Vile Giardia bug in Sydney water
June 28 2007
It is the first such incident since the 1998 health scare which forced Sydneysiders to boil water for weeks.
The Daily Telegraph Online has confirmed that health officials found low levels of the bugs have been found.
The canal runs from the southern dams in the Illawarra into Sydney’s Prospect Reservoir. The bugs are believed to have been washed into the upper canal from the heavy rainfalls over recent weeks.
It is expected that Sydney Water will immediately cut the supply from these canals to ensure the bugs do not enter Sydney’s main drinking water supply.
Today Deputy Chief Health Officer Kerry Chant said no bugs had been detected in filtered water coming from the water filtration plants and there was no threat to public health.
The upper canal supplies about 20 per cent of water to Prospect Filtration Plant – which feeds treated water to Sydney homes. Warragamba Dam supplies around 80 per cent.
Water Minister Phil Koperberg said the filtration system was adequately dealing with the very low levels of the bugs.
He said his advice to residents was that the water was perfectly safe and met all health guidelines.
Yesterday, the State Government alerted Sydneysiders that Warragamba dam had been contaminated with two massive plumes of dirty water in what authorities say are similar circumstances to events that led to the 1998 Giardia contamination.
However, they insisted that no bugs had been found in this water – the main supply. Water will still be drawn from here.
In July 1998, routine water testing identified Cryptosporidium cysts and Giardia cysts at high levels, leading authorities to issue a warning for residents to boil water.
The Health Department at the time claimed that it had not led to any higher reporting of illness in relation to the contamination despite anecdotal evidence that hundreds of people had fallen ill as a result.
Sources have insisted, however, that the bugs this time have been found in “very low levels”
Government sources revealed yesterday that a dirty plume of water discovered in Warragamba Dam plume had moved 15 metres overnight, “which shocked them” and had now reached the dam wall, leading to a public alert being issued. They were still monitoring for the presence of the bugs in this water.
Prospect Reservoir holds around 3 week supply of water should water supplies be cut off from Warragamba Dam.
The first plume entered the dam on June 20, the second five days later.
The NSW Health Department advised yesterday that the plumes contained no pathogens – such as giardia or cryptosporidium which can cause sever gastro-intestinal illness – and did not pose any health risk or supply risk to Sydney’s drinking water.
However, testing overnight had revealed some traces of the bugs in the upper canal supplies from the Illawarra Dams which also feed Sydney’s water supply.
“It’s not the sort of stuff you would want coming out your tap,” said Water Minister Phil Koperberg said yesterday.
“(But) its important to stress as strongly as possible that there is no threat whatsoever to Sydney’s water supplies.”
The Sydney Catchment Authority has already been forced to change where it takes water from at Warragamba to avoid the dirty water entering the system and being delivered to Prospect Reservoir where Sydney’s drinking water supply is filtered and delivered to homes via the water mains.
The privately run filtration plant has been put on alert to upgrade it treatment in case any dirty water reaches the plant.
Ironically, the contamination has been caused by the 200mm of rain that has fallen over the catchment in the past two weeks.
It contains nutrients and debris washed into the dam by the floodwaters.
The 1998 water crisis led to significant changes to early warning systems and better filtration, to prevent a repeat.
Opposition leader Barry O’Farrell said the incident highlighted a lack of planning by authorities.
However, the NSW Health Department’s chief medical officer Kerry Chant said the monitoring system had never been better.
Ms Chant said authorities now had the capacity to source water from a number of different supplies which allowed it to isolate any contaminated water from ever entering the main system.
“In recent years, Cryptosporidium has come to be regarded as one of the most important waterborne human pathogens in developed countries. Over 30 outbreaks associated with drinking water have beenreported in North America and Britain, with the largest infecting an estimated 403,000 people (Mackenzieet al. 1994). Recent research has led to improved methods for testing water for the presence of humaninfectious species, although such tests remain technically demanding and relatively expensive.
Cryptosporidium is an obligate parasite with a complex life cycle that involves intracellular development in the gut wall, with sexual and asexual reproduction. Thick-walled oocysts, shed in faeces are responsible for transmission. Concentrations of oocysts as high as 14,000 per litre in raw sewage and 5,800 per litre in surface water have been reported (Madore et al. 1987). Oocysts are robust and can survive for weeks to months in fresh water under cold conditions (King and Monis 2007).
There are a number of species of Cryptosporidium, with C. hominis and C. parvum identified as the main causes of disease (cryptosporidiosis) in humans. C. hominis appears to be confined to human hosts, while the C. parvum strains that infect humans also occur in cattle and sheep. C. parvum infection sare particularly common in young animals, and it has been reported that infected calves can excrete up to 10 billion oocysts in one day. Waterborne outbreaks of cryptosporidiosis have been attributed to inadequate or faulty treatment and contamination by human or livestock (particularly cattle) waste.
C. hominis and C. parvum can be distinguished from one another and from other Cryptosporidium species by a number of genotyping methods. Infectivity tests using cell culture techniques have also been developed. Consumption of contaminated drinking water is only one of several mechanisms by which transmission (faecal-oral) can occur. Recreational waters, including swimming pools, are an important source of cryptosporidiosis and direct contact with a human carrier is also a common route of transmission.Transmission of Cryptosporidium can also occur by contact with infected farm animals, and occasionally through contaminated food.” ADWG 2011
“Although known as a human parasite for 200 years, Giardia has been regarded seriously as an agent of disease only since the 1960s. It has been identified as an important waterborne pathogen, and linked to many outbreaks of illness associated with drinking water, particularly in North America. Although the importance of this organism has been established, there are large gaps in knowledge about it, and there are no tests for identifying the presence of human infectious species in water.
Giardia has a relatively simple life cycle involving two stages: a flagellate that multiplies in the
intestine, and an infective thick-walled cyst that is shed intermittently but in large numbers in faeces. Concentrations of cysts as high as 88,000 per litre in raw sewage and 240 per litre in surface water havebeen reported (Wallis et al. 1996). Giardia is typically present in larger numbers in Australian sewagethan Cryptsoporidium. Cysts are robust and can survive for weeks to months in fresh water.
There are a number of species of Giardia, but human infections (giardiasis) are usually assigned to one, G. intestinalis (= G. lamblia and G. duodenalis). G. intestinalis infections have been reported from domestic and wild animals, but the host range of human infectious species is uncertain. Although substantial advances have been made in the sampling and counting of cysts, there are currently no established methods to identify human infectious organisms in water. Waterborne outbreaks of giardiasis have generally been linked to consumption of untreated or unfiltered surface water and contamination with human waste.
Consumption of contaminated drinking water is only one of several mechanisms by which transmission (faecal-oral) can occur. Recreational waters, including swimming pools, are also emerging as an important source of giardiasis. However, excluding outbreaks, by far the most likely route of transmission is by direct contact with a human carrier. Transmission of Giardia can also occur by contact with infected animals and occasionally through contaminated food.” ADWG 2011