February 19, 2013
Report on 2012 Darfield gastroenteritis outbreak released
The Community and Public Health division of the Canterbury District Health Board today released its report on last year’s outbreak of waterborne gastroenteritis in Darfield.
The outbreak occurred in July and August last year (2012) and resulted in 29 people testing positive for Campylobacter, a bacterial cause of gastroenteritis. In addition a further 109 people were defined as having probable Campylobacteriosis.
Dr Ramon Pink, Canterbury Medical Officer of Health, says the outbreak was the result of animal effluent entering a well, which was not adequately treated.
“The best approach to prevent contamination is to have several barriers in place between potential infection and water related illness,” Dr Pink says.
“In this case there were no additional barriers in place. When heavy rain caused animal effluent to enter the well the contamination was left untreated as it travelled to the tap.”
Dr Pink says Community and Public Health have made several recommendations and will continue to work with Selwyn District Council (SDC) to ensure further waterborne outbreaks do not occur.
Key recommendations in the report include:
• An alternative ground water source capable of meeting the water supply requirements of the Darfield population should be found.
• A multi-barrier approach to drinking water supplies involving protection, monitoring and maintenance of the source. Treatment and distribution should be adopted, which is consistent with New Zealand Drinking Water legislation.
• If the Waimakariri River is to be used as a future water source (including for supplementation purposes) chlorination needs to continue and it needs to be included in a comprehensive risk management plan covering all weather events.
Murray England, Selwyn District Council Asset Manager for Water Services, says the Council have accepted the Community and Public Health recommendations and has begun implementing these as a priority.
“A month before the outbreak Council was forced to revert back to the river supply because of problems with our deep bore system. These problems have now been fixed and this has allowed us to return to our deep bore. Repeated testing has found water from this source to be free of microorganisms, meaning it is safe to drink,” Mr England says.
“We were very concerned by the contamination that occurred in Darfield and will be continuing to upgrade our water supplies to ensure residents have access to safe drinking water.”
Actions taken or planned by Selwyn District Council to improve water safety include:
• The construction of a second deep bore water source for Darfield. This can be used as a back-up supply instead of the Waimakariri supply if there are any problems with the current supply. Consent for the bore has been approved and construction is planned to start in April.
• Isolating the current alternative water supply for Darfield from the Waimakariki river from the main water supply so that it is not cross contaminated. If it needs to be used as a drinking water source chlorination will begin so that it is safe to drink.
• Constructing a new reservoir to store water at Darfield, this will reduce aeration of the system and help decrease water temperature variations in residents’ hot water systems.
• Improved internal water monitoring processes to identify any contamination of the supply and improved public notification processes when boil water notices are issued so that people are informed of this as soon as possible.
• Working with the Canterbury District Health Board to finalise public health risk management plans for all water supplies.
To read the report click on the link: http://www.cph.co.nz/Files/DarfieldOutbreakCommunityReport.pdf or http://www.cph.co.nz/About-Us/Drinking-Water/Default.asp