This project is a collaboration between CMPS&F, Melbourne Water and Monash University. Other CRCWQT members will be involved as expert reviewers.
Cryptosporidium and Campylobacter are found in raw water sources throughout Australia. There is no evidence that this normally results in significant illness but there is growing concern amongst water authorities about the absence of clear guidelines on interpreting and responding to these results. Development of such guidelines awaits knowledge regarding the relationship between monitoring results and disease incidence in the consumer population. However, risk modelling approaches are being increasingly applied overseas as part of the decision making process for setting guidelines in these countries. This may in turn have an effect on the water quality guidelines for Australia.
This project aims to develop an authoritative position on the value of such modelling approaches and on the interpretation of monitoring results and appropriate responses. The work will be carried out within the framework of water quality management applicable to Australian water authorities and will build on similar projects already completed.
The project will proceed as a series of clearly defined stages, summarised below. A group of CRCWQT personnel will review the project at every stage with additional reviewers being sought at some of the stages. Each stage will involve the production of a draft report that will be modified taking on board the comments made by the reviewers. This peer review will form an integral part of the project and is essential to its success.
Project Timetable
Applications
The system analysis will have a number of applications both in directing future research and in water system management. These can be summarised as follows:
Before these Canadian studies, waterborne gastroenteritis in developed nations was considered to be restricted to epidemic situations where a specific contamination event or treatment failure had occurred. However the outcomes of the randomised (but unblinded trials) by Payment and co-workers have suggested that a measurable fraction of endemic gastrointestinal disease may be arising from drinking water that meets current standards.
In this new paper Schwartz et al. present evidence that rises in rates of gastroenteritis in children were preceded by rises in turbidity of the treated drinking water supply. The authors looked for correlations between the number of children attending the emergency department at the Children’s Hospital of Philadelphia (CHOP) for gastroenteritis with the turbidity of treated water in the preceding 14 days. The paper also received coverage in the 4th November issue of the New York Times newspaper.
The 1.2 million people of Philadelphia receive their drinking water through three treatment plants that derive their water supply from the Schuylkill and Delaware rivers. The water from the rivers is considered to be “highly contaminated”. The water at each treatment plant is pre-chlorinated, receives conventional water treatment (flocculation and sedimentation), then filtration and leaves the plant with a chloramine residual.
The study looked at children attending the emergency department with gastroenteritis as defined by the International Classification of Diseases code (ICD-9). A statistical model was then used to determine if rises in attendances to emergency at CHOP were preceded by rises in turbidity. This statistical model took into account other factors that might influence the number of cases of gastroenteritis such as the daily temperature, seasonal variations, long-term trends, temperature and day of the week. Turbidity levels between 1 and 14 days before the hospital attendance were considered.
The turbidity of the treated water was measured in accordance with the requirements of the Safe Drinking Water Act 1989 (the number of measurements each day was not stated in the paper), and the authors obtained information on the minimum, maximum and mean readings daily readings from the 3 plants from the Philadelphia Water Department. The average turbidity for the whole city on each day was taken as the arithmetic average of the mean reading for each plant. The 10th and 90th percentile of turbidity readings for the treated water were 0.14 and 0.22 NTU respectively.
Complex statistical methods were used to analyse the data based on Poisson regression analysis but including a moving regression smoother (to remove long term patterns from the data) and regression splines (to remove short term trends). Robust regression was also used to avoid the risk of results being heavily influenced by extreme observations (Editor’s note - if you don’t understand any of this, you’re not alone!). The authors also divided the observations by age (0 to less than 3 years old vs 3 years and over) , and by residential zip code to correspond to the 3 water supply areas, and conducted separate analyses for each group.
There were 3,282 attendances for gastroenteritis between July 1 1992 and December 31 1993. Turbidity levels 4 days and 10 days before were statistically significantly associated with rises in gastroenteritis. Attendances at the emergency department rose by between 7.2 and 6.7 percent for every interquartile increase in turbidity (0.04 NTU).
When the age groups were analysed separately, the 4 day lag was significantly associated with attendance rate in the 3 years and over group, but not in the less than 3 year olds. Conversely, hospital attendance in those under 3 years of age was significantly associated with a 10 day lag period after increases in turbidity, but not with a 4 day lag. The authors also looked at admissions to hospital for gastroenteritis, (a less frequent event than emergency attendances) and found that there was a significant rise in admissions 8 days after the turbidity rose.
The authors comment that the lag times between turbidity rises and increases in hospital attendance for gastrointestinal illness are plausible for the incubation periods of known waterborne pathogens such as viruses (1-5 days) and giardiasis (2 - 14 days).
What does this study mean?
This new study adds another intriguing observation to the complex issue of waterborne disease, however it is worthwhile pointing out some of the limitations in the conclusions that may be drawn from it. Firstly, as in all observational studies the “exposure” to the factor under investigation (turbidity) was not controlled in any way, the investigators simply made use of existing data from water company and hospital records and drew the inference that exposure to changes in turbidity was the cause of the changes in attendance rates at the hospital. This is an important point and essentially this means there may have been other factors that caused rises in rates of gastroenteritis attendances at the same time as the turbidity increased. In the study Schwartz et al. took some of the known factors into consideration in the analysis (eg day of the week, temperature) but there may be factors that they did not know about or measure.
The rates of gastroenteritis attendances were only presented for lag times of 4 and 10 days. However 12 other days (ie 1,2,3,5 days etc) were considered in the analysis so it would have been helpful to have had this data presented, although understandably space constraints may have prevented this. Health Stream has contacted the authors to request this information and will present it in the next edition of Health Stream if we receive permission to do so. It would be expected that if rises in turbidity are truly the cause of rises in gastroenteritis attendances then the reverse should also be true.
In the Discussion section of the paper the authors comment on possible sources of error such as misclassification of the diagnosis (error rates of up to 20% have been found in some studies of hospital coding), and dates of exposure (no attempt was made to allow for different lag times before water reached consumers). No information is presented on the degree of error which may be associated with the turbidity readings, and the use of an arithmetic mean to calculate the “average” turbidity in the city each day is a little puzzling given that the 3 plants supply 55%, 28% and 17% respectively of the water supply by volume.
Subsequent to the investigation of the main Milwaukee outbreak, Morris et al. carried out an analysis of hospital records and water turbidity readings over a period of 16 months before the recognised outbreak. They found that attendance of children with gastrointestinal illness at hospital emergency departments showed a strong correlation with rises and falls in turbidity, but did not describe any specific time lag relationships(2).
The New York Times article on this study included a comment from Dr WR MacKenzie - one of the principal investigators of the 1993 Milwaukee Cryptosporidium outbreak. Dr MacKenzie commented that while he found the Philadelphia study “intriguing and concerning” he did not feel that the results of “one study at one hospital and one city with several different water supplies” was an adequate basis for changing water regulations.
Source Water vs Distribution System?
The Schwartz et al. Epidemiology paper was accompanied by an editorial entitled “Defining Safe Drinking Water” by Eduardo Franco(3), a member of the research group which carried out the Canadian studies of endemic gastroenteritis. This article outlines the commonly accepted definition of safe drinking water in terms of turbidity and chlorine treatment, then describes the results of the two randomised trials conducted in Montreal.
The author contends the results of these studies demonstrate that a substantial proportion of gastrointestinal disease (up to 50%) is attributable to microorganisms in drinking water, and this represents a large and preventable cost and morbidity burden on society. The findings of the Philadelphia study are seen as further supporting evidence and the author considers that they will play an important role in influencing more stringent water quality standards.
However the findings of Schwartz et al. do not appear to mesh with the interpretation of the Canadian group. From their own results they have concluded that the fraction of gastrointestinal illness attributable to drinking water arises from microbiological events in the distribution system, as the rate of illness was the same in a group drinking bottled plant water (that did not pass through the distribution system) as it was in the group receiving bottled reverse osmosis filtered water(4). In contrast the observations by Schwartz suggest that variations in rates of illness are due to changes in the numbers of pathogens (carried in or on small suspended particles) coming through the distribution system from the treatment plant.
(1) Drinking water turbidity and pediatric hospital use for gastrointestinal illness in Philadelphia. Schwartz J, Lavin R and Hodge K (1997) Epidemiology 8 (6) p615-620.
(2) Temporal variation in drinking water turbidity and diagnosed gastroenteritis in Milwaukee. Morris RD, Naumova EN, Levin R and Munasinghe RL. (1996) American Journal of Public Health 86(2) p237-239.
(3) Defining Safe Drinking Water. Franco EL (1997) Epidemiology 8 (6) p607-609.
(4) A prospective epidemiological study of gastro-intestinal health effects due to the consumption of drinking water. Payment P, Siemiatycki J, Richardson L, Renaud G, Franco E, Prevost M. (1997) Int. Journal of Environmental Health Research 7 p5-31.
This type of protein has been studied in other protozoan parasites, and is believed to play an important role in attachment of the parasite to the host cell surface. Therefore it is hypothesised that changes in the gene sequence which lead to changes in protein structure might affect the specificity of attachment and thus the host range of the parasite.
DNA was isolated from each of the oocyst preparations and a 369 base pair region of the gene was amplified by polymerase chain reaction. The segment of DNA was then purified and the DNA sequence was determined. The infectivity of some of the oocyst preparations was tested by administering approximately 106 oocysts to 2 day old calves and/or 4-6 day old mice. The animals stools were collected daily from day 5 after infection and examined by light microscopy or immunofluorescent flow cytometry for the presence of oocysts.
Computer analysis of the DNA sequences showed that isolates could be classified into 2 primary genotypes which differed at 5 nucleotide base positions. The genotype 1 group comprised 13 isolates from human cryptosporidiosis outbreaks, while the genotype 2 group consisted of 3 human and 24 isolates. The number of isolates tested for infectivity is not entirely clear from the paper, however none of the tested genotype 1 isolates could infect calves or mice, while the genotype 2 isolates successfully infected the test animals. One isolate from genotype 1 was tested in a neonatal pig, establishing a brief moderate infection. Two genotype 1 isolates were tested for ability to infect human cell cultures and both established successful infections.
The authors conclude that these observations support the existence of two distinct cycles of transmission for Cryptosporidium parvum - one from human to human, and one cycling between humans and cattle. For two of the three human isolates of genotype 2 examined here, a clear link to cattle was evident from epidemiological investigations. The third isolate came from a waterborne outbreak where the source of contamination was unknown but cattle were present in the watershed at the time the water became contaminated. The genotype 1 isolates came from five different outbreaks. Epidemiological investigations had implicated drinking water in two of these outbreaks, recreational water in one, person to person transmission in one, and for the last no source was identified.
The presence of two genetically distinct classes among C parvum isolates has been previously suggested by comparison of enzyme polymorphism patterns, DNA sequences (of unknown function) and ribosomal RNA genes, however this is the first evidence clearly linking the genetic differences to host specificity and providing an explanation of the functional basis for the differences in host range.
Interestingly, four of the isolates characterised here originated from the 1993 Milwaukee outbreak - three were isolated at the time of the outbreak and the fourth was isolated in 1996 from an AIDS patient with chronic infection who was originally infected in the outbreak. All belonged to genotype 1, causing some people to conclude the world’s largest recorded outbreak of waterborne disease was due to human sewage contamination (see below).
(1) Genetic polymorphism among Cryptosporidium parvum isolates: evidence of two distinct human transmission cycles. Peng MM, Xiao L, Freeman AR, Arrowood MJ, Escalante AA, Weltman AC, Ong CSL, MacKenzie WR, Lal AA and Beard CB (1997) Emerging Infectious Diseases 3 (4) p567-573.
Cattle innocent at Milwaukee?
The data reported in the paper described above have sparked some controversy over the cause of the 1993 Milwaukee outbreak where an estimated 403,000 people were affected by Cryptosporidium contamination of the water supply. The 18th October edition of the Milwaukee Journal-Sentinel newspaper reported that a parasite disease expert from the Centres for Disease Control said the new evidence ”strongly indicates” the outbreak was due to human faecal material in Lake Michigan. This was picked up by members of the ProMED email discussion list who contacted the author of the original paper describing the Milwaukee outbreak, Dr William R MacKenzie at CDC (also an author on the above paper) for his comments.
Dr MacKenzie’s reply emphasised that at the time of the investigation, a number of potential sources were considered including cattle farms along the river, slaughterhouses and human sewage, but there was no evidence to implicate any one source above the others. Even considering the recent genotyping work on these isolates, Dr MacKenzie still believes it is premature to conclude the contamination source was human since only a few isolates have been examined.
This year’s ASM conference was dubbed “A Festival of Microbes” to mark its association with the Festival City - Adelaide. With over 3,500 members, the ASM is the largest Australian society in the biological field, and about 1,000 registrants attended the conference at the Adelaide Convention Centre. This report highlights a few of the sessions on water-related topics.
Microbes and Pollutants Anne Glover from the University of Aberdeen, Scotland described the development of bioluminescent Pseudomonas strains to provide a sensitive method of continuously monitoring pollution by biologically available compounds in both water and soil environments. Pollutants which cause metabolic inhibition of the cell lead to a rapid decrease in the luminous product which can be easily monitored. One bioluminescence system is already on the market but its use is limited to marine waters in a fairly narrow pH range. Work on a non-specific sensor system is well advanced and the research is now aiming at specific sensors by linking specific promoter genes to the lux gene system.
Ken Timmis from the National Centre for Biotechnology, Germany spoke about the use of Pseudomonas strains for removal of mercury from waste water and soil. By fixing the genetically engineered bacterial cells in a column and passing an aqueous waste stream through, the elemental mercury can be recovered by volatilisation or activated charcoal. The performance of the system with industrial wastes is less efficient than in laboratory tests (possibly due to the presence of inhibitory compounds), however the results are still promising and a pilot scale plant is now being built in the Czech Republic.
Cyanobacteria and their toxins Ian Falconer of the CRCWQT / University of Adelaide gave an overview of the problem of cyanobacterial contamination of water supplies, including how his own interest arose from a personal experience of water contamination of the laboratory drinking water supply in Armidale, NSW. Reports of acute human toxicity in Australia seem to be limited to the Palm Island incident where 140 children in a mostly Aboriginal community were affected but all recovered after drinking water contaminated with Cylindospermopsis toxin. However in Brazil 55 deaths among 130 dialysis patients occurred when the water supply used for dialysis became contaminated and the water purification system was not adequate to remove the toxins.
Cyanobacterial blooms have had significant economic effects in Australia - the Gippsland Lakes area in Victoria suffered a major drop in tourism due to closure of contaminated lakes for recreational use, and in WA about $80 million has been spent building a seawater channel to flush Nodularin blooms from a recreational water estuary. In 1991 several major blooms along the Darling River required emergency deployment of portable water treatment plants by the Army to provide drinking water to townships, and Cylindrospermopsin blooms in 2 major water storages in Brisbane have caused restrictions to be imposed on water use, fishing and recreation.
George Ganf of the University of Adelaide described the similarities and differences between bloom forming cyanobacteria and eukaryotic planktonic microalgae which occur in similar environments. Studies on the effect of nutrients and light on growth have shown that the cell yield is limited by nutrient availability (mainly phosphate and nitrogen) but growth rate is limited by light intensity. Bouyancy appears to be regulated by variations in the size of gas vesicles (increasing size lightens the cell) and carbohydrate reserves (increasing amounts make the cell more dense). The general pattern appears to be that cells rise at night, build up carbohydrate reserves by photosynthesis during the day, then sink again. For small clumps of cells (up to 10 µm in diameter) the amplitude of movement may only be about 10cm, however large clumps (up to 250 µm in diameter) may oscillate through 4 to 5 metres.
Recent findings suggest that contrary to previous beliefs, the occurrence of blooms does not represent a sudden growth increase of cyanobacteria, but rather a redistribution of an existing population under the influence of environmental conditions. A complex interaction of nutrient levels, light and wind conditions determines which species predominate in a given water body and whether the cells remain dispersed or form a shoreline scum (bloom).
Mike Burch of the CRCWQT spoke about his studies on bloom formation by Anabaena species along part of the Murray River. In contrast to common perception, the nutrient conditions in the river channel are not favourable for cyanobacterial growth with doubling times in the order of 5 to 18 days being observed (as opposed to 15 - 21 hours by the same species under ideal laboratory conditions). Supplementation experiments suggest that nitrogen availability was the main limiting factor.
Conditions in the wetlands and lagoons are more favourable, and it appears that cyanobacterial numbers may build up here then enter the river channel depending on a combination of water flow and wind conditions. Once in the river it appears that blooms will form only when a specific set of environmental conditions occur - low flow rates in the summer and autumn combined with low wind speeds (less than 3 km /hour) over a prolonged period produce a persistent thermal stratification which leads to bloom formation. Another potential contributory factor which has not been studied is the characteristics of the microfauna such as Daphnia that consume cyanobacteria. If the microfauna numbers are being reduced by the effect of pesticides, this may also favour increased cyanobacterial growth.
Renata Velzeboer from the CRCWQT summarised work carried out since 1990 on cyanobacterial blooms in the Murray Darling basin. Anabaena species were the most commonly found types in river water, while Microcystis predominated in standing waters (lakes, dams) and Nodularia in brackish waters near the mouth of the Murray river. Of 231 samples analysed, 133 were non-toxic, 56 contained neurotoxins and 42 contained hepatotoxins. This rate of about 42% of blooms being toxic is similar to most overseas surveys. The toxin content of blooms varies over time and field studies have shown that blooms which are initially non-toxic may start to produce toxin later in their life cycle.
Water Microbiology Jim Ralph from Flinders University spoke about using analysis of faecal sterols in water samples to determine the sources of faecal pollution. The provirtual of faecal sterols is highly characteristic for each species, however there was doubt whether individual species contributing to faecal pollution could be identified from natural water samples. Water and sediment samples taken from 12 sites along the Torrens river in Adelaide (where total coliform levels are often more than 10,000 /100ml) were analysed in triplicate for their sterol content. 11/12 water samples had very low sterol levels, the remaining water sample (from near a stormwater inflow) had sterols suggestive of faecal pollution from dogs. The sediment samples had higher sterol levels and matched the expected provirtuals for water birds. One site (confirmed by a member of the audience to be a swan breeding area) had a high level of sterols specific for swans. There was no evidence of human faecal pollution (which would be expected to be marked by high levels of coprostanol).
Christine Kaucner from Water Ecoscience described the use of the “Diamond” filter for the concentration of protozoa from water. This negatively charged glass wound depth filter has been previously used for virus concentration where the electrostatic charge binds the virus particles. Experiments at WES have shown it also provides a reliable and efficient means of concentrating protozoa. The filters are relatively cheap and can be used on-site to avoid transporting large sample volumes to the lab. DAPI/PI viability staining has shown no drop in viability after filtration and recovery, in contrary to published data on the conventional chemical flocculation technique.
Chris Saint from the CRCWQT spoke about his work on improving detection of Legionella using the Enviroamp commercial kit. The current kit used per instructions provides a rapid method of detection, the convenience of prepackaged reagents, internal controls, a 12 month shelf life and minimal equipment requirement. However the technique is costly as all samples need to be put through the entire test procedure, it does not detect viability, false positives can occur from the primer, and environmental samples can inhibit the PCR reaction. Chris has been able to modify the method by growing the bacteria for 3-10 days on a plate, then carrying out capillary PCR with 1/2 quantities of reagents, and increasing the stringency of the final probing procedure. The new technique has been NATA accredited.
Public Health Richard Bentham from Flinders University spoke about monitoring Legionella by systematic twice weekly testing at 28 cooling towers over 4 months in the summer season. All of the systems were maintained according to the current Australian standard. When data was analysed using time series correlograms very low correlation was found between sequential samples from a given unit. The majority of units (17/27) showed no correlation between samples taken less than 1 week apart. Since it takes about 10 days for the results of a Legionella test to be known, the Legionella numbers in the tower may have changed markedly in the interval. Thus attempts to monitor Legionella safety using infrequent testing are highly unreliable. Richard suggested that short term intensive Legionella monitoring for each system should be carried out to determine whether maintenance procedures are adequate, then frequent testing for total bacterial count should be used to check that the system was in a stable state.
Martyn Kirk from the Department of Human Services, Victoria / CRCWQT described a case-control study of Aeromonas gastroenteritis in Adelaide. This bacterium is commonly present in water supplies, especially in areas of low flow and low chlorine residual, but it is not known whether this is a significant source of clinical infections. The residential addresses of cases with Aeromonas gastroenteritis were classified according to their location on dead ends or loops in the water supply system. The addresses of randomly selected controls from the electronic White Pages were classified in the same way. It was found that cases were more likely to live on a main that terminated in a loop, and in one water supply area living on the last 50 metres of a dead end was also associated with increased risk. It should be noted that this study did not assess the water consumption of cases or controls, however the results suggest that Aeromonas infection may be associated with poor water quality.
Steve Conaghty of the NSW Health Department reported on the investigation of the oyster-associated Hepatitis A outbreak early this year. The usual incidence of Hepatitis A in NSW is around 15-20 cases per week, however in February the rate rose to 150 per week.
Within 4 days of the increase being observed (by which time 66 cases were known), a case-control study was instituted using controls from the White Pages matched on postcode. Over 64% of cases reported eating oysters, and in many cases the source was identified as Wallis Lake. On the strength of this result, a Press Release was issued and harvesting at the Lake was stopped. PCR tests on oysters harvested in early February showed the presence of Hepatitis A and several other enteric viruses.
As the average incubation period of Hepatitis A is about 28 days, it is inferred that the contamination occurred in December /January. This may have been associated with sewage contamination of the lake due to heavy November rainfall. Harvesting at the Lake resumed in May after PCR tests showed no virus. During the outbreak there were 467 cases and 1 fatality in NSW, and at least 250 cases in other states.
During discussion at the end of the talk, Steve noted that there was great reluctance on the part of locals to accept the evidence of the case-control study and it was only the PCR evidence which was considered convincing by them. Hepatitis A has no known hosts other than man, so human faecal pollution must have been the cause of the outbreak. There were various theories about the specific source of the pollution including overflows from a local sewage treatment plant, septic tank seepage and pleasure boats on the lake. However the investigation was not able to determine the source.
Dr Flavia Cicuttini
Flavia Cicuttini holds an MBBS degree from Monash University and a PhD from the Walter and Eliza Hall Institute. After completing her PhD in 1995, Flavia was awarded a NHMRC Neil Hamilton Fairley Fellowship to study at the London School of Hygiene and Tropical Medicine. During this year Flavia was also attached to St Thomas' Hospital, London.
On returning to Australia in 1996 she took up her present position as senior lecturer in the Department of Epidemiology and Preventive Medicine at Monash University. Flavia is also a Clinical Rheumatologist at the Alfred Hospital, and her particular area of research is in the area of quantitation of cartilage volume in studies of progression of osteoarthritis. In the CRCWQT, Flavia is leading a project on the health effects of fluoridation of drinking water supplies.
Dr Daniel Deere
Daniel Deere graduated from the University of Leeds with a Biotechnology degree and then from The University of Liverpool/Institute of Freshwater Ecology with a PhD in Environmental Microbiology. He is currently employed by CMPS&F Environmental in Melbourne in the Risk Assessment group headed by Stuart McConnell.
Following his PhD Daniel worked as a water quality microbiologist at a pharmaceutical company and held a number of post doctoral fellowships funded in turn by the Wain Foundation, The Royal Society and finally Macquarie University. His key research interests were development and validation of monitoring methods for waterborne pathogens. The work was in collaboration with the groups of Duncan Veal at Macquarie, Nick Ashbolt at UNSW and Raj Shanker at AWT.
Dr Brent Robertson
Brent Robertson holds a MBBS degree from Monash University and completed his general practice training early in 1997. He commenced his PhD in April 1997 in the Department of Epidemiology and Preventive Medicine at Monash University. His project comprises a number of related studies investigating whether drinking water is associated with the risk of cryptosporidiosis in the general population.
Whilst completing his PhD Brent hopes to develop skills in the area of environmental epidemiology, general public health and project management. His areas of research interest are diverse and include international health, the needs of developing countries, aid organisations, climate change and its effects, and the global population debate.
In the first stage of the review process, representatives from water industry bodies including WSAA and the CRCWQT will meet with the NHMRC early in 1998 to form a priority setting group which will provide advice to the National Health Advisory Committee.
Arsenic Number 1 Hazard in US
Arsenic has been designated as the Number 1 hazardous substance in the US by the Agency for Toxic Substances and Disease Registry (ATSDR). ATSDR and the US Environment Protection Agency carry out a regular 2 yearly review of hazardous compounds and rank them in order of priority. The 275 compounds considered in the review are those most commonly found at hazardous waste sites which are considered most in need of clean up. The priority ranking is determined using an algorithm based on 3 factors - the frequency of occurrence, toxicity and potential for human exposure. Arsenic replaced Lead in the number 1 spot in the 1997 ranking, the only new additions to the top 20 were polycyclic aromatic hydrocarbons which ranked at number 10.
Water Company “Not Guilty” on Crypto
A British judge has ruled that there was insufficient evidence to convict the South West Water company of supplying water not fit for human consumption, in connection with a 1995 outbreak of cryptosporidiosis which affected about 600 people. The epidemiological report produced by the local health authority outbreak control team was ruled inadmissible as evidence by the judge in the Bristol Crown Court, and as a result neither the identity of the alleged cases, nor the laboratory results demonstrating the cause of the illness could be legally proven.
The ruling was a setback for the Drinking Water Inspectorate which had brought the case against the company. A Press Release from the Department of the Environment, Transport & the Regions on 18th September quoted Mr Michael Meacher, Minister for the Environment, as saying “the result is most disappointing” and that he “will consider if additional powers are necessary in support of the necessary strong regulation of drinking water quality in the protection of public health”.
Lunar water mission
NASA’s first moon mission in 25 years will begin on 5 January 1998 with the launch of the Lunar Prospector probe from Cape Canaveral, Florida. An earlier fly-by mission by the probe Clementine detected unusual radar reflections near the Moon’s South Pole, leading to speculation that a body of ice may lie in the base of a huge crater there.
The Lunar Prospector will orbit the Moon at an altitude of about 63 miles, using a sophisticated array of instruments to seek evidence of minerals and ice. NASA scientists will look for ice by analysing the speed of neutrons emitted when cosmic rays hit the Moon’s surface - neutrons arising from the hydrogen in water molecules travel more slowly than those from heavier elements in rocks. The probe will also map the Moon’s surface and characterise the magnetic and gravitational fields during its 1 year mission. If the presence of ice is confirmed it will increase the feasibility of further lunar exploration as it could be used as a source of hydrogen for rocket fuel, oxygen to breathe and (of course) water to drink.
Crypto Handbook on the Web
The handbook “Cryptosporidium and Water: A Public Health Handbook” reviewed on p5 of our last issue is now available free of charge on the World Wide Web at:
http://www.cdc.gov/ncidod/diseases/crypto/crypto.htm
British anti-lead campaign launched
A consortium of organisations and individuals has launched a campaign to reduce domestic lead levels in Britain. Dr Erik Millstone, of the Sussex University Science Policy Research Unit was quoted in the 10th November edition of the Electronic Telegraph as saying that up to 1 in 10 British children under six years of age may be exposed to the toxic metal at levels sufficient to affect their development. It has been estimated that about half of all British homes contain old lead-containing paint, and about one third receive water through old lead pipes (either in the distribution system or household plumbing). The consortium is calling for urgent action to replace lead water pipes and a campaign to educate the public and professional painters about the correct methods for dealing safely with lead paint.
UK competition turns “fowl”
A water supply deal by Anglian Water, hailed as an example of the new competitive UK water industry, turned into an embarrassing failure when the company was unable to deliver an adequate water supply to a chicken processing plant. In an article liberally laced with “fowl” allusions the Electronic Telegraph of 4th December reported that after “poaching” the customer from a rival water supplier, Anglian Water had “egg on its face” when only a trickle of water emerged from the specially built 2 mile pipeline to the plant. Anglian had offered a 20-30% reduction in cost compared to the former supplier Essex and Suffolk Water, but processing plant operators had to hurriedly reconnect the old supply when the new pipeline failed to deliver.
Companies calls for veto rights on new homes
The Water Services Association of England and Wales recently called on the British Government to give water suppliers the right to veto new housing developments, or demand the incorporation of water saving measures such as recycling grey water for flushing toilets and watering gardens.
The Chief Executive of the WSA pointed out that while urban planners are obliged by law to consider the impact of development on the landscape, wildlife and transport links, there was no requirement to take into account the availability of water supplies. Forward estimates by the Department of Environment and Transport show that 4.4 million new homes will be built in England and Wales by 2016, with more than half located in the east and southeast regions of England - which are also the areas most vulnerable to drought.
At present water companies have no legal right to object to regional planning decisions, and may not even be notified about major development plans. An example cited by WSA was the building of a new cruise terminal at Dover which services 150 ships annually, each requiring up to 600,000 litres of water. The local water supply authority was not consulted about the development proposal.
Ahoy - viruses overboard!
The Centres for Disease Control recently reported that investigation of an outbreak of viral gastroenteritis associated with oysters had implicated human sewage from oyster harvesting boats as the source. Clusters of gastroenteritis associated with eating raw oysters were reported in 5 states with at least 493 people being affected. DNA sequencing of viruses isolated from the stools of infected people showed they were members of the calicivirus group, and similar viruses were isolated from the oysters although DNA sequencing of these was not possible.
The origin of the suspect batches of oysters was traced back through 26 retailers, 11 wholesalers and finally to 20 harvesters on the Louisiana coast. Seven out of eight oyster boats inspected during the investigation had inadequate sewage collection and disposal systems.
This is the third documented outbreak of viral gastroenteritis from oysters in the US since 1993. In one outbreak which affected at least 200 people, the source was believed to be a single oyster fisherman suffering from Norwalk virus gastroenteritis who admitted dumping raw sewage into the water while harvesting from the shallow oyster beds. In the second outbreak, a faulty sewage disposal system on an oil rig was implicated as the source. Paradoxically, the latest outbreak may have been partly caused by efforts to disperse a toxic algal bloom from the oyster producing region. A freshwater diversion was used to lower salinity in the cyanobacterial infested area, and the drop in salinity may have prolonged survival of the virus in the water.
(See also the Conference Report for details of the NSW oyster-associated Hepatitis A outbreak).
Contact Information
| Editor - Martha Sinclair | email martha.sinclair@med.monash.edu.au |
| Assistant Editor - Pam Lightbody | email pam.lightbody@med.monash.edu.au |
The printed version of Health Stream is available free of charge - to be added to our mailing list please contact Pam Lightbody (email above or fax + 61 3 9903 0576).