fricker, C.R., Clancy, J.L. and Rochelle, P.A. American Water Works Association, Denver, Co., 31-40
Rodgers, M.R., Flanigan, D.J. and Jakubowski, W. (1995) Identification of algae which interfere with the detection of Giardia cysts and Cryptosporidium oocysts and a method for alleviating this interference. Applied and Environmental Microbiology 61, No. 10, 3759-3763.
Roefer, P.A., Monscvitz, J.T. and Rexing, D.J. (1996) The Las Vegas cryptosporidiosis outbreak. Journal of American Water Works Association 88, No.9, 95-106.
Rose, J.B., Dickson, L.J., Farrah, S.R. and Carnahan, R.P. (1996) Removal of pathogenic and indicator microorganisms by a full-scale water reclamation facility. Water Research 30, N0.11, 2785-2797.
Roth, S., (1998) Shining a bright new light on crypto. Water Bulletin No.784, 10-11.
Sakaji, R.H. and Chun, D.G. (1997) Oh-oh cysts. 1997 International Symposium on Waterborne Cryptosporidium Proceedings, ed. Fricker, C.R., Clancy, J.L. and Rochelle, P.A. American Water Works Association, Denver, Co., 213-218
Sartory, D.P. (1997) Relationship between the occurrence of Cryptosporidium and bacterial indicators in surface and groundwaters. Proceedings of the Second Symposium on Health-Related Water Microbiology, University of Warwick. ed., R. and Gammie, A., 119-125
Scott, K.N. (1997) Evaluation of Cryptosporidium and surrogate removal through a full-scale treatment plant. Submitted as an abstract to 1997 International Symposium on Cryptosporidium,Newport Beach, California
Shepherd, K.M. and Wyn-Jones, A.P. (1996.) Evaluation of methods for the simultaneous detection of Cryptosporidium and Giardia from water. Applied and Environmental Microbiology 62, No. 4, 1317-1322.
Slifco, T.R., Friedman, D.E., Rose, J.B., Upton, S.J. and Jakubowski, W. (1997) Unique cultural methods to detect viable Cryptosporidium parvum oocysts in environmental samples. Water Science and Technology 35,No. 11/12, 363-368.
Sluter S.D., Tzipori, S. and Widmer, G. (1997), Parameters affecting polymerase chain reaction detection of waterborne Cryptosporidium parvum oocysts. Applied Microbiology and Biotechnology 48, No.3, 325-330.
Smith, H.V. and Fricker, C.R. (1997) How effective is the current method for the analysis of waterborne Cryptosporidium? Proceedings of the Second Symposium on Health-Related Water Microbiology, University of Warwick. ed. Morris, R. and Gammie, A., 170-184
Smith, H.V. and Hayes, C. (1997) The status of UK methods for the detection of Cryptosporidium spp. oocysts and Giardia spp. cysts in water. Water Science and Technology 35, No. 11/12, 369-376.
Smith, H.V., Marshall, M.M., O'Grady, J., Korich, D.G., Olfers, S., Millan, D., Clancy, J., Fricker, C.R., Campbell, B., Bukhari, Z. and Rosen, J. (1997) Usefulness of the CD1 neonatal mouse model for determining the infectivity of Cryptosporidium parvum oocysts. Proceedings of the Second Symposium on Health-Related Water Microbiology, University of Warwick. ed. Morris, R. and Gammie, A., 200-206.
Smith, H.V., Webster, K.A., Parker, J.F.W., Giles, M. and Bukhari, Z. (1997) Development of an immunomagnetisable particle separation (IMS) PCR for the detection of Cryptosporidium parvum oocysts in water concentrates. Submitted as an abstract to 1997 International Symposium on Cryptosporidium, Newport Beach, California.
Solo-Gabrielle, H. and Neumeister, S. (1996) U.S. outbreaks of cryptosporidiosis. Journal of American Water Works Association 88, No. 9, 76-86.
Spano, F., Putignani, L., Mclauchlin, J., Casemore, D.P. And Crisanti, A. (1997) PCR-RFLP analysis of the Cryptosporidium oocyst wall protein (COWP) gene discriminates between C. wrayii and C. parvum and between C. parvum isolates of human and animal origin. FEMS Microbiology Letters 150, 209-217.
Stadterman, K.L., Sninsky, A.M., Sykora, J.L. and Jakubowski, W. (1995) Removal and inactivation of Cryptosporidium oocysts by activated sludge treatment and anaerobic digestion. Water Science and Technology 31, No. 5/6, 97-104.
States, S., Stadterman, K., Ammon, L., Vogel, P,. Baldizar, J., Wright, D., Colney, L. and Sykora, J. (1997) Protozoa in river water: sources, occurrence, and treatment. Journal of American Water Works Association 89, No. 9, 74-83.
Steiner, T.S., Thielman, N.M. and Guerrant, R.L. (1997) Protozoal agents what are the dangers for the public water supply? Annual Review of Medicine 48, 329-340.
Stewart, M., Yates, M., Anderson, M., Gerba, C., DeLeaon, R. and Woldfe, R.(1997) Modelling the impact of body-contact recreation on Cryptosporidium levels in a drinking water reservoir. 1997 International Symposium on Waterborne Cryptosporidium Proceedings, ed. Fricker, C.R., Clancy, J.L. and Rochelle, P.A. American Water Works Association, Denver, Co., 137-146.
Stinear, T., Matusan, A., Hines, K. and Sandery, M. (1996) Detection of a single viable Cryptosporidium parvum oocyst in environmental water concentrates by reverse transcriptase-PCR. Applied and Environmental Microbiology 62,No. 9, 3385-3390.
Swabby-Cahill K.D. and Cahill, A.R. (1997) Infection of immune supressed adult C57BL6 mice as a biologic model to study infectivity and viability of Cryptosporidium parvum oocysts. 1997 International Symposium on Waterborne Cryptosporidium Proceedings, ed. Fricker, C.R., Clancy, J.L. and Rochelle, P.A. American Water Works Association, Denver, Co., 133-136
Teunis, P.F.M., Medema, G.J., Kruidenier, L. and Havelaar, A.H. (1997) Assessment of the risk of infection by Cryptosporidium or Giardia in drinking water from a surface water source. Water Research 31, No.6, 1333-1346.
UKWIR (1998) Use of aerobic spores for assessing the efficiency of drinking water treatment United Kingdom Water Industry Research Limited Project WW-07, 16 pp.
Veal, D., Vesey, G., Fricker, C., Ongerth, J., Le Moenic S., Champion, A., Rossington, G. and Faulkner, B. (1997) Routine cytometric detection of Cryptosporidium and Giardia: recovery rates and quality control. 1997 International Symposium on Waterborne Cryptosporidium Proceedings, ed. Fricker, C.R., Clancy, J.L. and Rochelle, P.A. American Water Works Association, Denver, Co., 9-20
Venczel, L.V., Arrowood, M., Hurd, M. and Sobsey, M.D. (1997) Inactivation of Cryptosporidium parvum oocysts and Clostridium perfringens spores by a disinfectant and free chlorine. Applied and Environmental Microbiology 63, No. 4, 1598-1601.
Vesey, G,. Deere, D., Weir, C,. Ferrari, B., Gauci, M., Williams, K. and Veal, D. (1997) Optimising the use of monoclonal antibodies for the detection of Cryptosporidium in water samples. Proceedings of the Second Symposium on Health-Related Water Microbiology, University of Warwick. ed. Morris, R. and Gammie, A., 214-219.
Vesey, G., Deere, D., Dorsch, M., Veal, D., Williams, K. and Ashbolt, N (1997) Fluorescent In-situ labelling of viable Cryptosporidium parvum in water samples. 1997 International Symposium on Waterborne Cryptosporidium Proceedings, ed. Fricker, C.R., Clancy, J.L. and Rochelle, P.A. American Water Works Association, Denver, Co., 21-30.
Vesey, G., Deere, D., Weir, J.C., Ashbolt, N., Williams, K.L. and Veal, D.A., (1997), A simple method for evaluating Cryptosporidium -specific antibodies used in monitoring environmental water samples. Letters in Applied Microbiology 25, No.5, 316-320.
Wagner-Wiening, C., Kimmig, P. and Sacre, C., (1998) Epidemiological and methodological studies of Cryptosporidia in water samples Gas, Wasser, Abwasser 78, No.1, 37-41.
Walker, M.J., Walter, M.F. and Mcdonough, K. (1997) Large-volume samples for Cryptosporidium and Giardia from small streams. Journal of Environmental Engineering 123, No.1, 89-92.
Wallis, P.M., Erlandsen, S., Isaac-Renton, J.L., Olson, E., Robertson, W.J. and Van Keulen, H. (1996.) Prevalence of Giardia cysts and Cryptosporidium oocysts and characterisation of Giardia spp. isolated from drinking water in Canada. Applied and Environmental Microbiology 62, No.8, 2789-2797.
Wang, J., Rivas, G., Cai, X., Palecek, E., Nielson, P., Shiraishi, H., Dontha, N., Luo, D., Parrado, C., Chicharro, M., Farias, P.A.M., Valera, F.S., Grant, D.H., Ozsoz, M. and Flair, M.N. (1997) DNA electrochemical biosensors for environmental monitoring. A review. Analytica Chimica Acta 347, No.1Ú2, 1-8.
Watanabe, M E. (1996.) New Cryptosporidium testing methods. Environmental Science and Technology 30, No.12, 532A-535A.
Whitmore, T.N. (1997) Improved techniques for the recovery of Cryptosporidium from water. 1997
International Symposium on Waterborne Cryptosporidium Proceedings,
ed. Fricker, C.R., Clancy, J.L. and Rochelle, P.A. American Water Works Association, Denver, Co., 103-108.Wick, J.F. (1997) Detection of Cryptosporidium using strand displacement amplification and a colorimetric probe capture system. Abstract for the International Symposium on Cryptosporidium, Long Beach, California.
Wiedenmann, A., Rohn, S., Hauser, A.C. and Botzenhart, K. (1996) Transmission pathways for Cryptosporidium in Germany. GWF-Wasser/Abwasser 137, No.2, 105-108.
Wiedenmann, A., Steuer, S. KrŸger, P. and Botzenhart, K. (1997) A simple procedure for an extract evaluation of the selective detection of viable Cryptosporidium oocysts by PCR. 1997 International Symposium on Waterborne Cryptosporidium Proceedings, ed. Fricker, C.R., Clancy, J.L. and Rochelle, P.A. American Water Works Association, Denver, Co., 109-114.
Yates, R.S., Green, J.F., Liang, S., Merlo, R.P. and Deleon, R. (1997) Optimising coagulation/filtration processes for Cryptosporidium removal. 1997 International Symposium on Waterborne Cryptosporidium Proceedings, ed. Fricker, C.R., Clancy, J.L. and Rochelle, P.A. American Water Works Association, Denver, Co., 281-290.
Zuckerman, U., Gold, D., Shelef, G. and Armon, R. (1997) The presence of Giardia and Cryptosporidium in surface waters and effluents in Israel. Water Science and Technology 35, No. 11/12, 381-384.
[ Previous ] [ Contents ] [ Next ]
Drinking Water Inspectorate,
Floor 2/A1, Ashdown House,
123 Victoria Street,
London, SW1E 6DE
Telephone : 020 7944 5956
Facsimile : 020 7944 5969
E-mail: dwi_enquiries@detr.gov.uk
| A - Z Index | Business and Technical | Consumer Information | Contacting us |
| DWI Home Page | News | Product Approval | Search our site | Wales |
Drinking Water Inspectorate,
Floor 2/A1, Ashdown House, 123 Victoria Street, London, SW1E 6DE
Telephone : 020 7944 5956 - Facsimile : 020 7944 5969
E-mail: dwi_enquiries@detr.gov.uk
Updated 11 July 2001
Return to Publications and Reports Index
Return to Drinking Water Inspectorate Home Page
Department for Environment, Food & Rural Affairs (DEFRA)Home Page
The National Assembly for Wales / Cynulliad Cenedlaethol Cymru Home Page
Web site terms
© Crown copyright 2001