Is waterborne disease a myth?
Cryptosporidium makes headlines in Sydney
US litigation over Information Collection Rule
Workshop Report
The importance of infectious diseases as a major preventable cause of death, particularly in the developing world, is confirmed by the figures contained in the World Health Report 1996: Fighting disease, fostering development.
The report released by the World Health Organisation in May this year, estimated that of the 51.9 million worldwide deaths in 1995, about 17.3 million (33%) were due to infectious diseases. In this group of diseases, about 22% (3.75 million deaths) were due to food, water and soil borne agents. Diarrhoeal illnesses excluding cholera predominated with about 3.1 million deaths, followed by neonatal tetanus (459,000 deaths), hookworm (65,000 deaths) and roundworm infections (60,000 deaths). According to officially reported figures only 11,000 deaths were due to cholera, however the WHO estimates the true figure is about 120,000 deaths.
The report contained some important statements on the relevance of drinking water in the transmission of diarrhoeal diseases. For many years it has been widely accepted that contaminated water is the major vehicle for transmission, and this has led to a predominant emphasis on the microbiological quality of drinking water. However, more recent work by the WHO and others has shown that foodborne transmission is more important and probably accounts for 70% of diarrhoeal episodes. Bacterial contamination of weaning foods with pathogenic E. coli, Camplyobacter and Shigella is thought to cause up to half of all infant diarrhoeal episodes, and contributes heavily to infant mortality in developing countries.
These changes in thinking about the transmission of so-called "waterborne diseases" were explored in an article in the July 1996 issue of Water and Environment where writer RAJ Arthur discussed the World Health Report and the United Nations Habitat II conference with researcher Dr Sandy Cairncross of the London School of Hygeine and Tropical Medicine. Dr Cairncross has worked extensively in Africa in a WHO program to eliminate dranunculitis (Guinea worm disease). He pointed out that while waterborne transmission was clearly the cause of many epidemics of cholera and typhoid, sound epidemiological evidence was lacking to link water with other causative agents of diarrhoeal disease. This is particularly true of endemic diseases in developing nations.
It is now apparent that endemic transmission of enteric infections probably occurs mainly via contaminated food, hands, clothing and other household objects. The shortage of water for washing may have more impact on transmission than the microbiological quality of the water. In this context, there is increasing interest in the reuse of waste water for irrigation to release precious supplies of potable water for drinking and hygeine.
Simple intervention studies in developing countries have shown that diarrhoeal illness in communities can be greatly reduced by encouraging hand washing with soap before preparing meals and after defecation, indicating that basic hygeine and supply of sufficient quantities of water were important factors. Thus it appears that past emphasis on the microbiological quality of drinking water to the virtual exclusion of these other factors may have been inappropriate in public health programs.
The potential health threats of Cryptosporidium in Sydney's drinking water were the subject of a number of articles in the Sydney Morning Herald in October. The articles, by Science and Environment writer Bob Beale, comprised a page one feature on October 22nd and follow up articles on the 23rd and 24th October.
The stories were based on a draft version of report prepared for Sydney Water Corporation by its commercial research arm Australian Water Technologies (a member of the CRCWQT). The report was released to the Sydney Morning Herald by Sydney Water Corporation after a copy had been obtained by writer and consumer advocate John Archer under a Freedom of Information application. The draft report is undergoing peer review and the final version is expected to be delivered to Sydney Water in a few weeks.
The first article entitled "Deadly bug threat to tap water" outlined the results of an eight month monitoring program of Sydneys raw and finished water supplies undertaken in 1993 (prior to commissioning of filtration plants). Although Cryptosporidium oocysts were detected only once during this period, the concentration was high in the single positive sample (5,866 oocysts per 10 litres of raw water). The article also quoted a microbiologist as saying that studies suggest that even 1 oocyst may be sufficient to cause infection.
The next article on the topic "Bottled water may not protect against bug" noted that bottled water was not necessarily free of Cryptosporidium, depending on the source and the method of treatment before bottling. This piece also noted that many of the domestic water filters currently sold in Australia did not remove Cryptosporidium.
The report on 24th October focussed on the Potts Hill reservoir, a 800 million litre holding reservoir which serves the eastern side of Sydney. This uncovered reservoir is downstream of the Prospect filtration plant and thus presents an opportunity for recontamination of the filtered water prior to distribution. Although the reservoir has no fish, aquatic plants or other food sources for birds, it is sometimes used by water birds which may be a source of feacal contamination. The article did not state that Cryptosporidium species which infect birds have little if any ability to infect humans, although it is possible that oocysts of mammalian origin may survive passage through avian hosts if ingested.
It should be noted that the detection method used for these surveys did not allow determination of the viability of the oocysts, and if the proportion of viable oocysts was low the health risk would be substantially reduced. Also, the monoclonal antibody used to label oocysts prior to flow cytometry detection is known to crossreact with species other than C. parvum. Recent work (1) on commercially available immunofluorescence kits has shown that a "false positive" rate of up to 35% may occur with Cryptosporidium oocysts which are not C. parvum. Of the several recognised species of Cryptosporidium only C. parvum is considered to constitute a risk to human health.
The AWT researchers used spiking experiments to compare 3 different methods of recovering Cryptosporidium oocysts and Giardia cysts from water samples, and concluded that the ASTM P229 protocol gave the poorest results for both test organisms. The tests on water samples from the Sydney water supply system were therefore carried out using a calcium flocculation - centrifugation procedure followed by immunofluorescence flow cytometry. The spiking tests indicated the recovery yield of this process was up to 30x more efficient than the ASTM method which has been used in most published studies, therefore it is difficult to compare the oocyst/cyst numbers detected by the two different techniques.
The human volunteer experiments conducted by Dupont et al.(2) tend to suggest that infection from a single oocyst would be a rare event - of 5 volunteers who ingested 30 viable C. parvum oocysts, only 1 became infected and this person did not actually develop symptoms.
There is justifiable concern over the threat of Cryptosporidium infection in immuno-compromised persons, however it should be noted that immune status does not appear to significantly influence the risk of infection but rather affects the outcome of infection. Data from waterborne outbreaks of cryptosporidiosis indicate that immunocompromised people (people with HIV/AIDS, those receiving cancer therapy, organ and bone marrow transplant recipients, people with congenital immune deficiencies) are not at increased risk of acquiring cryptosporidiosis but are at greater risk of suffering prolonged and severe infection (3).
These articles highlight the difficulties of water authorities and health departments worldwide in dealing with public concern over the health risks of Cryptosporidium in drinking water. While documented outbreaks in a number of cities overseas clearly demonstrate significant health risks when major contamination occurs, current detection methods lack both the sensitivity and specificity to allow clear assessment of risks in nonoutbreak situations. To assess risks to public health we need to know not merely "is there Cryptosporidium in the water?" but "is it Cryptosporidium parvum? and is it viable?" Hopefully new detection methods under development in Australia and elsewhere will soon allow these questions to be answered.
1 Evaluation of a commercial enzyme immunoassay (EIA) and immunofluorescent antibody (IFA) test kits for the detection of Cryptosporidium oocysts of species other than Cryptosporidium parvum. Graczyk, TK, Cranfield MR and Fayer R (1996). Am J Trop-Med-Hyg 54 p274-279. (Summarised in this issue - see From the Literature section).
2 The infectivity of Cryptosporidium parvum in healthy volunteers. DuPont HL, Chappell CL, Sterling CR, Okhuysen PC, Rose JB and Jakubowski W. New-Eng-J-Med (1996) 332 p855-59.
3 Assessing the public health risk associated with waterborne cryptosporidiosis: report of a workshop. Morbidity and Mortality Weekly Report, June 1995, 44 No. RR-6, Centres for Disease Control.
It was reported in the October 7th edition of Environment Week that continuing court action against the US EPA by the American Water Works Association may delay the development of rules to limit disinfection byproducts and microbial contaminants.
The AWWA has taken federal court action against the EPA over the Information Collection Rule which was issued on May 14th. The ICR compels water authorities to collect and report data on microbial and disinfection byproduct levels in water from early 1997. It is intended that this data will provide the basis for formulating future drinking water regulations in the US.
The AWWA action particularly focuses on the limitations of the ICR methods for the detection and identification of protozoa in water. The prescribed method for detection of Cryptosporidium (immunofluorescence by ASTM P229 protocol) can give false positive results and cannot distinguish betwen viable and inviable oocysts. An evaluation of the accuracy of 12 commercial testing laboratories using blinded spiked samples showed serious deficiences in a number of aspects (1). Four laboratories incorrectly identified algal cells as protozoa (false positives), four failed to detect Giardia and 6 failed to detect Cryptosporidium (false negatives). Only 2 laboratories correctly identified both types of protozoa and did not misclassify the algal cells. The standard and detail of written reports of the test results also varied greatly between laboratories.
The AWWA believes that data collected by this technique will inevitably be flawed, and cannot be legitimately used to develop regulations. There is also concern among water authorities that the compulsory public reporting required by the ICR will leave them open to legal action by consumers, even when the scientific evidence of risk to health is uncertain.
The AWWA action also challenges the short time interval provided to implement the required testing programs, and the addition of some testing requirements in the final form of the ICR which were not present in the proposed version on which consultation with stakeholders was based.
The EPA has stated that the litigation may inhibit ICR negotiations between the EPA and the water industry, however the AWWA has countered that it had no choice but to bring action within the mandatory 45 day period allowed after the ICR was promulgated, to protect the rights of the water utilities to dispute the ICR provisions.
1 Clancy JL, Gollnitz WD and Tabib Z. Commercial labs: how accurate are they? Journal of the AWWA, (1994) Vol 86 (5) p89-97.
Workshop on Micro & Ultrafiltration in Water Treatment, Friday 18 October, Melbourne.
The workshop was held at the CSIRO Division of Chemicals and Polymers, Clayton and was attended by approximately 30 people. The presenters had a variety of expertise ranging from researchers to manufacturers and water service providers.
The workshop began with a welcome by Don Bursill (Director, CRCWQT) and an introduction by Tony Priestley (CSIRO Division of Chemicals and Polymers, Deputy Director CRCWQT). The aim of the workshop was to gain more knowledge of Micro and Ultrafiltration and to formulate a draft program of relevant research projects that could be undertaken by the CRC for Water Quality and Treatment.
A technical overview was given by Tony Fane (University of NSW). Tony examined membrane types and listed some strategies and future potential for improvement. He considered applications of membranes which included membrane use in: the desalination process, secondary treatment, the removal of industrial effluents and the reuse of water. Virus removal using Microfiltration and the variables involved such as pressure, bacteria layer and time were covered. Hybrid systems using a membrane plus a biological or chemical process were discussed.
The next section of the workshop consisted of a series of presentations from membrane filtration users and manufacturers. The first speaker was Pierre Alla (Australian Water Services) who discussed the aims and interests of AWS which include providing cost efficient water of the best quality and using the best combination of treatment processes. He also described AWS interest in reuse of waste water and combined systems.
Dharma Dharmabalan from Barwon Water spoke about Microfiltration at the Meredith Water Treatment Plant. He gave an overview of the plant which has a capacity of 2.5ML/day with further expansion possible, and currently provides for several country communities. He reviewed the strengths and weaknesses of the filtration processes. Strengths included: more compact, lower capital cost, absence of clarifiers, no sandfilters, automatic operations, good particle removal (Giardia and Cryptosporidium), reduced chemical costs (for low colour water) and changes in flow rates do not affect final water quality. Weaknesses included: colour removal-inability without chemicals, poor dissolved compounds removal, problems with disposal of washwater and reject cleaning solution, short filter run times and high volume of washwater, fairly high energy costs, specialist skills needed to trouble shoot problem areas.
The problems of operation and maintenance were highlighted, in particular the increased membrane fouling rate and frequency of chemical cleaning, colour removal targets being hard to meet, the biological instability of the water, no by-pass option during maintenance and retrieval of data for analysis when problems occur. Future work and issues were discussed with suggestions such as the need for pre/post treatment to enhance water quality, installation of dynamic membranes and use of gas for backwashes.
Colin Nash from Memtec provided a manufacturers point of view. He presented Memtec's research and development targets in which the following points were raised: membrane and membrane systems cost reduction, colour and Total Organic Carbon (TOC) removal with Microfiltration, better understanding of fouling mechanisms and optimising chemical cleaning methods. The strengths and weaknesses of membrane filtration were reviewed. He presented his 'Dream Membrane' - this is an ideal membrane which is non fouling, has a TOC and toxin removal capacity of Nanofiltration, requires no pretreatment, works at Microfiltration differential pressures (ie < 100k pa) and has a sustainable flux rate of >200 L/hr/m on cold water. As our knowledge of membrane technology increases this "dream membrane" or aspects of it may be possible in the future.
The last speaker in this section was Pradeep Kumar from the NSW Department of Land and Water Conservation. He presented another users viewpoint. Pradeep reviewed the Microfiltration plant at Kangaroo Valley which has a capacity of 0.84 ML/d and has been operational since December 1993. Some features he highlighted about the plant were: the plant reduces turbidity very effectively, it cannot reduce true colour consistently, dissolved iron and manganese cannot be removed without preoxidation, dissolved organic compounds are not effectively removed, faecal coliforms, coliforms and E. coli are effectively removed, recycling of poor quality lagoon supernatant can deteriorate the membrane performance, trans-membrane pressure is unusually high and filtration capacity is now significantly reduced from design specifications. Future strategies were considered for the plant in regard to algal toxin removal, taste and odour control, dissolved organic compound removal, number of backwashes, CIP (Clean In Place) cycles and membrane life and costs of operation and maintenance.
The second half of the day was aimed at considering future research topics. Mary Drikas (AWQC) talked about membrane evaluation for pathogen, organics and toxin removal. Mary discussed research into algal and algagenic products comparing polyvinylidene fluoride Microfiltration membranes with 0.3 µm pores and polyether sulfone Ultrafiltration membranes. The parameters that were investigated were permeate flux, total cell numbers before and after filtration, chlorophyll a and microcystin-LR levels.
Tony Priestley reviewed hybrid systems with coagulation and adsorption. He summarised the performance of Nanofiltration, Ultrafiltration and Microfiltration and their ability to removal dissolved organics. Ways of converting soluble materials into a particulate form were discussed, approaches including: coagulation with a metal salt, precipitation with a cationic polymer, absorbing with or without a polymer aid on clay or metal oxide and absorbing on powered activated carbon or a finely divided ion-exchange resin.
Tony Fane and Hans Griesser (CSIRO Division of Chemicals and Polymers) concluded the days presentations with a discussion about new membranes and minimising fouling and maximising performance. Tony described what is needed to achieve better system performance including: improved membranes and modules and the optimisation of operating conditions and cleaning strategies. Hans Griesser spoke about his research into membrane fouling with regard to contact lenses and the surface interactions involved. The principals involved here can be related to membrane filtration.
The day concluded with a general discussion of research topics. Suggestions for research included: looking at the causes of membrane fouling, the removal of natural organic matter, hybrid systems and evaluation of some current membrane filtration systems. It was resolved there should be further discussion by CRCWQT partners involved in future research.
The Placebo Effect
The word placebo appears in the Bible in Psalm 116, Verse 9, "placebo domino in regione vivorum" which is translated from the Latin "as I please". The concept of the placebo and the placebo effect in medicine was first formally discussed in 1945 by Pepper - A Note on Placebo (1).
A placebo treatment usually consists of a "dummy" medication or intervention. This intervention can range from the trial participant taking a tablet, to answering a questionnaire, to using a sham water filter (as will be used in the Water Filter Study). The importance of the placebo effect was described by Beecher who reviewed fifteen studies of placebo use in patients suffering a variety of conditions (cited in 2). Amongst the problems studied were pain after surgery, headache, drug induced mood change, seasickness and the common cold. On average, these symptoms were "satisfactorily relieved" by a placebo treatment in 35% of patients (the range being 15% to 58%) (2, 3).
A wide variation in response is not uncommon with placebos. The placebo response can be seen in patients with acute and chronic conditions, its effect can continue after the cessation of "treatment" and a dose response effect can sometimes be seen. Two placebo capsules can have a greater affect on relieving pain than one alone4, 1. The participants perception of the characteristic of the drug preparation can also influence their response. Larger capsules tend to be perceived as stronger, yellow capsules tend to be thought of as stimulants, injections may produce larger effects than do pills (4, 5, 2).
The placebo effect is not only seen with medications. Sham surgery and interventions such as sham tooth grinding procedure and sham ultrasonic treatments have also been shown to have a placebo effect (2).
Placebos have also been associated with side effects such as nausea, drowsiness and headaches. The overall incidence of adverse events in healthy volunteers during placebo administration was 19%. Placebos may also make pre-existing symptoms worse (4, 2).
The participants expectations of the likely success of the treatment or intervention can influence their response, as can their general attitude towards the treatment and the treatment provider, be this attitude positive or negative. This attitude and expectation can make the placebo response greater or it can reduce the response (2).
The potential of the placebo effect in a randomised trial is such that it may distort the answer if the participant or those responsible for treatment know what intervention or treatment the person is receiving. This problem can be avoided by making the trial double blind, whereby neither the participant, nor the researcher are aware of what intervention or treatment the participant receives. This removes a potential bias in the study.
For the placebo to be effective in removing participant and observer bias (both conscious and subconscious) it should simulate the true intervention as closely as possible but must not treat the medical condition or alter the status quo.
When measuring the response of an intervention at the end of the study, we generally assess the placebo response and the response of those who received the real intervention, describing the "true response" as the difference between these two groups. Before we assess the placebo effect in a study, factors potentially influencing the placebo effect such as the natural course of an illness, regression towards the mean and unidentified parallel interventions must be considered. These factors can lessen or increase a placebo effect and should be taken into consideration when estimating ing the placebo effect and assessing the actual effect of the real treatment or intervention (6).
1. Rosenzweig P, Brohier S, Zipfel A. The placebo effect in healthy volunteers: Influence of experimental conditions on the adverse events provirtual during phase I studies. Pharmacol Ther 1993;54:578-83.
2. Turner JA, Deyo RA, Loeser JD, Von Korff M, Fordyce WF. The importance of placebo effects in pain treatment and research. JAMA 1994;271(20):1609-14.
3. Fisher RW. Comparison of antipruritic agents administered orally: a double-blind study. JAMA 1968;203(6):130-1.
4. Blackwell B, Bloomfield SS, Buncher CR. Demonstration to medical students of placebo responses and non-drug factors. Lancet 1972;1(June 10):1279-82.
5. Buckalew LW, Coffield KE. An investigation of drug expectancy as a function of capsule color and size and preparation form. J Clin Psychopharm 1982;2(4):245-8.
6. Ernst E, Resch KL. Concept of true and perceived placebo effects. BMJ 1995;311:551-3.
We continue our series of mini-CVs on people working in Program 1 of the CRCWQT.
Dr Margaret Hellard
Margaret Hellard holds a CRCWQT PhD Research Scholarship with the Department of Epidemiology and Preventive Medicine, Monash University. Prior to this appointment she gained her medical qualifications at Monash University and trained as an infectious diseases physician in Melbourne.
Margaret then worked for the Communicable Diseases Unit of the World Health Organisation in Geneva before returning to Melbourne. She has also worked as a part time Lecturer at DEPM and undertaken research on the assessment of microbiological risks associated with drinking water. Her current research interests are the Water Filter Study, community gastroenteritis and multiresistant organisms in a hospital setting.
Ms Andrea Hinwood
Andrea Hinwood holds a Masters degree in Applied Science from RMIT, and worked with the Victorian EPA prior to taking up PhD studies at DEPM. Her research work centres on the human health impact of environmental arsenic contamination. In 1995 Andrea carried out a pilot study to trial recruitment, sampling and analysis methodologies to be utilised in a larger study of arsenic exposure and absorption. The main study is now underway, with the fieldwork phase and sample collection expected to be completed by late 1997.
During her PhD canditure Andrea chaired the Technical Options Committee on Aerosols, Sterilants, Miscellaneous uses and CTC for the United Nations Environment Programme on reduction of Ozone Depleting Substances, and was a member of the Technology and Economic Options Committee.
Dr Wayne Smith
Wayne Smith received his medical degree from Newcastle University, and the degree of Master of Public Health from the University of Sydney. After clinical experience in a number of Sydney hospitals, Wayne worked in the NSW Health Department as a Public Health Officer in the Epidemiology Branch, and later as an NHMRC/PHRDC Research Fellow in the Department of Community Medicine at Westmead Hospital.
Wayne took up his present position as Fellow in Epidemiology at NCEPH in 1995, and has worked on a number of projects including asthma and air pollution, population survey methods, the Blue Mountain Eye Study, palliative care, and accident prevention in the elderly. Wayne is also Course convenor of the Graduate Diploma/Master in Population Health program.
Ms Elisa Bastone
Elisa Bastone was recently awarded her Masters degree in Applied Microbiology from RMIT. Her research studies in the Department of Clinical Pharmacology at the Alfred Hospital, included the development and use of dynamic in-vitro models and clinical trials to determine the efficacy and safety of high dose aminoglycoside antibiotic therapy.
In her present position as Research Fellow in DEPM she is primarily involved with the EnvAs study, which aims to determine the absorption and health impact of arsenic from environmental sources in rural Victoria. For the last few months Elisa has been busy recruiting participants for the study, and collecting biological and environmental samples for arsenic analysis.
Ms Pam Lightbody
Pam Lightbody completed a Science Degree at Monash University majoring in Environmental Science in 1990 and a Certificate in Office Practices in 1994. She has worked as a "Person Friday" for an accounting firm and as a Seminar Coordinator for a computer magazine since leaving university.
Pam began her work at DEPM as a part-time Research Assistant on the Healthwise Study (a major occupational health study for Alcoa Australia). In mid-1996 she began working fulltime on CRCWQT projects at DEPM. Pam maintains the literature collection and database for the water research group, provides research support for a number of projects and is Assistant Editor for the Health Stream Newsletter.
Dr Alex Padiglione
Alex Padiglione is an Infectious Diseases Physician, currently employed as a lecturer at the Department of Epidemiology and Preventive Medicine at Monash University. He graduated with Honours in Medicine at Monash University in 1986, and has spent most of the last decade working in clinical medicine at both the Alfred and Fairfield hospitals, during which time his research interests have included areas in HIV medicine and tropical diseases.
Alex's current research interests include pneumococcal pneumonia, travel medicine and community gastroenteritis. As part of the CRC for Water Quality and Treatment he is working on the project " The early detection of outbreaks of waterborne gastroenteritis - feasibility study".
Management Committee Meeting
The next meeting of the Management Committee of the CRCWQT will
take place on Wednesday 29th January 1997 in Adelaide. Venue
to be confirmed.
Change of date notified 23/12/96 - Management Committee meeting will be held on Tuesday 28th January. Venue - University of Adelaide.
Board of Management
The next meeting of the Board of Management of the CRCWQT will
take place on 3rd March 1997 in Sydney. The meeting will be held
at the Prospect Water Filtration Plant, and will be hosted by
AWS.
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