MICROBIOLOGICAL QUALITY OF SHELLFISH IN ESTUARINE AREAS
JOINT AGENCY RESEARCH REPORT 2009
Forward
This project was funded by New Zealand Food Safety Authority, Environment Bay of Plenty, Toi Te Ora – Public Health, Tauranga City Council, and Western Bay of Plenty District Council
This report was prepared by Paul Scholes, Environment Bay of Plenty; Dr Gail Greening, Institute of Environmental Science and Research; Dr Donald Campbell & Jim Sim, New Zealand Food Safety Authority; John Gibbons-Davies, Graham Dohnt, Tauranga City Council; Kelvin Hill & Ilze Kruis, Western Bay of Plenty District Council and Dr Phil Shoemack & Annaka Davis, Toi Te Ora – Public Health.
Cover photo: Anzac Bay, Tauranga Harbour: Supplied by Western Bay of Plenty District Council.
DISCLAIMER
None of the project organisations nor any of its employees makes any warranty, express or implied, or assumes any legal liability or responsibility for use of this Report or its contents by any other person or organisation.
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 2 Acknowledgements
The project group gratefully acknowledges the contributions of Graham McBride – National Institute of Water & Atmospheric Research, Mark Arundel of Bethlehem Pharmacy, members of Tauranga Moana Customary Fisheries Committee in the planning and development of the project. Thanks to Tony Wood, Aquatek who collected the shellfish and water samples; and also to the Environmental Science & Research Ltd Environmental and Food Virology team for the viral analysis.
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 3 Executive Summary
Towards the end of 2006 recreational shellfish monitoring showed an increase in elevated bacterial levels in shellfish beds within Tauranga harbour adjacent to the city of Tauranga. Recreational water quality monitoring also identified contamination events which could result in pathogenic bacteria and viruses being present at harmful levels in shellfish.
Environment Bay of Plenty (EnvBOP), Tauranga City Council, Western Bay of Plenty District Council and Toi Te Ora – Public Health (TTO) agreed it was necessary to obtain better information on the pathogen levels in shellfish stocks so the public could be better informed on the risks of eating shellfish from local beds.
Two estuarine areas were sampled in this study, Tauranga Harbour and Waihi Estuary. Monthly shellfish and water sampling was carried out over a 12 month period to obtain information on the usual microbiological and viral quality of shellfish. Comprehensive sampling was also carried out after two significant pollution events.
This study found that enteric virus contamination of shellfish is occurring in the Tauranga Harbour and Waihi Estuary. Shellfish from a few sites - namely Tilby Point and Pilot Bay were found to be regularly contaminated with viruses. These two sites are closest to the urban area and main cities of Tauranga and Mount Maunganui. Over the study period, norovirus levels were generally low in shellfish except following the significant sewage spill.
Following a sewage pollution event, high levels of norovirus were detected in shellfish located 50 m from the source. Norovirus remained detectable in shellfish 50m from the source for up to 3 months following the sewage pollution event.
Low levels of norovirus were detected in shellfish from three of the six sites in the Tauranga harbour following a rainfall event. There was good correlation between the presence of norovirus and human-associated F-RNA bacteriophage in shellfish after a sewage pollution event but not after a rainfall event. This suggests that the lower level norovirus contamination was not associated with a significant quantity of human sewage being discharged. The higher levels of faecal coliforms found after this event is more likely to be animal in origin from land run-off.
It can be concluded that there is no distinct relationship between the faecal indicator bacteria and positive viral results. This demonstrates that indicator bacteria may not be reliable indicators of viral contamination in shellfish collected in this survey and vice versa. This demonstrates that shellfish may not be safe to eat even when the bacterial quality is within currently accepted microbiological limits.
There was repeat viral contamination found in parts of the harbour adjacent to urban areas. This supports New Zealand Food Safety Authority’s general advice not to collect shellfish near urban areas because of the ongoing impact of stormwater and sewage-related contamination.
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 4 Contents
Forward 2
Executive Summary 4
Introduction 9
Project Goal & Objectives 10
Methodology & Sampling Sites 11 Study Area 11 Sampling Sites 11 Shellfish Species 13 Sampling Regime 14 Sample Collection & Analysis 14 Microbiological Limits 16
Supporting Information 18 Environment 18 Viral & Bacterial Indicators 18 Human Health 19
Monthly Surveillance Results 24 Indicator Bacteria Results for Shellfish 24 Viral Results for Shellfish 25 Indicator Bacteria Results for Shellfish Adjacent Water 27
Adverse Pollution Event Results 29 Sewage Overflow Event 29 Rainfall Event 33 Discussion on Sewage Overflow & Rainfall Events 39
Comparison of Results with Microbiological Limits 44 Shellfish Adjacent Water Quality 44 Shellfish Quality 44 Other Microbiological Criteria 46
Bacteria & Viral Indicators of Contamination 48
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 5 Discussion 50 Sources & Pathways of Faecal Contamination 50 Longevity & Extent of Microbiological Contamination 53 Public Health Risk Assessment 54
Conclusions 56
Recommendations 57
References 58
Appendices 61 Appendix 1 Sampling Site Location Details 62 Appendix 2 Water Quality Surveillance Results 63 Appendix 3 Shellfish Quality Surveillance Results 68 Appendix 4 Sewage Overflow Adverse Pollution Event Sampling 72 Results Appendix 5 Rainfall Adverse Pollution Event Sampling Results 74 Appendix 6 Rainfall Adverse Pollution Event Data 77 Appendix 7 Total Daily Rainfall Data 81 Appendix 8 Average Daily River Flow Data 84 Appendix 9 Sewage Reticulated and Non-Reticulated Areas 86 Appendix 10 Reticulated Sewage Overflow Data 89
List of Tables Table 1 Shellfish Site Locations and Species 12 Table 2 Water Sample Site Locations 12 Table 3 Scale of Norovirus Load in Shellfish 15 Table 4 The number of trips taken by non-commercial harvesters to 20 collect shellfish, and the species of shellfish targeted by the harvesters Table 5 Estimate of annual non-commercial harvest of shellfish in 20 New Zealand, 1999-2000, and the most common harvesting methods Table 6 Outbreaks of disease notified to the Medical Officer of 22 Health, in the Bay of Plenty district from October 2007 to October 2008 Table 7 Number of cases of gastroenteritis between 1997 and 2004 23 where shellfish was suspected as being the causative agent. Table 8 Statistics for Indicator bacteria results in shellfish over the 25 12 month survey Table 9 Virus results in all shellfish sampled monthly over 12 26 months.
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 6 Table 10 Percent Positive Virus and FRNA Bacteriophage Results 38 over Rain Event Sampling Table 11 Presence of norovirus in shellfish samples following 40 adverse pollution events Table 12 Virus results for shellfish sampled monthly over 12 months 42 (including events) Table 13 Faecal coliform statistics for shellfish waters, October 2007 44 to September 2008 Table 14 Comparison of indicator bacteria and virus results in 48 shellfish and shellfish collecting waters based on monthly sampling over 12 months Table 15 Catchment characteristics for potential sources of faecal 52 contamination
List of Figures Figure 1 Shellfish and Water Sampling Site Locations 13 Figure 2 Number of Shellfish Samples Positive for Norovirus and 26 Adenovirus Figure 3 Indicator bacteria concentrations Tauranga Harbour, 27 October 2007 to September 2008 Figure 4 Indicator bacteria concentrations Waihi Estuary, October 28 2007 to September 2008 Figure 5 Indicator bacteria concentrations in shellfish for 4 sites, 30 Tauranga Harbour Figure 6a Norovirus occurrence and levels in shellfish samples 31 following sewage overflow event Figure 6b Norovirus GI and GII levels in shellfish following sewage 32 overflow event Figure 6c Norovirus GI and GII levels in shellfish following sewage 32 overflow event Figure 7 Occurrence of norovirus (NoV) and F-RNA phage 33 genogroups in shellfish following point source sewage pollution event Figure 8 Indicator bacteria concentrations in shellfish and total daily 34 rainfall over a rainfall event, North Tauranga Harbour and Waihi Estuary Figure 9 Indicator bacteria concentrations in shellfish and total daily 35 rainfall over a rainfall event, South Tauranga Harbour Figure 10 Indicator bacteria concentrations in shellfish, Waihi Estuary 36 and total daily flow Pongakawa River Figure 11 Faecal coliform concentrations in shellfish at 5 sites, South 37 Tauranga Harbour and Wairoa River daily total flow Figure 12 Occurrence of norovirus (NoV) and F-RNA phage 39 genogroups in shellfish samples following adverse rain event Figure 13 Indicator bacteria concentrations in shellfish after a major 40 rain event and sewage contamination event, Opposite Pilot Bay
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 7 Figure 14 Comparison between F-RNA phage and norovirus (NoV) 41 occurrence in point source and rainfall adverse event samples Figure 15 Norovirus positive samples from each site by month, 42 including event samples Figure 16 Percentage of positive Norovirus GII results over 12 months 43 monitoring Figure 17 E. coli concentrations in bivalves, sampled monthly October 45 2007 to September 2008 Figure 18 Faecal coliform concentrations in bivalves, sampled monthly 47 October 2007 to September 2008 Figure 19 Faecal coliform concentrations in shellfish at selected sites 49 and positive GII norovirus
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 8 Introduction
Towards the end of 2006 recreational shellfish monitoring showed an increase in elevated bacterial levels in shellfish beds within Tauranga harbour adjacent to the city of Tauranga. Recreational water quality monitoring also identified contamination events were occurring. It was believed that these events could be causing pathogenic bacteria, viruses and protozoa to be present at levels in shellfish that are harmful to humans if consumed.
Environment Bay of Plenty (EnvBOP), Tauranga City Council, Western Bay of Plenty District Council and Toi Te Ora – Public Health (TTO) agreed it was necessary to obtain better information on the pathogen levels in shellfish stocks so the public could be better informed of the risks of collecting and eating shellfish from local beds. As both Tauranga Harbour and Waihi Estuary are used extensively for gathering and consumption of non-commercial shellfish, and both estuaries have previously had high faecal indicator bacterial levels, they were selected for monitoring.
Over the last few years the New Zealand Food Safety Authority has funded the development of norovirus testing for shellfish and was interested in proving the methodology in a field situation and also gathering data to support predictive modelling of viral contamination. This would facilitate identification of contamination in similar areas without the necessity to undertake expensive testing of shellfish samples. To this end these organisations agreed to fund a joint project to fill some of the current information gaps relating to microbiological contamination of shellfish and adjacent waters.
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 9 Project Goal & Objectives
Project Goal
“To limit shellfish borne illness from shellfish gathered in Tauranga Harbour and Estuary.”
This goal was consistent with Environment Bay of Plenty Ten Year Plan 2006-2016 in that the water quality of Bay of Plenty harbours, estuaries and beaches are suitable for contact recreation and shellfish gathering. Tauranga City Council has a similar long term goal to this project which was to establish baseline data for water and shellfish quality in Tauranga Harbour, which will then allow Council to measure any changes found during incident monitoring. It will also be the starting point for on- going monitoring of the health of the water and shellfish quality within our harbour." The project goal was also identified as a community outcome of Western Bay of Plenty District Council long term plan to ensure that the District’s natural environment is protected, maintained and enhanced and that all areas in the District served by the Council’s reticulated wastewater disposal systems meet acceptable health, safety and environmental standards.
District and city councils as well as Toi Te Ora have legislative responsibilities to improve, promote and protect public health 1 and a function of the Food Safety Authority is to protect and promote public health and safety, all of which align with the project goal.
Project Objectives
assess bacterial and viral quality of shellfish in Tauranga Harbour and Waihi Estuary determine if viral contamination of shellfish is occurring and if so to what extent determine for how long shellfish remain contaminated after an adverse pollution event determine what adverse pollution conditions and/or environmental parameters give rise to bacterial and/or viral shellfish contamination determine pathways of human faecal contamination in shellfish (if present) assess if bacterial or viral indicators of contamination in shellfish are good indicators of viral contamination assess the shellfish quality against recommended guideline values for human consumption determine feasibility of using a desk-based assessment on a review of catchment pollution sources rather than undertake costly ongoing shellfish/water sampling programmes
1 Health Act 1956
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 10 Methodology & Sampling Sites
Study Area
Two estuarine areas were sampled in this study, Tauranga Harbour and Waihi Estuary.
Tauranga Harbour is a large tidal estuarine inlet with two entrances with a total area of 201 km 2. The estuarine lagoon is impounded by a barrier island (Matakana Island) and two barrier tombolos. Mount Maunganui at the southern entrance and Bowentown to the north (Park, 1991). The estuary is predominantly shallow with approximately 66% of its total area being intertidal.
There are three predominant harbour basins. The largest basin is in the north and this is separated from the southern basins by intertidal flats in the central area of the harbour. The other basin is smaller and includes several sub-estuaries and large bays. At mean high water the northern basin has a volume of approximately 3 3 177,702,000 m and the southern basin a volume of 277,518,000 m .
2 The northern harbour catchment is the smallest with a total area of 270 km and a 3 2 mean freshwater inflow of 4.1 m /s. The Wairoa River catchment at 460 km and mean freshwater inflow of 12.1 m 3/s is the largest feeding into Tauranga Harbour. In the northern harbour the freshwater inflow represents only 0.1% of the harbour volume per tidal cycle while the southern input represents 0.48%.
2 The harbour catchment covers an area of approximately 1,300 km and is used extensively for horticulture and agriculture. At the southern end of the harbour, the city of Tauranga and surrounding area supports a large residential population (over 100,000). Near the southern entrance the harbour has well developed port facilities.
The 2.4 km 2 shallow tidal inlet that forms Waihi Estuary is impounded by a long spit upon which the Pukehina community has settled. Much of the estuary dries at low tide with the main channel providing the conduit of water to a few narrower channels.
The estuary is fed freshwater from a number of stream fed drainage canals. These waters pass through a catchment of exotic and native forests in the headwaters to mixed horticulture, sheep, beef farms and dairy farms on the rolling hill country and plains. Drains tend to provide a high level of nutrients and bacteria to the estuary and there is also septic tank contamination from the local communities.
Sampling Sites
The sampling sites were based on the collective knowledge of the project team. The historical and current monitoring data collated between the project agencies was also considered when choosing the sites. This data identified areas of shellfish and environmental contamination from known or unknown sources; potential contamination sources; potential freshwater influences; shellfish stocks to sustain the sampling regime; the distribution of sites between reticulated and septic tank communities; tidal flows and the location of marae in the project area. Also taken into consideration was the extent of collection, frequency, most popular harvesting sites and which species were gathered from where. This information was based on
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 11 the project team member knowledge and discussions with Craven Dunn Customary Fisheries Officer of the Ministry of Fisheries, and the Tauranga Moana Iwi Customary Fisheries Committee.
Shellfish were sampled from five sites within Tauranga Harbour and one at Waihi. These are listed in Table 1 and shown in Figure 1 below.
Table 1 Shellfish Site Locations and Species Shellfish Sample Site Location Shellfish Species Local Authority A. Pios Beach Sandbar Cockles Western Bay B. Between Plummers Point Road and Oysters Western Bay Snodgrass Road, Te Puna C. End of Te Puna Road Horse Mussel Western Bay D. Fergusson Park, Otumoetai – Tilby Point Pipi Tauranga E. Pilot Bay Sand Bar Pipi Tauranga F. Waikareao Entrance Cockles Tauranga G. Waihi Estuary – Main Channel Pipi Western Bay
Monthly water samples were taken at 13 locations listed in Table 2 and shown in Figure 1 below.
Table 2 Water Sample Site Locations Water Sample Sites Site No. Local Authority Bowentown Boat Ramp BOP150022 Western Bay Tanners Point Jetty BOP150027 Western Bay Kauri Point Jetty BOP150023 Western Bay Ongare Point BOP720025 Western Bay Pahoia Beach Road BOP150026 Western Bay Omokoroa Wharf BOP150014 Western Bay Te Puna Beach, Pitua Road BOP150013 Western Bay Otumoetai, Beach Road BOP720004 Tauranga Waipu Boat Ramp BOP720024 Tauranga Toll Bridge Marina BOP150021 Tauranga Pilot Bay BOP150030 Tauranga Maungatapu Bridge BOP150011 Tauranga Waihi Domain – Waihi Estuary BOP150006 Western Bay
A control site was considered inappropriate for the purposes of this project and therefore not included. Potentially every site could be affected by contamination from runoff lending no site to be ‘pristine’ and therefore a suitable control.
* Seven months into the project the sampling site located at Waipa Road Te Puna was found not to contain a sufficient stock of Horse Mussel to complete the sampling plan. Consequently Cockles from Waikareao Estuary were sampled for the remaining 4 months. All other sites had sufficient stock.
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 12 Figure 1: Shellfish and Water Quality Sampling Site Locations
Shellfish Species
Only bivalve shellfish (which filter-feed) were included in the project because they accumulate and concentrate bacteria and viruses. Bivalve shellfish species were restricted to those collected by recreational gatherers from the specified project area. The species which met the criteria were identified as Cockles, Pipi, Horse Mussels, and Oysters. Although scallops are present in the harbour and are also bivalve filter feeders, this species was not included because most consumers remove the gut and cook scallops before consumption, greatly reducing the risk of illness. Additionally, because scallops are mobile any source of contamination may be more difficult to identify if they were found to be contaminated. The project team was not aware of any reported viral outbreaks related to scallop consumption.
Species collected were:
Cockle ( Austrovenus stuchburyi ): found throughout intertidal and subtidal muddier areas only abundant in harvestable numbers at a few locations.
Pipi ( Paphies australis ): often abundant around the mouth of the estuaries but extend to sandy areas of the inner estuary.
Oyster (Crassostrea gigas ): commonly found in location cemented to roots of mangroves by their lower valve in the intertidal zone.
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 13 Horse mussel (or fan) ( Atrina zelandica ), are found mainly on muddy-sand substrates in the lowest inter-tidal and sub-tidal shallows of mainly sheltered waters.
Sampling Regime
Monthly shellfish and water sampling was carried out over a 12 month period to obtain surveillance or background information on the usual microbiological and viral quality of shellfish. Comprehensive sampling was also carried out after two suspected adverse pollution events. A suspected adverse pollution event was defined as a:
sewage overflow from Council reticulated wastewater system >50 cubic metres in volume or; rain event which increases water flows in the rivers within the Tauranga Harbour or Waihi Estuary catchment to at least twice the median flow
Suspected adverse pollution events likely to be the most significant were targeted and a year long sampling regime was used to reflect real world risk for shellfish gatherers.
Sample Collection & Analysis
Shellfish Samples
Flesh of the shellfish was analysed for faecal coliforms, Escherichia coli ( E. coli), and enterococci. The shellfish digestive gland tissue was also analysed for norovirus, adenovirus and for additional event samples, FRNA bacteriophage. Adenoviruses were chosen because previous studies showed this virus to be common in shellfish and wastewater in New Zealand (Greening & Lewis, 2007). There has been international discussion to use adenoviruses as an ‘indicator’ of viral contamination rather than enteroviruses or phage and this project supports these discussions. Adenoviruses are stable, persist for long periods in the environment and are indicative of human contamination (Pina et al. 1998). Hepatitis A virus (HAV) was not analysed for as HAV is uncommon and of low morbidity in New Zealand. There is little evidence of Hepatitis A virus in shellfish in New Zealand and most cases in New Zealand have been due to person to person spread rather than consumption of contaminated food or water. In a recent study of virus prevalence in New Zealand shellfish (Greening & Lewis, 2007), the Institute of Environmental Science and Research (ESR) found the same percentage of shellfish samples positive for adenoviruses and noroviruses.
Water Samples
The samples were analysed for faecal coliform , E. coli and enterococci. Water samples were not analysed for viruses because the method of analysis available to test viruses in sea water had not been validated by ESR at the time of the study.
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 14 Water samples were taken in accordance with the Guidelines 2 and were used as a management tool to measure any change from conditions prevailing at the time of assessment. The recreation and shellfish water quality guideline limits were also used when assessing the impact of pollution from surface run-off after rainfall, and of tidal movement under storm conditions. Such factors were used to decide when gathering should be discouraged in shellfish-gathering areas when weather conditions may cause pollution in the future.
Sampling to test compliance of shellfish gathering water was carried out over the whole project time period. This was to ensure a sufficient number of samples were gathered to provide a reasonable statistical power in testing for compliance for both the median limit and the 90% samples limit.
Viral Analysis
Norovirus analysis of shellfish was carried out using the Institute of Environmental Science and Research IANZ accredited method (Greening & Hewitt, 2008). The method comprises a virus recovery step using protease digestion followed by extraction of viral nucleic acid. Two-step real-time polymerase chain reaction (RT- PCR assays were used to detect norovirus GI and GII strains respectively (Kageyama et al., 2003). An internal armoured RNA control, which detects the presence of inhibitors and indicates when there may be false negatives, was an integral part of the method. These norovirus assays detect human noroviruses but not animal noroviruses.
A scale was introduced (Table 3) to provide an estimate of norovirus load in each shellfish sample. The scale was derived from the average estimated levels in > 300 shellfish samples analysed at ESR in 2007-2008. RTPCRU is the abbreviation for ‘reverse transcription- polymerase chain reaction units’. This is the detection unit for the assay. It refers to the actual copy numbers of the target region of the Norovirus RNA genome detected in the test. However this target region is very short and it is not representative of the complete infectious norovirus genome. Therefore it is not possible to equate RTPCRU with numbers of infectious norovirus.
Table 3 Scale of Norovirus load in shellfish Negative no virus detected in any of 4 replicates Low Positive < 80 RTPCRU 3 per gram of shellfish gut tissue equivalents, and less than 4 replicates positive Moderate Positive 80-160 RTPCRU per gram of shellfish gut tissue equivalents and 4/4 replicates positive High Positive 160-1000 RTPCRU per gram of shellfish gut tissue equivalents and 4/4 replicates positive Very High Positive > 1000 RTPCRU per gram of shellfish gut tissue equivalents and 4/4 replicates positive
The scale criteria of ‘low, moderate, high and very high’ is based on the detection method for shellfish and is derived from ESR’s results for over 300 New Zealand shellfish samples. It is based on the RTPCRU or copy numbers of the target region detected for each sample. The limit of detection is 20 RTPCRU or copies/g and the limit of quantitation is 80 copies per gram of shellfish gut. Virus recovery from shellfish is inefficient and may only be 20-30% of the actual number of viruses
2 Ministry of Health and Ministry for the Environment Guidelines for Recreational Water Quality, June 2003 3 real-time reverse transcription polymerase chain reaction unit
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 15 present, so the presence of 20 copies may represent 100 actual virus copies per gram. Given that people generally eat more than 1 gram of shellfish flesh and so even a low copy number can be a risk. Internationally, presence of any norovirus in shellfish is regarded as a potential risk because of the unknown infectivity status and the presumed low infectious dose of the virus. It cannot be assumed that all noroviruses in shellfish are infectious, but it is not possible to determine the proportion that are infectious. Consequently, in common with international practice, the New Zealand Food Safety Authority recommends a zero tolerance for noroviruses in commercial shellfish.
Human adenovirus analysis was carried out by real-time PCR assay on the nucleic acid extracts obtained following the virus recovery process (Heim et al., 2003).
F-RNA bacteriophage were identified and genotyped using a novel semi-quantitative multiplex real-time RT-PCR assay which also determined whether the contamination source was predominantly animal or human (Wolf et al., 2008).
Bacterial Analysis
Bacteria analysis of shellfish and water was carried out using Environment Bay of Plenty IANZ accredited method. Shellfish were analysed for Escherichia coli (E. coli ), enterococci and faecal coliforms using the Most Probable Number method of analysis (MPN) as per Standard Methods for the Examination of Water and Wastewater (2005) for faecal coliforms and enterococci. For E. coli the MPN method is based on the Recommended Procedures for the Examination of Seawater and Shellfish (1985).
Water samples were analysed for E. coli , enterococci and faecal coliforms. All analyses were performed using membrane filtration as per Standard Methods for the Examination of Water and Wastewater (2005) for faecal coliform and E. coli and Method No. 1600, USEPA 1986 EPA-821-R-97-004 for enterococci.
Microbiological Limits
Shellfish Quality
No specific microbiological guideline criteria exist for shellfish gathered for personal consumption or non-commercial purpose. However, NZFSA advised that the commercial shellfish limits could be used in a non-commercial setting. Consequently, the microbiological limits outlined in the New Zealand Food Safety Authority Animal Products (Specifications for Bivalve Molluscan Shellfish) Notice 2006 for commercial shellfish quality were applied. Likewise, no published norovirus standards exist; however as only a few Norovirus particles may be enough to infect a healthy person a nil tolerance for norovirus is applied. This is consistent with management of commercial shellfish harvesting areas. Accordingly a surveillance shellfish flesh sample will be considered fit for human consumption when the following bacteria and virus limits are met.
Faecal coliform limits have been used historically for shellfish quality assessment but these have been abandoned in recent years in favour of E. coli .
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 16 the E. coli median MPN of the shellfish samples must not exceed 230 E. coli per 100g and not more than 10% of the samples must exceed an MPN of 700 per 100g 4 and; no detectable norovirus genome sequences per gram of gut tissue 5
Adjacent Shellfish Water Quality
The collection of samples for surveillance water quality shall meet the recreational shellfish-gathering bacteriological guideline value outlined in the Microbiological Water Quality Guidelines for Marine and Freshwater Recreational Areas, Ministry for the Environment and Ministry of Heath: “The median faecal coliform content of samples taken to meet the guideline standards should not exceed 14 per 100ml, and not more than 10% of samples should exceed 43 per 100ml.”
To clarify, 10% of the samples means, of 19 samples collected at one site, only 1 sample can exceed the bacterial standard and of 20 samples then 2 can exceed the standard. A sufficient number of samples were gathered throughout the project period to provide a reasonable statistical power in testing for compliance for both the median limit and the 90% samples limit.
4 NZFSA Animal Products (Specifications for Bivalve Molluscan Shellfish) Notice 2006 and The Food Standard Code Australia New Zealand (2006) 5 There are no published standards for norovirus, however in practice a nil tolerance of norovirus genome fragments is applied.
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 17 Supporting Data
Environment
The following environmental data was collected when sampling shellfish and water samples: water temperature, wind speed, wind direction, water roughness, percent cloud cover, tide, and any other observations worthy of note (e.g. numbers of water fowl that may influence faecal bacterial loadings).
The National Institute of Water and Atmospheric Research is currently conducting a Tauranga sedimentation modelling project which includes hydro-dynamic modelling of the harbour. This work may update information currently known about residence time of waters in various parts of the harbour. Previously, dye tests have been done by Environment Bay of Plenty which shows that flushing of waters from upper sub- estuaries is poor and water entering the harbour from rivers may oscillate for four of more tidal cycles before mixing with the main basin waters.
Waters in the main basins are generally flushed out the harbour entrance but depending on the various factors such as tidal cycle, winds, temperature, and salinity water may re-enter the harbour on the following incoming tide (McIntosh, 1994).
Waihi Estuary is a relatively shallow estuary and the water is thought to flush in a similar manner to other shallow estuaries such as Ohiwa which is well flushed within one or two tidal cycles (Park, 2005).
Daily hydrographical and meteorological data was collated throughout the project by EnvBOP to assist the identification of an adverse pollution event.
Viral and Bacterial Indicators
The viruses studied in this project were adenovirus and norovirus, both of which can cause disease in humans. These viruses are transmitted via the faecal – oral route, are excreted in faeces and are therefore found in sewage discharges from wastewater plants, sewerage pipes, septic tank leakages and boats. The waters the shellfish are growing in can become contaminated with viruses through such sources or directly by people.
When bivalve shellfish such as pipi, mussels, oysters and cockles feed in sewage- contaminated water, they take up the viruses at the same time as they take in water, algae, bacteria and food particles. The shellfish bioaccumulate any viruses and retain them for long periods, whereas bacteria are generally depurated within 2-3 days. The human viruses can stay in the shellfish gut tissues for weeks so that the shellfish may be unsafe to eat (Lees, 2000; Greening et al., 2003). Consumption of virus-contaminated shellfish can cause illnesses such as gastroenteritis and hepatitis A, which can then be transmitted from person to person and spread through the whole community.
Human norovirus is believed to be the most common cause of epidemic non-bacterial gastroenteritis worldwide (Koopmans 2008). These viruses commonly cause outbreaks of gastroenteritis in retirement homes, hospitals, institutions, schools and cruise-ships from person to person spread as well as via food. Noroviruses are divided into 5 main genogroups GI-GV, of which GI, GII and GIV infect humans and
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 18 GIII and GV strains infect animals. Some distinct strains of GII have been found in pigs. Norovirus outbreaks are common in New Zealand with the majority of outbreaks caused by GII strains. In New Zealand, GIII animal noroviruses have been detected in faeces from sheep and cattle and GII animal noroviruses in pig faeces (Wolf et al., 2009).
Adenoviruses are common pathogens of animals and humans. There are many different types, each of which generally infects only a single species. They cause a range of human diseases including gastroenteritis, acute respiratory disease, pneumonia and conjunctivitis. Some infections may be asymptomatic. Adenoviruses are stable in the environment, occur in greater numbers in sewage and sewage- polluted waters than other enteric viruses and survive longer than enteroviruses and hepatitis A virus (Enriquez et al., 1995; Mena & Gerba, 2008).
Bacterial indicators such as E coli and faecal coliforms have proved to be inadequate for assessment of enteric viral contamination because they are less resistant to inactivation by environmental factors such as sunlight, salinity, chlorine disinfection and other wastewater treatment processes and are removed from shellfish within 2-3 days. F-RNA bacteriophages (phage) are bacterial viruses that are commonly found in the environment and can be derived from both animal and human sources. Genotyping of F-RNA phage is helpful for distinguishing between animal and human sources of pollution because some phage types are mainly associated with animals and others are associated mainly with humans. FRNA phage are found mainly in wastewaters, sewage, septic tanks and effluents and less commonly in human and animal faeces, although some bird faeces have been found to contain high numbers of phage (Calci et al. 1998).
F-RNA phage are divided into 4 genogroups, GI,GII,GIII and GIV. Groups II and III are found mainly in human waste whereas GI and GIV are associated more with animal waste. These are not exclusive categories but can be used as a guide to the major source of pollution. GIII strains have been found occasionally in animal waste as well as in human waste and GIV strains are reported to be rare (Calci et al., 1998; Havelaar et al.1990).
Human Health
Harvesting & Consumption
A year long survey in 1996 based on telephone interviews and diaries collected some national statistics on non-commercial shellfish collection in New Zealand. The species of shellfish collected varied with habitat and accessibility throughout the country, but some species (e.g. scallops, mussels and pipis) are targeted more often than others.
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 19
Table 4: The number of trips taken by non-commercial harvesters to collect shellfish, and the species of shellfish targeted by the harvesters (1996 survey).
Gathering shellfish from the Tauranga harbour and Waihi Estuary is not limited to the local population as visitors come from Auckland, Hamilton, Rotorua and as far south as Turangi to gather. (pers .comms, Tauranga Moana Customary Fisheries Committee)
More recent surveys on the non-commercial harvest of shellfish have been done, including estimates from telephone interviews and diaries. The most common harvesting method used for collection is indicated in Table 5.
Table 5: Estimate of annual non-commercial harvest of shellfish in New Zealand, 1999-2000, and the most common harvesting methods.
Shellfish beds in Tauranga Harbour and Waihi Estuary are easily accessible and due to the calm conditions shellfish is often collected from these areas rather than the open coast. (per coms. Tauranga Moana Customary Fisheries Committee & Ministry of Fisheries).
The consuming population
There have been some attempts to characterise the non-commercial shellfish harvesting population by ethnicity. It has been estimated that of all those participating in non-commercial shellfish gathering over a year, 14% are Maori, 2% are Pacific people, and 84% belong to other ethnic groups (Wilson, 1996). A survey
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 20 conducted in the Whangateau Harbour (north of Auckland) found that of those collecting cockles, 54% were Maori (collecting 55% of the total cockles, by weight), 26% were New Zealand Europeans (19% of cockles), 15% were Asian (9% of cockles), and 4% were Pacific people (9% of cockles) (Kearney, 1999). A survey of Maori households in Northland showed that 42% of the households collected seafood more than once a week and 52% at least fortnightly. Only 9% did not collect seafood at least monthly (n=499) (Hay, 1996). While there is no clear pattern of ethnicity, there is some suggestion that Maori, Pacific and Asian peoples are over-represented in the shellfish harvesting population compared to the ethnic composition of New Zealand as a whole (Drey & Hartill, 1993). Certainly the proportion of ethnic groups varies with location, and ethnicity may also affect the target shellfish species and selection of collection site (Hay et al., 2000).
The non-commercial harvesting of inter-tidal shellfish is highest in the summer and lowest in the winter. Seasonal restrictions also influence harvesting patterns. The greatest harvesting occurs on public holidays and weekends and is likely related to the influx of people from urban areas to the coast. Harvesting can sometimes increase prior to public holidays and long weekends, particularly by Maori, and is attributed to the preparation for visits from whanau and Marae events (Hay et al.2000). 6
Locally there are 26 marae in the Tauranga Harbour and Waihi Estuary catchments and the Ministry of Fisheries issues customary harvesting permits on a frequent basis throughout the year.
Illness
Two or more linked cases of gastro-intestinal illness are notifiable by medical practitioners to the Medical Officer of Health 7. Notified cases represent a very small proportion of the overall burden of gastro-intestinal illness in New Zealand. A recent study 8 carried out by the Institute of Environmental Science and Research (ESR) compared notification records and general practitioner records with telephone household interviews to estimate the percentage of people with acute gastrointestinal illness who visit a general practitioner, have faecal specimens taken, and are then notified to the Medical Officer of Health if a causative organism is found. This study was conducted throughout New Zealand and included the Bay of Plenty region. In summary the study found that of people with Acute Gastrointestinal Illness (AGI), 22% visit a general practitioner, 8% have a faecal specimen taken, 1.6% test positive for a causative organism, and 0.5% are notified to the Medical Officer of Health.
The AGI ESR study 9 also found that 9.6% of the Bay of Plenty population experience AGI in any four week period. Australian data estimate that 26-36% of AGI is food- related which means pharmacy visits and medication use will only identify a quarter of food related AGI and presumably an even smaller percentage is likely to relate to shellfish consumption. On this basis pharmacy attendance and use of anti-diarrhoeal sales as a medication is unlikely to represent illness in the community or provide any significant association with expected adverse pollution events. In addition the presence of other confounders such as the timing of increased shellfish consumption
6 New Zealand Food Safety Authority, Review of Non-Commercial Wild Food in New Zealand, Environmental Science and Research Report, July 2005. 7 Section 74, Health Act 1956 8 Environmental Science and Research, Acute Gastrointestinal Illness (AGI) Study, Final Study Report, August 2007. 9 Environmental Science and Research, Acute Gastrointestinal Illness (AGI) Study, Final Study Report, August 2007.
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 21 such as with a hui or tangi may contribute to increased AGI but these events would be difficult to account for.
Information pertaining to the number of disease outbreaks and cases of gastro- intestinal disease which includes norovirus within the community of the project catchment area was collated. Non-commercial shellfish gathered from the study area was not identified as a cause of the disease outbreaks notified, but nevertheless indicates which diseases is present in the population of the study catchment areas.
It is recognised that norovirus infections may be particularly susceptible to under- reporting because usually symptoms are self-limiting within 24 hours of onset and most people will not go to the doctor. If they do go to the doctor, faecal specimens that could be used to diagnose gastrointestinal illness may not be taken until symptoms have been present for some days. By then the symptoms will usually have ceased. Not all faecal specimens are screened for norovirus.
Table 6: Outbreaks of disease notified to the Medical Officer of Health, in the Bay of Plenty district from October 2007 to October 2008.
Disease Report Date Total number of cases incl. probable Salmonella 19/10/07 85 Gastroenteritis 05/11/07 4 Norovirus 14/11/07 7 Norovirus 11/12/07 28 Norovirus 12/12/07 21 Giardia 12/12/07 3 Norovirus 13/12/07 4 Norovirus 20/12/07 13 Salmonella 22/01/08 6 Gastroenteritis 30/01/08 15 Norovirus 04/02/08 26 Gastroenteritis 02/05/08 9 Norovirus 05/05/08 31 Gastroenteritis 19/06/08 9 Norovirus 28/07/08 33 Gastroenteritis 31/07/08 9 Norovirus 18/09/08 18
Feral shellfish, where the species has not been recorded, were the suspected cause of 14 cases of gastroenteritis (seven campylobacteriosis, four salmonellosis, yersiniosis, giardiasis and typhoid) between 1997 and August 2004 for New Zealand. All other cases where a certain species of shellfish has been named as the possible vehicle of transmission are listed in Table 7
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 22
Table 7: Number of cases of gastroenteritis between 1997 and 2004 where shellfish was suspected as being the causative agent.
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 23 Monthly Surveillance Results
A total of 7 sites were sampled in the surveillance study. Due to the lack of availability of horse mussels from the Te Puna - Waipa Rd site after April 2008 an alternative sample site at the Waikareao Entrance by Marine Park was used from May 2008. Over the year 72 shellfish samples were collected tested for E. coli , Enterococci, Faecal Coliforms, Noroviruses and Adenoviruses.
Indicator Bacteria Results for Shellfish
Faecal indicator bacteria were detected in all shellfish samples.
Table 8 shows the distribution of indicator bacteria concentrations found in shellfish from monthly sampling over a 12 month period (2007/2008). Oysters from Te Puna Estuary had the highest results for thermo-tolerant indicator bacteria ( E. coli and faecal coliforms) apart from one high faecal coliform result at Pios Beach. Enterococci were the highest in cockles from the Waikareao entrance followed by cockles from Pios Beach. Overall pipi from Tilby Point and opposite Pilot Bay had the lowest mean and median results over the 12 months.
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 24 Table 8: Statistics for Indicator bacteria results in shellfish over the 12 month survey, 2007 to 2008 (sites ranked by median). E.coli (MPN/100g) Valid Mean Median Minimum Maximum Percentile Percentile N10 - 10 - 90 Opposite Pilot Bay - Pipi 12 91 11 1 500 1 500 Tilby Point - Pipi 12 62 29 1 240 1 240 Te Puna - Horse Mussel 7 97 80 2 240 2 240 Waihi Estuary - Pipi 12 357 105 4 2100 4 2100 Waikareao entrance - 5 156 130 2 300 2 300 Cockle Pios Beach - Cockle 12 340 130 1 3000 1 3000 Te Puna Estuary - Oyster 12 1108 130 4 5000 4 5000
Faecal coliforms (MPN/100g) Valid N Mean Median Minimum Maximum Percentile Percentile - 10 - 90 Opposite Pilot Bay - Pipi 12 562 27 1 3000 1 1600 Tilby Point - Pipi 12 146 45 2 500 4 500 Te Puna - Horse Mussel 7 132 170 2 240 2 240 Pios Beach - Cockle 12 1782 185 13 17000 30 2700 Waihi Estuary - Pipi 12 410 235 20 2100 80 900 Waikareao entrance - 5 352 240 80 700 80 700 Cockle Te Puna Estuary - Oyster 12 2072 850 140 9000 170 5000
Enterococci (MPN/100g) Valid N Mean Median Minimum Maximum Percentile Percentile - 10 - 95 Te Puna - Horse Mussel 7 48 20 1 140 2 240 Opposite Pilot Bay - Pipi 12 131 35 4 900 1 1600 Tilby Point - Pipi 12 64 39 4 300 4 500 Te Puna Estuary - Oyster 12 841 115 11 5000 170 5000 Waihi Estuary - Pipi 12 253 135 17 900 80 900 Waikareao entrance - 5 842 230 50 2400 80 700 Cockle Pios Beach - Cockle 12 1088 380 19 7000 30 2700
Viral Results for Shellfish
The overall norovirus and adenovirus surveillance results from monthly sampling of shellfish from the 7 sites across the region are shown in Figure 2. Adenovirus results were all below the level of quantitation for the detection method used in the study and so no data on numbers of adenoviruses present in shellfish is available. novirus results were all below the level of quantitation for our detection method so we cannot make an yfurther comments on the levels present in the shellfish.
Over the year 72 shellfish samples were collected and noroviruses were detected in 23 (32%) of these. Adenoviruses were only detected on 7 of the 72 sampling occasions (9.7%) during the surveillance study (Figure 2, Table 9). The overall norovirus and adenovirus surveillance results from monthly sampling of shellfish from the 7 sites across the region are shown in Figure 2. Over the year 72 shellfish samples were collected and noroviruses were detected in 23 (32%) of these.
10 Valid N = number of samples
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 25 Adenoviruses were only detected on 7 of the 72 sampling occasions (9.7%) during the surveillance study (Figure 2, Table 9).
Figure 2: Number of Shellfish Samples Positive for Norovirus and Adenovirus
Waikareao Entrance
Waihi Estuary-Little Waihi
Tilby Point, Otumoetai
Te Puna -Waipa Rd
Te Puna Estuary
Pios Beach
Pilot Bay Total samples Norovirus positive 0 2 4 6 8 10 12 14 Adenovirus positive No. of samples
Table 9 shows the overall occurrence of GI and GII norovirus and adenovirus in shellfish from each site through the year. Noroviruses were detected in shellfish samples from one or more sites every month except in January 2008.
Table 9: Virus results in all shellfish sampled monthly over 12 months.
Norovirus GI Norovirus GII Adenovirus
Total No of Tests 72 72 72 No. of Positive 3 23 7 % Positive 4.2% 32% 9.7%
GI Norovirus strains were only detected on 3 of 72 occasions (4.2%), twice in pipi from the site opposite Pilot Bay and once in cockles from the site at the Waikareao Entrance. GI Norovirus strains always occurred with GII noroviruses. GII Norovirus strains were detected in samples of pipi, cockles and horse mussels on 23 of the 72 sampling occasions (32%) during the surveillance period. The site which was most frequently contaminated with norovirus was offshore between Tilby Point and Otumoetai, Tauranga Harbour. Norovirus was not detected in oysters collected from Te Puna Estuary during the study. All sites except Te Puna – Te Puna Road were positive for adenovirus on at least one occasion.
Noroviruses were detected in shellfish samples from one or more sites every month except in January 2008 (see Appendix 3). Pipi collected from Tilby Point were contaminated with GII norovirus 9 out of 12 occasions (75%), and were negative for noroviruses in January, April and September 2008. In February 2008 all sites except Te Puna Estuary were positive for GII norovirus. GI Norovirus was only detected in February, June and July 2008. Adenovirus was detected in February, April, June
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 26 and September 2008. In all monthly shellfish samples where norovirus and adenovirus were detected, the virus levels were classed as low (i.e. < 80 RTPCRU/g of gut tissue). Te Puna Estuary was negative for norovirus at all times.
Indicator Bacteria Results for Shellfish Adjacent Water
Indicator bacteria results are shown in Figures 3 and 4 based on their geographic location. In the north Tauranga Harbour basin all indicator bacteria concentrations tend to increase to the south around Ongare and Kauri Points. There were some elevated E. coli and faecal coliforms results at Bowentown boat ramp (Pios Beach) due to a few elevated results as shown in the box-whisker plots.
Figure 3: Indicator bacteria concentrations Tauranga Harbour, October 2007 to September 2008.
North Tauranga Harbour South Tauranga Harbour
Median 10%-90% Min-Max Median 10%-90% Min-Max Guideline for shellfish waters Guideline for shellfish waters 350 450
300 400
350 250
300 200 250 150 200
100 Faecal coliforms (cfu/100ml) coliforms Faecal 150 FaecalColiforms (cfu/100ml) 50 100
0 50 Bowntown Boat Ramp Ongare Point Tanners Point Kauri Point Jetty 0 Pahoia Te Puna Marina Pilot Bay Omokoroa Otumoetai Waipu Maungatapu North Tauranga Harbour South Tauranga Harbour
Median 10%-90% Min-Max Median 10%-90% Min-Max
350 350
300 300
250 250
200 200
150 150 E.coli(cfu/100ml)
100 E.coli (cfu/100ml) 100 50
50 0 Bowntown Boat Ramp Ongare Point Tanners Point Kauri Point Jetty 0 Pahoia Te Puna Marina Pilot Bay Omokoroa Otumoetai Waipu Maungatapu
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 27 North Tauraunga Harbour South Tauraunga Harbour Median 10%-90% Min-Max Median 10%-90% Min-Max 350 350 1000
300 300
250 250
200 200
150 150
100 Enterococci (cfu/100ml) Enterococci (cfu/100ml) 100 50
50 0 Bowntown Boat Ramp Ongare Point Tanners Point Kauri Point 0 Pahoia Te Puna Marina Pilot Bay Omokoroa Otumoetai Waipu Maungatapu
Indicator bacteria results for the South Tauranga Harbour have a similar pattern to the north, generally becoming more concentrated deeper into the estuary. The Wairoa River is also likely to have an influence over those sites in closest proximity (Te Puna and Otumoetai) and on the deeper reaches of the estuary such as Pahoia.
The highest median results over the 12 months of sampling for all three bacterial indicators were at Waihi Estuary. This is likely to reflect the influence of the Pongakawa River and other freshwater inflows in the estuary.
Figure 4: Indicator bacteria concentrations Waihi Estuary, October 2007 to September 2008.
Waihi Estuary
Median 10%-90% Min-Max FC Guideline for shellfish waters 250
200
150 cfu/100ml 100
50
0 FC E.coli Ent
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 28 Adverse Pollution Event Results
Sewage Overflow Event
The first adverse event, a point source sewage discharge, occurred in February 2008. This event was the only sewage overflow discharge over the threshold set by Tauranga City Council that occurred during the study period. The threshold was designed to capture an above average sewage discharge and was based on the average volume of sewage discharged from the number of sewage overflow events that had occurred in the year previously. The sewage overflow event was caused by a pipe splitting under pressure from a settling retaining wall. A total twenty sewage overflows occurred during the study period. Excluding this event the remaining overflows were minor in terms of the volume of sewage discharged (Appendix 10).
The point source sewage discharge event was first identified on February 16 2008, but is believed to have commenced earlier in February. Shellfish were collected from sites located 50 m and 500m from the point source and from 2 regular monitoring sites on the same day that the sewage overflow was detected, then 2 days and 7 days later. Further samples were then taken 14, 28 and 50 days following the event. A final sample was taken from the site 50m from the overflow after 87 days (12.4 weeks). A seawater sample was also collected on 19 February from close to the discharge site. No further sewage discharge events meeting the adverse pollution event criteria were recorded during the study.
Indicator Bacteria Results for Shellfish
Initial indicator bacteria results sampled in close proximity to the source of sewage contamination (within 50 m and 500 m) displayed an initial decrease after 2 days (Figure 5). This was followed by a further increase in bacterial counts after one week at these sites which may be due to an intense rainfall event. However, rainfall doesn’t explain why concentrations were above the safe consumption guideline criteria 50 days after the event. What may explain these results is the occurrence of an illegal stormwater discharge from a local offal processing site at this time. Indicator bacteria results after 80 days for the 50 m and 500 m sites were low, well within safe consumption bacterial guideline criteria.
An increase in faecal coliforms and E.coli concentrations at Tilby Point and Pilot Bay, occurred 7 days after the event. However, enterococci decreased at Tilby Pont and remained at low concentrations while at Pilot Bay enterococci increased two weeks after the event, otherwise the same pattern of results as Tilby Point was seen. It is possible that the initial rise in concentrations of indicator bacteria in shellfish at these sites are a result of the sewage spill, but based on indicator bacteria results alone this cannot be conclusive.
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 29 Figure 5 Indicator bacteria concentrations in shellfish for 4 sites, Tauranga Harbour.
Sew age Overflow Event 100000
10000
1000
100
10 E.coli (MPN/100g) E.coli 1 12-Feb-08 22-Feb-08 3-Mar-08 13-Mar-08 23-Mar-08 2-Apr-08 12-Apr-08
Anchorage Grove - 50m Anchorage Grove - 500m Opposite Pilot Bay Tilby Point Shellfish criteria
Sew age Overflow Event 100000
10000
1000
100
10
1
Faecal coliform Faecal (MPN/100g) 12-Feb-08 22-Feb-08 3-Mar-08 13-Mar-08 23-Mar-08 2-Apr-08 12-Apr-08
Anchorage Grove - 50m Anchorage Grove - 500m Opposite Pilot Bay Tilby Point Shellfish criteria
Sew age Overflow Event
100000
10000
1000
100
10
Enterococci (MPN/100g) Enterococci 1 12-Feb-08 22-Feb-08 3-Mar-08 13-Mar-08 23-Mar-08 2-Apr-08 12-Apr-08
Anchorage Grove - 50m Anchorage Grove - 500m Opposite Pilot Bay Tilby Point
Viral Results for Shellfish
A total of 25 samples were collected between 19 February and 15 May 2008 following the sewage spill event. Of these, 19 (76%) were positive for norovirus and 5 (20%) for adenovirus. GII noroviruses were detected in shellfish from Tilby Point for up to 2 months and from the Pilot Bay site for over 4 months but no GI noroviruses were detected from these 2 sites following the discharge. Virus levels were low in these samples throughout the study. In contrast, two additional sampling sites close to the discharge were consistently positive with high levels of both GI and GII norovirus over the next 1-2 months. Shellfish collected from the 50m Anchorage Grove site closest to the spill were all norovirus positive for the following 3 months, with high levels of norovirus observed in 2 of the 7 samples collected (Figure 6a).
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 30 The 500m Anchorage Grove site was norovirus-positive over 1 month and within this period moderate and high norovirus levels were observed (Figures 6b & 6c).
Figure 6a shows the occurrence of norovirus in shellfish samples from each site over several months. The effects of the adverse events in February and April/May show an increase in norovirus detection across most sites. Additional samples were collected from Pilot Bay and Tilby Point during and after the February 2008 discharge event, and from all sites following the rainfall event in April 2008.
Figure 6a: Norovirus occurrence and levels in shellfish samples following sewage overflow event (N=25).
Tilby Point, Otumoetai
Pilot Bay
500M NE Anchorage Gr
50M end Anchorage Gr
Not detected Positive0 (low) 1 2 3 4 5 6 7 8 Positive (mod) Positive (high) No. of samples Positive (v high)
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 31 Figure 6b Norovirus GI levels (Log 10 RTPCRU/g of shellfish gut tissue) in shellfish following sewage overflow event
4.0 50M end Anchorage Dr 3.5 500M NE Anchorage Dr Pilot Bay 3.0 Tilby Point 2.5
2.0
1.5
Log10 NoV GILog10 RTPCRU/g 1.0
0.5
0.0 19.02.08 21.02.08 25.02.08 4.03.08 18.03.08 8.04.08 15.05.08 Collection date
Figure 6c Norovirus GII levels (Log 10 RTPCRU/g of shellfish gut tissue) in shellfish following sewage overflow event
3.5 50m end Anchorage Gr 3.0 500m NE Anchorage Gr
2.5 Pilot Bay Tilby Point 2.0
1.5
1.0 Log10 NoVGII RTPCRU/g 0.5
0.0 19.02.08 21.02.08 25.02.08 4.03.08 18.03.08 8.04.08 15.05.08 Collection date
The occurrence of different F-RNA phage genogroups and norovirus in shellfish following the sewage overflow event is shown in Figure 7.
An association was observed between the occurrence of norovirus and F-RNA phage genogroups II and III, which are associated with human faecal pollution, in shellfish. No F-RNA phage were detected in norovirus-negative samples from 50m and 500m Anchorage Grove sites close to the spill, but 11 of the 12 (91.7%) norovirus-positive
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 32 samples were also positive for human–associated F-RNA phage genogroup II from these 2 sites. Two of these samples were also positive for human associated F-RNA genogroup III. Animal-associated F-RNA genogroup I phage were detected in two shellfish samples from the 50m Anchorage Grove site, both of which were positive for norovirus GII and also human-associated F-RNA phage genogroup II.
Positive results for human–associated F-RNA phage genogroup II were also detected in shellfish three times at Pilot Bay and once at Tilby Point.
Figure 7: Occurrence of norovirus (NoV) and F-RNA phage genogroups in shellfish following point source sewage pollution event (N=25)
4
3
2 No. No. of samples 1
0 Neg Pos GI Pos GII, GIII Neg Pos GI, GII Pos GII Pos GII, GIII
NoV Neg NoV Pos
500M Anchorage Gr 50M Anchorage Gr Opposite Pilot Bay Tilby Point
Rainfall Event
The second pollution event resulted following heavy rainfall in the region.
An adverse rainfall event was triggered for sampling by the Wairoa River flow exceeding 200 m 3/s (median flow = 11.14 m 3/s). The event occurred 15 April 2008 with the first shellfish sampling occurring 17 April 2008 (day 1). Subsequent shellfish samples were collected from the 6 study sampling sites at 1, 2, 5, 7, 15, 21, 28 and 35 days after the initial rainfall event. Full results are listed in Appendix 5.
This event was followed by further heavy rainfall on May 1 2008. After the main rainfall trigger event on 15 th April several smaller events followed potentially extending the period of shellfish contamination.
Indicator Bacterial Results for Shellfish
Figure 8 and 9 display shellfish indicator bacteria concentrations and the rainfall experienced down the Western Bay of Plenty from Tuapiro in the north to Pongakawa in the Waihi Estuary catchment.
After the main event faecal coliform and E. coli concentrations in shellfish returned to levels safe or near safe for consumption (based on indicator bacteria criteria) at Pios Beach, Tilby Point, opposite Pilot Bay, and Te Puna Estuary within 7 days.
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 33 Enterococci concentrations in shellfish at Pios Beach also showed a decline after the initial rainfall event, as did Tilby Point and opposite Pilots Bay. At Te Puna Estuary enterococci concentrations increased 5 days after the event but showed a decrease after 7 days (Figure 9).
The initial event rainfall the Waihi Estuary catchment took longer to abate than that around Tauranga Harbour. Hence faecal coliform and E. coli concentrations were still rising on the second day of sampling. However while these two indicator bacteria species declined on day 5 of sampling they increased again on day 7. Enterococci concentrations almost responded in the opposite manner with no obvious decline after rainfall had abated (Figure 8). This may be due to the longevity of enterococci than other thermo-tolerant bacterial indicators.
Figure 8: Indicator bacteria concentrations in shellfish and total daily rainfall over a rainfall event, North Tauranga Harbour and Waihi Estuary.
North Tauranga Harbour
100000 120
10000 100 80 1000 60 100 40 Rainfall(mm) 10 20 MPN/100ml 1 0
4 4 4 4 4 5 5 5 5 5 5 5 5 5 0 /04 0 /04 0 /04 0 /04 0 /04 /0 0 /0 /0 /05 0 /05 0 /05 0 /05 0 /05 0 /05 1/ 5/ 9/ 3/ 7/ 1 3/ 5 7/05 9 3/ 7/ 1/ 5/ 9/ 1 13 1 17 1 21 2 25 2 29 11 1 15 1 19 2 23 2 27 2 31
Tuapiro Rainfall Faecal coliforms E.coli Enterococci shellfish criteria (FC & E.coli)
Waihi Estuary
100000 80 70 10000 60 1000 50 40 100 30
20 Rainfall(mm) 10
MPN/100ml 10 1 0
4 4 4 4 4 4 4 5 5 5 5 5 5 5 5 5 /0 /0 0 /0 /0 0 /0 /0 /05 0 /0 0 /0 0 /0 5 7 1/ 3 5 9/ 1 3/05 5/05 7 9 3/ 5 1/ 3 9/ 1 11/0 13/04 1 1 19/04 2 2 2 27/04 2 11/05 1 1 17/05 19/05 2 2 25/0 27/05 2 3
Pongakawa Rainfall Faecal coliforms E.coli Enterococci shellfish criteria (FC & E.coli)
Rain events subsequent to the trigger event do appear to have impacted bacterial concentrations at a number of sites. All indicator bacteria in shellfish sampled at Pios Beach in the north of Tauranga Harbour increased as the smaller rain events occurred. However, within four days of the last minor event all shellfish at Pios Beach had indicator bacteria levels less than 230 MPN/100g (Figure 8). Six days later at Pios Beach, and two days after ten millimetres of rain E. coli levels continued to drop in the shellfish although faecal coliform levels had increased. Enterococci levels remained at a similar concentration.
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 34 At Waihi Estuary the smaller rainfall events showed less consistent results, with an initial rise in enterococci and faecal coliforms following the next smaller event, but almost no E. coli were detected. Six days later after more rainfall in the catchment, enterococci and faecal coliforms numbers dropped but E. coli numbers increased equal to faecal coliforms. Rainfall had only a small impact on the overall flow (figure 10) of the Pongakawa River (the main freshwater inflow to the Waihi Estuary) although the small increases in flow that occurred correspond to fluctuating indicator bacterial levels apart from the very low E.coli concentrations found on the 1 May 2008. However, nine days after another strong flow generating event (10 May 2008) only E.coli and enterococci concentrations decreased.
Figure 9: Indicator bacteria concentrations in shellfish and total daily rainfall over a rainfall event, South Tauranga Harbour.
South Tauranga Harbour
10000 120 100 1000 80 100 60 40
10 Rainfall(mm) 20
(MPN/100ml) 1 0 Faecalcoliforms 4 4 4 4 4 4 5 5 5 5 5 5 5 5 5 /0 /0 /0 0 /0 /05 0 /05 /0 /05 /0 /0 /05 /0 3 5 3 1/ 3 5 7/05 9/ 1 3 1 3 1 11/04 1 1 17/0 19/04 21/04 2 25/0 27/0 29/04 1 1 15/0 17/05 19 2 2 25/0 27/05 29 3
Waimapu Rainfall Waipapa Rainfall Te Puna - Waipa Road Te Puna Estuary Tilby Point Waikareao Entrance Opposite Pilot Bay Shellfish criteria
South Tauranga Harbour
10000 120 100 1000 80 100 60 40
10 Rainfall(mm)
E.coli(MPN/100ml) 20 1 0
4 4 4 4 4 4 4 5 5 5 5 5 5 5 5 /0 /0 /04 /04 0 0 0 /0 /0 /0 /05 /05 /0 /0 /05 0 0 /0 /0 /05 1 3 5 7 7 9 1 3 5 7/05 9/0 1 3 5 7/05 9/05 7 9 1 1 1 1 1 19/04 21/ 23/ 25/ 2 2 1 1 1 1 1 21/05 23/ 25/ 2 2 3
Waimapu Rainfall Waipapa Rainfall Te Puna - Waipa Road Te Puna Estuary Tilby Point Waikareao Entrance Opposite Pilot Bay Shellfish criteria
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 35 South Tauranga Harbour
10000 120
100 1000 80
100 60 40 Enterococci (MPN/100ml) 10 Rainfall(mm) 20 1 0
4 4 4 4 4 5 5 5 5 5 5 5 /04 /04 /0 /0 /0 /05 /05 /05 0 /05 /05 /0 /0 /05 /0 /0 1 3 5 7 9 1 3 5 7/05 9/ 3 5 7 7 9 1 1 1 1 17/0 19/0 21/04 23/04 25/04 2 2 11 1 1 1 19/0 21/0 23/05 25/05 2 2 3 Waimapu Rainfall Waipapa Rainfall Te Puna - Waipa Road Te Puna Estuary
Tilby Point Waikareao Entrance Opposite Pilot Bay
Figure 10: Indicator bacteria concentrations in shellfish, Waihi Estuary and total daily flow Pongakawa River.
Waihi Estuary
100000 7.5 7 10000 6.5 1000 6 100 5.5
` 5 Flow (m3/s) 10 4.5 MPN/100ml 1 4
04 /05 05 1/05 3/05 5 7/05 9/05 11/ 13/04 15/04 17/04 19/04 21/04 23/04 25/04 27/04 29/04 11/05 13/05 15/05 17/05 19/05 21/05 23/ 25/05 27/05 29/05 31/05
Faecal coliforms E.coli Enterococci shellfish criteria (FC & E.coli) Pongakawa Flow
E. coli and faecal coliform concentrations in South Tauranga shellfish (Figure 9) appear to be the indicator species that are most sensitive to the changes in freshwater inflows (as measured by rainfall and river flow). For E. coli , all but one sample from opposite Pilot Bay from the three sites consistently monitored in South Tauranga Harbour registered the impact of increased freshwater inflows (Figure 9). Faecal coliform concentrations were more consistent with fluctuations in freshwater inflows as is demonstrated in Figure 12, where concentrations are graphed against flow from the Wairoa River, the largest freshwater input in the South Tauranga Harbour. The exception being the last sample from event monitoring (21 May 2008) where faecal coliform concentrations rose.
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 36 Figure 11: Faecal coliform concentrations in shellfish at 5 sites, South Tauranga Harbour and Wairoa River daily total flow.
South Tauranga Harbour
10000 140 120 1000 100 /s) 80 3 100 60
10 40 Flow (m 20
(MPN/100ml) 1 0 Faecal coliforms 4 5 5 04 0 04 04 05 05 05 0 05 0 9/ 1/05 3/05 5/ 7/05 9/05 1/ 11/04 13/04 15/ 17/ 19/04 21/04 23/ 25/04 27/04 2 11/05 13/05 15/ 17/05 19/05 2 23/ 25/05 27/05 29/ 31/
Te Puna - Waipa Road Te Puna Estuary Tilby Point Waikareao Entrance Opposite Pilot Bay Shellfish criteria Wairoa River flow
Shellfish at Waikareao Estuary entrance were not sampled until five days after the trigger event (Figure 9). If it is assumed that indicator bacteria levels were similar to those found in other shellfish species over the first two days after the trigger event then decreases in indicator bacteria have occurred post the event. Faecal coliform concentrations at this site do remain higher than other sites. This may be a function of several factors: shellfish species filtration rate (cockle vs pipi vs oyster); substrate type; and influence of inflow from the Kopurererua Stream as well as the Wairoa River.
Viral Results for Shellfish
The norovirus levels detected in shellfish following the rainfall event were consistently low compared with the sewage spill event where higher levels were detected on 4/19 occasions. No clear relationship with norovirus presence was observed for the rainfall event.
Following the rainfall event in April/ May 2008, 49 shellfish samples were collected on 8 occasions over the 4 week period from 17 April to 21 May 2008. Of these, 13 (26.5%) showed presence of low levels of norovirus, and 4 (8.2%) were positive for adenovirus. No norovirus were detected in shellfish from 3 sites, Waihi Estuary, Te Puna – Waipa Rd and Te Puna Estuary. Only 1 sample from Pios Beach was positive for norovirus. Urban sites at Tilby Point (3), Pilot Bay (5) and Waikareao Entrance (4) were most frequently positive for norovirus following the rainfall events.
Pilot Bay and Waikaeareo entrance were both still positive for norovirus more than 28 days after the event and Tilby Point was still positive for norovirus more than 14 days later.
Adenoviruses were detected in shellfish from Tilby Point (2), Pilot Bay (1) and Waikareao Entrance (1).
Phage genogroups I and IV are associated with animal pollution and genogroups II and III are frequently from human sources but may also be associated with animals.
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 37 Table 10 shows the distribution of virus and phage across the sites following the event sampling. It is clear that the human viruses (noroviruses and adenoviruses) occur mainly in shellfish from the urban sites.
Table 10: Percent Positive Virus and FRNA Bacteriophage Results over Rain Event Sampling (n=8, n=7 for Waikareao).
Norovirus GI Norovirus Adenovirus FRNA GI FRNA FRNA FRNA GII GII GIII GIV Human Human Human Animal Human Human Animal Te Puna 0% 0% 0% 50% 62.5% 12.5% 0% Estuary Tilby Point 0% 37.5% 25% 62.5% 75% 0% 0% Waikareao 0% 57.1% 0% 71.4% 100% 0% 0% Entrance Opposite Pilot 12.5% 62.5% 12.5% 12.5% 25% 12.5% 0% Bay Pios Beach 0% 12.5% 0% 37.5% 62.5% 37.5% 0% Waihi Estuary 0% 0% 0% 37.5% 75% 0% 0%
Virus results are listed in Appendix 5. Norovirus GII was the most prevalent viral species over the sampling period (35 days) with 25.6 percent of the samples positive. Norovirus was detected in samples from predominantly three sites in South Tauranga Harbour with one positive sample from Pios Beach. Norovirus was detected in the same sites as the monthly sampling sites. During the rainfall event the number of norovirus positive samples was lower than expected.
The percentage of GII norovirus positive shellfish samples was much lower over the rainfall events compared with monthly results over the year (25.6% versus 47.2%).
The occurrence of different F-RNA phage genogroups and norovirus in shellfish following the rainfall event is also shown in Figure 12. Thirty eight (77.5%) rainfall event samples were positive for F-RNA phage, and of these, 17 contained mixtures of human and animal – associated phage genogroups I, II and III.
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 38 Figure 12: Occurrence of norovirus (NoV) and F-RNA phage genogroups in shellfish samples following adverse rain event (n=49)
4 Pilot Bay Pios Beach Te Puna Estuary Tilby Point 3 Waihi Estuary-Little Waihi Waikareao Entrance Te Puna-Waipa Rd
2 No. of samples of No.
1
0 Neg Pos GI Pos GI, GII Pos GI, GII, Pos GII Pos GII, GIII Neg Pos GI Pos GI, GII Pos GII Pos GII, GIII GIII
NoV Neg NoV Pos
Discussion on Sewage Overflow & Rainfall Event Results
Indicator Bacterial Results for Shellfish
Comparison of indicator bacteria data taken after the rain event and sewage contamination event are not necessarily measuring the same impacts as one event is from a non-point source, the other from a point source. However, in this survey shellfish bacterial concentrations measured at the site opposite Pilot Bay provides some insight to the potential impacts of contamination from these two different.
The site opposite Pilot Bay is approximately 8 kilometres from the sewage leak and a similar distance from the mouth of the Wairoa River, the largest freshwater input to the southern end of the harbour. As demonstrated in Figure 13, faecal coliform and E. coli concentrations are initially low for two days after the discovery of the sewage leak. After 7 days the concentrations rise but this coincides with a smaller rain event. For all these indicator bacteria species, after the rain event there is an initial high concentration of bacteria followed by decreasing concentrations in the first week. A small rise occurs in the rain event data after one week as more rain is experienced (Figure 13).
These observations show that faecal coliforms and E. coli may not have any impact on a site several kilometres away from the point of discharge. Enterococci may however provide a better indication of any potential impact of sewage spills on more distant shellfish beds, where generally E. coli and/or faecal coliforms are better indicators of contamination after rainfall (see Adverse Rainfall Event section).
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 39
Figure 13: Indicator bacteria concentrations in shellfish after a major rain event and sewage contamination event, Opposite Pilot Bay.
10000 10000
1000 1000
100 100 E.coli (MPN/100g) E.coli 10 10 Faecal coliforms (MPN/100g) coliforms Faecal
1 1 0 10 20 30 40 0 10 20 30 40 No. of days since event No. of days since event
Rain Sew age Rain Sew age
10000
1000
100
10 Enterococci (MPN/100g) Enterococci
1 0 10 20 30 40 No. of days since event
Rain Sew age
Viral Results for Shellfish
Norovirus
A total of 74 samples were collected following 2 adverse pollution events which met the specified criteria. As shown in Table 11, there was a clear difference in the presence of norovirus in shellfish following the sewage discharge event compared with the rainfall event. This is to be expected as the faecal pollution from a sewage spill would be of greater magnitude than a rainfall event where the pollution results more from storm water overflows and so is diluted and more diffuse.
Table 11: Presence of norovirus in shellfish samples following adverse pollution events
Adverse event Norovirus negative Norovirus positive Total Point source sewage discharge 6 (24.0%) 19 (76.0%) 25 Rainfall 36 (73.5%) 13 (26.5%) 49 Total 42 32 74
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 40 F-RNA phage
F-RNA phage was commonly identified in shellfish following both adverse pollution events. Figure 14 shows the overall results for occurrence of norovirus and F-RNA phage from both adverse events.
Following the respective adverse pollution events, 16/25 (64.0%) sewage discharge event shellfish samples and 38/49 (77.5%) rainfall event shellfish samples were positive for F-RNA phage. Human-associated F-RNA phage genogroups II and III were commonly identified in samples following both the point source event (15/25, 60%) and the rainfall event (32/49, 65.3%) whereas animal-associated F-RNA phage genogroup I was more commonly detected in shellfish following the rainfall event (22/49, 44.9%) than the point source event (4/25, 16%). No genogroup IV F-RNA phage were detected during the study. The water sample analysed following the sewage discharge was positive for F-RNA phage genogroups I and II.
Figure 14: Comparison between F-RNA phage and norovirus (NoV) occurrence in point source and rainfall adverse event samples (N =74)
Neg F-RNA GI F-RNA GI, GII F-RNA GI, GII, GIII F-RNA GII F-RNA GII, GIII 12
10
8
6
No. of samples of No. 4
2
0 Point source Rainfall Point source Rainfall
NoV negative NoV negative NoV positive NoV positive
The norovirus levels detected in shellfish following the rainfall event were consistently low compared with the sewage spill where higher levels were detected on 4/19 occasions.
F-RNA phage were present in 9 of the13 (69.2%) norovirus-positive rainfall event samples and 14 of the 19 (73.6%) norovirus-positive samples from the sewage spill. However, in contrast to the sewage spill event, F-RNA phage were present in 28 of the 36 (77.8%) norovirus-negative shellfish samples, and no clear relationship with norovirus presence was observed for the rainfall event. The overall virus results for all shellfish samples analysed for viruses, including event samples, are shown in Table 12. Forty nine samples were positive for norovirus (49/137, 35.8%) and fifteen were positive for adenovirus (15/137, 10.9%).
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 41 Table 12: Virus results for shellfish sampled monthly over 12 months (including events).
Norovirus Norovirus Norovirus Adenovirus GI GII GI & GII Total No of Tests 137 137 137 137 No. of Positive 0 36 13 15 % Positive 0 26.3 9.5 10.9
Figure 15 shows the occurrence of norovirus in shellfish samples from each site by month. The effects of the adverse events in February and April/May show an increase in norovirus detection across most sites. Additional samples were collected from Pilot Bay and Tilby Point during and after the February 2008 overflow event, and from all sites following the rainfall event in April 2008.
Figure 15: Norovirus positive samples from each site by month, including event samples (N=37). First event – sewage discharge in February 2008; Second event – rainfall in April-May 2008.
9 8 7 6 5 4 3
NoV positivesamples 2 1 0 8 08 8 8 8 -07 -07 -08 - -0 -0 -08 0 -08 n r r n ul-08 g- ov a J Oct N Dec-07 J Feb Ma Ap May-0 Ju Au Sep Pilot Bay Pios Beach Tilby Point, Otumoetai Waihi Estuary-Little Waihi Waikareao Entrance Te Puna -Waipa Rd Te Puna Estuary
Geographically norovirus in shellfish was most commonly found close to denser urban areas; that is Tauranga City (Figure 16).
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 42 Figure 16: Percentage of positive Norovirus GII results over 12 months monitoring (October 2007 to September 2008). Results for Te Puna Estuary and Waikareao Estuary Entrance are for 7 and 5 months respectively.
% Annual Norovirus GII Positive
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 43 Comparison of Results with Microbiological Limits
Shellfish Adjacent Water Quality
The Microbiological Water Quality Guidelines for Marine and Freshwaters (2003) list recreational shellfish-gathering bacteriological guidelines. These are:
the median faecal coliform content of samples taken over a shellfish-gathering season shall not exceed a Most Probable Number (MPN) of 14/100 mL, and; not more than 10% of samples should exceed an MPN of 43/100 mL (using a five-tube decimal dilution test).
Examining the 12 months of monthly sampling data from sites close to the shellfish harvest areas, Te Puna and Waihi Estuary were above the 14 faecal coliforms/100ml median (Table 13). Only Pilot Bay waters remained within the 10% of samples not exceeding 43 faecal coliforms/100ml for shellfish waters. The highest was Waihi Estuary with almost 42 percent of samples greater than 43 faecal coliforms/100ml.
Table 13: Faecal coliform statistics for shellfish waters, October 2007 to September 2008.
Median n (cfu/100ml) % n > 43 FC cfu/100ml Bowentown Boat Ramp 12 2.0 25.0% Te Puna Beach - Pitua Road 12 18.5 33.3% Otumoetai Beach 12 10.0 16.7% Pilot Bay 12 2.0 8.3% Waihi Domain – Waihi Estuary 12 35.5 41.7%
Shellfish Quality
Although no formal bacterial or viral limits exist for shellfish gathered for non- commercial purposes, NZFSA advise that no norovirus should be present and E. coli levels can be applied as for commercial shellfish. Some caution should be applied in interpretation as the bacterial limits are based on catchment risk assessments and multiple sampling.
For the purposes of the project, a shellfish flesh sample was considered to be fit for human consumption when the following bacteria and virus limits were met.
the E. coli median MPN of the shellfish samples must not exceed 230 E. coli per 100g and not more than 10% of the samples must exceed an MPN of 700 per 100g 11 and; no detectable norovirus genome sequences per gram of gut tissue 12 .
11 NZFSA Animal Products (Specifications for Bivalve Molluscan Shellfish) Notice 2006 12 There are no published standards for norovirus, however in practice a nil tolerance of norovirus genome fragments is applied.
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 44 Bacterial Shellfish Quality
Criteria for E. coli concentrations are shown in Figure 17. Comparison of shellfish results for E. coli with the E. coli criteria show that most shellfish sampled over 12 months complied with the acceptable level, apart from oysters at Te Puna Estuary.
Shellfish species accumulate and release faecal bacteria filtered from surrounding waters at different rates. Oysters are known to accumulate at a faster rate and take longer to release this bacterial loading than other shellfish species. This is likely to explain the higher concentration of E. coli found in Oysters in this study.
Figure 17: E. coli concentrations in bivalves, sampled monthly October 2007 to September 2008 (n=12 except for Waikareao n=5, Te Puna Estuary n=7)
Concentration of E.coli in Shellfish Median 10%-90% Min-Max Bactereriological standards for shellfish 90% Bacteriological standard for shellfish
Waihi Estuary - Pipi
Waikareao entrance - Cockles
Opposite Pilot Bay - Pipi
Tilby Point - Pipi
Te Puna Estuary - Oysters
Te Puna - Horse mussels
PiosPios Beach Beach -- CocklesCockels
5 50 500 5000 MPN/100g
Viral Shellfish Quality
At any time the presence of human norovirus and adenovirus in the environment, including shellfish, is dependent on the levels of virus present in the local community because, as far as we know, people are the main source of these viruses. The human norovirus and adenovirus types detected in our study are not known to infect animals.
In the study most shellfish had virus concentrations below the level of quantification of 80 RTPCRU per gram of shellfish gut tissue, and above the limit of detection (20 RTPCRU/gram) except for samples taken close to the point source sewage discharge where high levels of norovirus were recorded. Reports indicate that the median infectious dose for human norovirus may be as low as 10 virus particles (Teunis et al. 2008), and so this level may have been present in the norovirus - positive shellfish identified in this study. Unfortunately, because norovirus is not
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 45 culturable, it is not possible to relate RTPCRU to infectious norovirus particles unless this data is generated in human dose response studies.
The overall results of the virus sampling over the year found low levels of norovirus present in shellfish from the harbour every month except January, and Adenovirus was infrequently detected in shellfish during the year. Shellfish were below the microbiological limits for the most of the time. This demonstrates that bacterial indicators generally do not show a correlation with viral presence and that shellfish may not be safe to eat even when the bacterial quality is within the accepted limits.
Other Microbiological Criteria
The Food Standard Code Australia New Zealand (2006, Section 1.6.1) and the Ministry of Health Microbiological Reference Criteria for Food (1995) set out criteria for assessing shellfish quality. Both the Food Standards Code and the Reference Criteria are based on the Microbiological Specifications for Foods (ICMSF). The ICMSF Scheme assists with the practical difficulties of representative sampling and interpretation of data provided by the laboratory. It permits some degree of tolerance to compensate for the difficulties of statistical sampling, and non-uniformity of bacterial load.
The Food Standard Code Australia New Zealand (2006, Section 1.6.1)
The Food Standard Code Australia New Zealand (2006, Section 1.6.1) provides bacteriological limits for food which is sold commercially, including shellfish. The criterion for shellfish other than scallops is based on E. coli counts per 100g of flesh in five samples. Shellfish quality is considered to pose a risk to human health when samples are over 230 E. coli per 100g with a tolerance of one sample over 230 E. coli per 100g, but no sample is permitted to be above 700 E. coli per 100g.
Scallops are not included because most consumers remove the gut and cook scallops before consumption, greatly reducing the risk of illness.
Ministry of Health Microbiological Reference Criteria for Food (1995)
The Environment Bay of Plenty Regional Coastal Plan (Schedule Thirteen) sets the criteria for shellfish being unsuitable for human consumption from the Ministry of Health’s (MoH) Microbiological Reference Criteria for Food (1995). Criteria are based on faecal coliform counts per 100g of flesh. Faecal coliform limits have been used historically for shellfish quality assessment but these have been abandoned in recent years in favour of E. coli . This is because faecal coliforms can be derived from non disease causing sources, such as vegetation as well as animal and human waste which can cause disease; where as E. coli indicator bacteria are only present in human and animal waste.
This project analysed shellfish for faecal coliforms. The results have been compared against the Microbiological Reference Criteria for Food to assess shellfish quality for comparison to the New Zealand Food Safety Authority Animal Products (Specifications for Bivalve Molluscan Shellfish) Notice 2006 for commercial shellfish quality used to assess suitability of shellfish for consumption in this study.
Faecal coliform concentrations in the oysters at Te Puna Estuary were above the microbiological reference criteria for food in the majority of samples. This site was
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 46 interesting because no noroviruses were detected in oysters harvested there and adenovirus was only detected once, even though indicator bacterial levels at that site were frequently above the acceptable limit. Therefore the source of pollution at this site is assumed to be from animal rather than human sources.
Pipi opposite Pilot Bay were also often above the faecal coliform criteria, as were and cockles at Pios Beach and cockles at Waikareao Estuary entrance (at around 25 percent). Other sites were generally safe for consumption according to faecal coliform criteria but this could be misleading based on virus results. Pilot Bay and Waikareao Estuary entrance were positive for norovirus on a number of occasions, indicating that pollution there was likely to be of human as well as animal. Although bacterial levels were low Tilby Point was the site most frequently positive for norovirus. This suggests that human pollution was occurring in the area.
Figure 18: Faecal coliform concentrations in bivalves, sampled monthly October 2007 to September 2008 (n=12 except for Waikareao n=5, Te Puna Estuary n=7)
Concentration of Faecal Coliforms in Shellfish Median 10%-90% Min-Max Accetable consumption criteria Unacceptable consumption criteria
Waihi Estuary - Pipi
Waikareao entrance - Cockles
Opposite Pilot Bay - Pipi
Tilby Point - Pipi
Te Puna Estuary - Oysters
Te Puna - Horse mussels
Pios Beach - Cockles
5 50 500 5000 MPN/100g
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 47 Bacteria and Viral Indicators of Contamination
Indicator bacteria concentrations measured over 12 months were variable with some distinct rises and falls only obvious with the more frequent event monitoring undertaken. Enterococci concentrations were generally higher in cockles than other species with oysters next highest on average. Pipi are located in waters generally closer to harbour entrances where sandy substrate is generally found, the greater tidal flushing in these locations is likely to be the cause of the lower enterococci concentrations found at these sites. The thermo-tolerant bacteria ( E. coli and faecal coliforms) concentrations also displayed a gradient in the South Tauranga Harbour sites with the sites closer to the mouth of the harbour generally of lower concentrations than the upper harbour sites. This seems to be the opposite of where the most common norovirus strain was detected.
The most common viral contaminant in shellfish found over the year long survey was the Norovirus GII (30.9% of all samples). GII Norovirus was detected coincident with a wide range of indicator bacterial levels. Indicator bacteria were present all year round at varying levels. Figure 19 displays this range with faecal coliform results for several sites that were periodically found to be positive for Norovirus GII. Table 14 shows that shellfish with the highest median faecal indicator bacterial levels also had the lowest number of positive viral detections. A similar relationship exists between faecal coliform concentrations in shellfish waters and positive norovirus results.
Table 14: Comparison of indicator bacteria and virus results in shellfish and shellfish collecting waters based on monthly sampling over 12 months.
Waters Shellfish FC content Waters E. coli FC GII Norovirus % n > 43 Median Median Median FC MPN/100g MPN/100g cfu/100ml cfu/100ml % Positive Pios Beach - Cockle 2 25% 130 185 25% Te Puna - Horse Mussel 18.5 33% 80 170 29% Te Puna Estuary - Oyster 18.5 33% 130 850 0% Tilby Point - Pipi 10 17% 29 240 67% Waikareao entrance - 130 45 Cockle 10 17% 60% Opposite Pilot Bay - Pipi 2 8% 11 27 50% Waihi Estuary - Pipi 35.5 42% 105 235 8%
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 48 Figure 19: Faecal coliform concentrations in shellfish at selected sites and positive GII norovirus.
Tilby Point Pilot Bay 10000 10000
1000 1000
100 100
10
Faecal coliforms (MPN/100g) coliforms Faecal 10 Faecal coliforms (MPN/100g) coliforms Faecal
1 06/08/07 14/11/07 22/02/08 01/06/08 09/09/08 18/12/08 1 06/08/07 14/11/07 22/02/08 01/06/08 09/09/08 18/12/08 Date Faecal coliform results that Faecal coliform results that are Date Faecal coliform Faecal coliform are Positive for Norovirus Positive for Norovirus
Te Puna Horse Mussels Pios Beach
10000 100000
10000 1000
1000
100 100
10 10 Faecalcoliforms (MPN/100g) Faecalcoliforms (MPN/100g)
1 1 25/09/07 14/11/07 03/01/08 22/02/08 12/04/08 01/06/08 06/08/07 14/11/07 22/02/08 01/06/08 09/09/08 18/12/08 Date Date Faecal coliform results that are Faecal coliform results that Faecal coliform Faecal coliform are Positive for Norovirus Positive for Norovirus
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 49 Discussion
Sources and Pathways of Faecal Contamination
The major factors influencing norovirus occurrence are likely to be the pollution events, of which the two largest occurred in February and April/May 2008. These two events clearly influenced the presence of viruses in monthly samples.
Tilby Point was positive for norovirus on 9 of the 12 sampling occasions during the monthly surveillance period, but there was no obvious source of pollution at this sampling site, which is 300m offshore from a local park. The possible sources of contamination at Tilby Point have been under investigation by city council and regional council staff but to date no definitive causes have been identified. Public toilets are located in the park but are at some distance from the sampling site. No seasonal effect was observed for virus occurrence.
While the origin of a sewage leak or spill is often known, there are multiple sources in the catchment that contribute to faecal contamination. High and low intensity livestock agriculture, avian populations, on-site wastewater treatment systems, marine vessels, meat processing plants, wastewater treatment plants, and leaky sewage infrastructure all have the potential to contribute to contamination of the receiving environment. Unless there is a direct discharge such as occurs with a sewage system overflow, contamination of the estuarine environments predominantly occurs via rivers, streams and stormwater. Table 15 characterises these inputs in terms of catchment statistics.
Human faecal contamination is mainly associated with the urban landscape. The percentage of urban area contained in a catchment highlights the potential risk from this source (Table 15). Denser urban areas have sewage reticulation where sewage is taken to a central treatment plant and, in the case of Tauranga City and Katikati, tertiary treated effluent is discharged to open coast. However, sewage spills and overflows occur and leaky infrastructure and stormwater cross contamination are constant maintenance issues in the urban landscape. Tauranga City Council during the study period has instigated a project to identify where stormwater enters the wastewater system during storm events, with the aim of reducing or eliminating sewage overflows during periods of high rainfall.
Rural communities and isolated rural households treat faecal matter through on-site treatment systems (septic tanks) which have a limited ability to treat pathogenic material. Further treatment is continued with on-site disposal of the effluent to ground. Pathogenic material may enter rivers or streams but how much and the strength of the material depends on the disposal field characteristics, ground water level and proximity of surface water (Sinton, 1982). Several coastal communities with on-site wastewater systems are scattered around the estuaries (Appendix 9), with some of these identified as having a high risk of leaking contaminated effluent to the harbour (Te Puna West, Ongare Point, Tanners Point, Waihi Estuary). Occupied dwelling statistics highlight the potential risk based on the number of dwellings (Table 15); however there are few congregated inland communities and generally dwellings are located greater than 20 m away from surface water conduits to the estuaries. It is the coastal communities that are not reticulated that are likely to present the greater risk of human faecal contamination.
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 50 Discharges from on-site effluent systems in the Bay of Plenty are controlled by the On-Site Effluent Treatment Regional Plan 2006. The plan focuses on areas where discharges from septic tanks are contributing to poor water quality including groundwater and the water margins of lakes, estuaries and shorelines within the region. Advanced on-site effluent treatment systems are required to be installed to improve water quality in specific areas however there are no microbiological limits identified by the plan.
To assist in addressing water quality problems the plan prescribes minimum standards for the design and installation of on-site effluent treatment systems. On- site effluent treatment systems need to be designed and constructed to suit the constraints of the particular site. These constraints include depth to the water table, soil type, soil permeability, size of the land treatment area, slope and the expected volume of discharge. The plan also requires a compulsory maintenance regime in identified communities serviced by septic tanks.
Environment Bay of Plenty does not want to force upgrades for minor failures where reticulated sewage is likely in the foreseeable future. Therefore, Council has reviewed the situation for communities where sewage reticulation is anticipated in the near future.
During the study timeframe Western Bay of Plenty District Council progressively connected the Omokoroa community from septic tanks to Council reticulated sewage system to reduce faecal contamination sources into the Tauranga harbour. In addition, Council is working towards the reticulation of Pukehina, and Little Waihi communities which is expected to be completed by 2012 to assist in reducing human faecal contamination in these areas.
In the shellfish survey, the human faecal contamination markers of norovirus, adenovirus and F-RNA-bacteriophage (GII and GIII) were all found near coastal communities with on-site wastewater treatment. Adenovirus was detected once at Pios Beach, Te Puna and Waihi Estuary, similar to other areas, but detection of the commonly occurring GII norovirus was far less frequent adjacent to these communities. This is unexpected for the Te Puna oysters as these shellfish are in close proximity (across the channel) from several highly contaminated drains, where the contamination is associated with on-site effluent disposal. Human-related genogroups II and III of F-RNA-bacteriophage were found in the Te Puna Estuary oysters over the rain event sampling. These are not exclusive categories but can be used as a guide to the major source of pollution although these genogroups have also occasionally been associated with animal waste (Calci et al., 1998; Havelaar et al., 1990).
Similar results occurred at Pios Beach and Waihi Estuary over the rain event, with Pios Beach recording one positive GII norovirus result, but again FRNA- bacteriophage positive results were often detected over the rain event. It is possible that norovirus was not often present in these communities over the survey period.
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 51 Table 15: Catchment characteristics for potential sources of faecal contamination.
Te Puna South Tauranga North Tauranga Waihi Estuary Estuary Harbour Harbour Catchment size (ha) 2861.8 99166.2 21425.9 32819 % Urban 13 1.2% 5.3% 4.3% 0.2% % Pasture 60% 34.7 36.7% 59.9% No. Dairy 2 42 21 80 Discharges 14 No. Dairy Stock ~380 ~10050 ~2890 ~24060 Occupied Dwellings 15 ~861 ~48400 (40635)^ ~1968 (1470)* ~1098 Major Freshwater Te Puna 640 Wairoa 12100 Tuapiro 1867 Pongakawa 4679 inputs (l/s) Kopurererua 1867 Uretara 890 Kaikokopu 2185 Waimapu 2129 Te Mania 400 Wharere 540 Waipapa 485 TOTAL ~ 4100 TOTAL ~ 7900 TOTAL ~ 17600 Potential risk from Moderate Moderate Moderate High faecal indicator bacteria contamination Potential Risk from Low Moderate Low Low viral contamination ^ Tauranga city occupied dwellings * Katikati occupied dwellings
There is a large potential for contamination of inland surface waters to come from the livestock agriculture in the Bay of Plenty landscape. Statistics New Zealand put livestock numbers in the Bay of Plenty as: 355,000 sheep; 290,000 dairy; 120,000 beef; and 54,000 deer (2008 data). Table 15 shows approximate dairy cow numbers in the respective catchments in this survey.
Comparison of dairy cow numbers to occupied dwellings considering catchment size in the various catchments shown in Table 15 highlights the potential loading from two major faecal sources. The Waihi Estuary site has one of the highest indicator bacterial levels in this survey and yet relatively low virus detection. The lack of positive virus results, even with a number of poorly maintained on-site wastewater treatment systems, suggests the predominant source of indicator bacteria based on catchment characteristics is livestock agriculture. The opposite would seem to hold for the urban sites, Waikareao Estuary and Tilby Point.
There are direct discharges from avian sources and marine vessels but these are difficult to quantify. Surveys are undertaken on some wild fowl species (swan and Canadian geese) and some culling takes place. The wild fowl population remains steady at around 3000 animals on Tauranga Harbour (pers comm . Matthew McDougall, Fish and Game) and the population is relatively mobile. Any estimate of the faecal loading from avian sources would have to include not only waterfowl but also seabird population and terrestrial avian species. This is out of the scope of this survey and is highlighted as an information gap for future work.
Equally any loadings from ocean going vessels are difficult to quantify and pinpoint. For example, Pilot Bay is a popular recreational beach used for swimming and
13 2001 land cover survey. 14 Based on 2009 Environment Bay of Plenty consents data. 15 Statistics New Zealand 2006 census survey.
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 52 boating and faces into the harbour and main shipping channel. There are a number of potential sources of pollution at this site. For Pilot Bay, while it is probable that viral contamination was initially triggered by the sewage contamination event and extended by the autumn winter rainfalls, contamination from marine vessels is also a possibility. The number of vessels moored in any one area may provide a measure of risk of faecal loading from this source, although maritime law prevents untreated sewage to be discharged 500m within shore or in water less than 5 m deep; and treated sewage (by specified system) to be discharged within 100m of a marine farm or mataitai (traditional food collection) (Marine Pollution Regulations). The rate of compliance by vessels to these regulations is not clear and the discharge of chlorine treated effluent is permitted under these regulations, however chlorine is an ineffectual treatment method for protozoa and viruses.
Freshwater inputs to each of the estuaries are similar in relation to the land catchment size. Differences occur with locations of inputs into estuaries, dilution and movement with the tidal cycles, and input characteristics. The survey indicates that indicator bacteria concentrations are stronger at the head of the estuarine basins due to the dynamics of fresh and saline waters mixing and deposition of sediment. Hence the risk of contamination as estimated from faecal indicator bacteria is higher in these locations, although shellfish can be less abundant in these areas.
Potential risk as indicated by bacterial or viral contamination for catchments in the survey is given in Table 15. This does not take into account the risk of contamination from other pathogens such as protozoa. The smallest delineated catchment, Te Puna provides an example of higher levels of faecal indicator bacteria levels associated with waters and shellfish with little viral contamination. In Te Puna Estuary it appears that rural based sources via the freshwater inputs are the primary influencing factor in shellfish contamination. Hence there is a moderate risk as indicated by faecal indicator bacteria and a low risk of viral contamination as none was detected. Conversely, sites dominated by urban landscape would have a higher risk from viral contamination.
Longevity & Extent of Microbiological Contamination
The sewage discharge event provided an excellent example of virus uptake and persistence in shellfish, particularly in shellfish growing close to the source. Shellfish collected 50m from the discharge site were positive for norovirus for approximately 3 months whereas shellfish collected 500m from the site were positive for 1 month only. It is apparent that the higher continuous viral load over time was retained by shellfish for longer. Shellfish from Pilot Bay and Tilby Point, the 2 other sites monitored for this event, were frequently positive for norovirus following the event, but were also norovirus-positive at other times during the study, so the indications are that there were other sources of pollution occurring at these sites.
It is interesting to note that, following the rainfall event, norovirus were less frequently detected than following the sewage discharge event and did not appear to persist for long periods. The levels detected in shellfish following the rainfall event were consistently low compared with the sewage overflow where higher levels were detected on four occasions. Although sample numbers were small, there was a relationship between the occurrence of noroviruses and F-RNA phage in shellfish collected close to the sewage discharge site. No clear relationship was observed following the rainfall event, where many norovirus-negative samples were positive for F-RNA phage.
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 53 Following a sewage pollution event, it is expected that F-RNA phage would be predominantly of human origin, whereas following a rainfall event it is likely that both human and animal F-RNA phage would be present because there would be multiple pollution sources from wastewater and stormwater overflows. This was observed in our study with mixed F-RNA phage populations being detected in the rainfall samples compared with samples from the sewage spill event. These results demonstrate how viral source tracking can assist in determining sources of pollution.
Public Health Risk Assessment
If microbiologically contaminated shellfish are consumed the impact to human health relates to contracting gastroenteritis with vomiting and diarrhoea. This study shows that shellfish in Tauranga harbour and Waihi Estuary are contaminated most of the time and that raw or lightly cooked shellfish may not be safe to eat even when the bacterial quality appears to be within acceptable limits. Consequently, the probability of consuming contaminated shellfish from Tauranga Harbour or Waihi Estuary is high and poses a significant risk to public health. This risk is based on the multiple pathways of microbiological contamination, the large number of people potentially exposed, viral infective dose and attack rate, and the extent and duration of shellfish contamination identified in this study.
The population of the Tauranga district is over 100,000; a further 42,000 people live round the harbour margins within the Western Bay of Plenty District. The population potentially exposed is not limited to those living locally but includes those who come from other districts such as Auckland, Waikato, Rotorua and Turangi to collect and eat local shellfish. Consideration also needs to be given to the population these people come into contact with when unwell. Outbreaks of illness by secondary and tertiary waves of infection from person to person transmission potentially increases the number of people exposed to the risk of ill health.
The areas identified to be regularly contaminated with viruses were those closest to urban areas and these areas are most likely to be accessed by the shellfish gathering population. Gathering is more likely to occur in areas sheltered from adverse weather such as estuarine areas because these areas tend to be more favourable for gathering.
Statistics from Maori households in Northland showed that 11% of the households collected seafood more than once a week, 31% collected at least weekly and 52% at least fortnightly. Harvesting can sometimes increase prior to public holidays and long weekends, particularly by Maori, and is attributed to the preparation for visits from whanau and Marae events (Hay et al. 2000) 16 . There are 26 marae in the catchment of Tauranga Harbour and Waihi Estuary which means there is an increased likelihood of these communities collecting and consuming contaminated shellfish.
Over the study period, norovirus levels were generally low in shellfish except following the point source sewage spill, however the rate for contracting norovirus is high (approximately 50%) and only a few particles are needed to cause symptoms.
High levels of norovirus were detected in shellfish following a sewage pollution event located 50 m from the source and Norovirus was detected in shellfish 50 m from the source for up to 3 months following the sewage pollution event. Although only low levels of norovirus were detected in shellfish from a few sites in the harbour following
16 New Zealand Food Safety Authority, Review of Non-Commercial Wild Food in New Zealand, Environmental Science and Research Report, July 2005.
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 54 a rainfall event, the frequency of sewer overflow and rainfall events is such that shellfish are unlikely to depurate viruses before the next contamination event. This can lengthen the duration of contamination.
Shellfish collected from harbour locations further from the main urban areas of Tauranga and Mount Maunganui were less likely to be positive for viruses. This suggests that the further shellfish are collected from urban areas the lower the risk of gathering virally contaminated shellfish.
The project planned to assess anti-diarrhoeal sales from pharmacies to identify whether a correlation existed between an expected adverse pollution event and Acute Gastrointestinal Illness (AGI) in the community. The criteria and scope around collecting this information was found to be complex and questions arose whether this information would in fact be of value considering the support to the overall project objectives. Pharmacy attendance and use of anti-diarrhoeal sales as a medication was found to be unlikely to represent illness in the community or provide any significant association with expected adverse pollution events. In addition the presence of other confounders such as the timing of increased shellfish consumption such as with a public holiday, hui or tangi may contribute to increased AGI but these events would be difficult to account for.
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 55 Conclusions
Enteric virus contamination of shellfish is occurring in the Tauranga Harbour and Waihi Estuary, and shellfish from a few sites - namely Tilby Point and Pilot Bay, two sites closest to the urban area and main cities of Tauranga and Mount Maunganui, are regularly contaminated with viruses. Over the study period, norovirus levels were generally low in shellfish except following the point source sewage spill.
It can be concluded that there is no distinct relationship between the faecal indicator bacteria and positive viral results. This demonstrates that indicator bacteria may not be reliable indicators of viral contamination in shellfish collected in this survey and vice versa. Similar results have been cited in the literature (e.g. Gerba, 1979; Lees, 2000).
The survey indicates that indicator bacteria concentrations are higher at the head of the estuarine basins due to the dynamics of fresh and saline waters mixing and deposition of sediment. Hence the risk of contamination as estimated from faecal indicator bacteria is higher in these locations, although shellfish can be less abundant in these areas.
The results of this study show that risk of shellfish contamination in estuarine locations can be described by examination of catchment and estuarine characteristics.
Shellfish collected from harbour locations further from the main urban areas of Tauranga and Mount Maunganui were less likely to be positive for viruses, whereas shellfish in estuarine areas dominated by inputs from predominantly rural catchments had higher indicator bacterial levels.
Following a sewage pollution event where mainly human faecal material is discharged, it is expected that the F-RNA phage present would also be predominantly of human origin, whereas following a rainfall event it is likely that there would be multiple pollution sources from wastewater and stormwater overflows containing both human and animal faecal material would be present and that the F- RNA phage would be both animal and human types. These results demonstrate how viral source tracking can assist in determining sources of pollution.
Shellfish were below the microbiological guideline limits (bacterial) for most of the time. Bacterial indicators generally do not show a correlation with viral presence and shellfish may not be safe to eat even when the bacterial quality is within the accepted limits.
Overall this study has demonstrated that enteric virus surveillance combined with microbial source tracking can provide useful information for environmental and public health agencies on the status of their coastal waters and recreational shellfish. The data generated in the study will assist in formulating future management plans for the region.
New Zealand does not have microbiological limits for shellfish gathered for personal consumption. Development of guidelines with a sanitary survey assessment based on catchment risk characteristics would be useful to health authorities and local authorities to carry out their regulatory functions. In the interim, the New Zealand Food Safety Association recommends that the microbiological limits required for commercially-farmed shellfish be applied to recreational shellfish.
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 56 Recommendations
Public health is about keeping people healthy and improving the health of populations the following recommendations are made:
1. Toi Te Ora - Public Health, Tauranga City, Western Bay of Plenty District Councils, and Environment Bay of Plenty should advise the public that there is a significant risk associated with consuming shellfish collected from Tauranga Harbour or Waihi Estuary especially following pollution events.
2. The advisory against the collection of shellfish from Waihi Estuary be maintained.
3. A similar warning be implemented against the collection of shellfish from beds adjacent to Tilby Point in Tauranga Harbour.
4. Warnings issued after significant sewage spills should be kept in place until testing of shellfish for viral presence is completed and clear results received before warnings are lifted. Testing should be carried out at least 28 days after the sewage spill by the person/agency responsible for the contamination.
5. Warnings issued after significant sewage spills should be kept in place for a minimum of 3 months within 50 m of the discharge point when testing for the presence of viral contamination is not completed.
6. National guideline bacteria and virus limits should be developed for shellfish gathered for personal consumption to assist health authorities and local authorities to carry out their regulatory functions. In the interim, the microbiological limits for commercially gathered shellfish should be applied to shellfish collected non-commercially.
7. Further study be done to determine the relative contribution of different sources of pollution.
8. The agencies involved develop a communications plan to advise the public of the conclusions of this report
9. An area recommended for further research is a survey to determine the incidence of relevant illness amongst collectors and consumers of shellfish from high risk locations, and taking into account methods of preparation of shellfish, should be undertaken.
10. Any estimate of the faecal loading from avian sources would have to include not only waterfowl but also seabird population and terrestrial avian species. This is out of the scope of this survey and is highlighted as an information gap for future work.
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 57 References
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Microbiological Quality of Shellfish in Estuarine Areas Report 2009 60 Appendices
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 61
Appendix 1 – Sampling site Location Details
Water Surveillance Site Description Source Map Ref Easting Northing Sampling Frequency BOP150022 Bowentown Boat Ramp Tauranga Harbour U13:7320-1186 2773200 6411860 Monthly BOP150027 Tanners Point Jetty Tauranga Harbour U13:7087-0930 2770870 6409300 Monthly BOP150023 Kauri Point Jetty Tauranga Harbour U13:7328-0509 2773280 6405090 Monthly BOP160032 Ongare Point Tauranga Harbour U13:7280-0680 2772800 6406800 Monthly BOP150026 Pahoia Beach Rd Tauranga Harbour U14:7515-9236 2775150 6392360 Monthly BOP150014 Omokoroa, Wharf. Tauranga Harbour U14:7980-9210 2779800 6392100 Monthly BOP150013 Te Puna Beach, Pitua Rd. Tauranga Harbour U14:8230-8920 2782300 6389200 Monthly BOP150012 Otumoetai, Beach Rd. Tauranga Harbour U14:8732-8854 2787320 6388540 Monthly BOP730024 Waipu Boat Ramp Tauranga Harbour U14:9080-8770 Monthly BOP150021 Toll Bridge Marina Tauranga Harbour U14:9050-8750 2790500 6387500 Monthly BOP160024 Pilot Bay Tauranga Harbour U14:9100-9000 2791000 6390000 Monthly BOP150011 Maungatapu Bridge Tauranga Harbour U14:9140-8340 2791400 6383400 Monthly BOP150006 Little Waihi Domain Little Waihi Estuary V14:1680-7650 Monthly
Shellfish Surveillance Site Description Source Map Ref Easting Northing Pois Beach Cockles Monthly Te Puna Estuary Oysters Monthly Te Puna - Waipa Road Horse Mussel Monthly Waikareao Entrance Cockles Monthly Tilby Point Pipi Monthly Opposite Pilot Bay Pipi Monthly Waihi Estuary -Little Waihi Pipi Monthly
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 62
Appendix 2 – Water Quality Surveillance Results
*ns = not sampled Faecal Sampling Site Date Sampled E.coli Enterococci Coliforms Bowntown Boat Ramp 03-Oct-07 11 0.5 48 Tanners Point 03-Oct-07 10 1 41 Kauri Point Jetty 03-Oct-07 14 3 47 Ongare Point 09-Oct-07 0.5 0.5 0.5 Pahoia Beach Road 03-Oct-07 50 14 240 Omokoroa Beach Road 03-Oct-07 8 9 28 Te Puna Beach - Pitua Road 03-Oct-07 4 0.5 4 Otumoetai Beach 03-Oct-07 6 2 23 Waipu Boat Ramp 03-Oct-07 4 15 33 Toll Bridge Marina 03-Oct-07 16 12 41 Pilot Bay 03-Oct-07 17 18 130 Maungatapu Bridge 03-Oct-07 3 0.5 11 Little Waihi Doman 02-Oct-07 17 59 79
Bowntown Boat Ramp 30-Oct-07 2 0.5 4 Tanners Point 30-Oct-07 0.5 1 0.5 Kauri Point Jetty ns ns ns Ongare Point 30-Oct-07 210 120 290 Pahoia Beach Road 30-Oct-07 180 37 200 Omokoroa Beach Road 30-Oct-07 180 0.5 250 Te Puna Beach - Pitua Road 30-Oct-07 240 67 390 Otumoetai Beach 30-Oct-07 0.5 2 2 Waipu Boat Ramp ns ns ns Toll Bridge Marina ns ns ns Pilot Bay 30-Oct-07 0.5 6 9 Maungatapu Bridge 30-Oct-07 3 0.5 7 Little Waihi Doman 24-Oct-07 63 46 160
Bowntown Boat Ramp 07-Nov-07 8 3 8 Tanners Point 15-Nov-07 0.5 1 1 Kauri Point Jetty ns ns ns Ongare Point 14-Nov-07 0.5 1 1 Pahoia Beach Road 14-Nov-07 50 19 62 Omokoroa Beach Road 14-Nov-07 7 4 9 Te Puna Beach - Pitua Road 14-Nov-07 18 6 20 Otumoetai Beach 15-Nov-07 138 100 152 Waipu Boat Ramp ns ns ns Toll Bridge Marina ns ns ns Pilot Bay 15-Nov-07 0.5 1 2 Maungatapu Bridge 15-Nov-07 1 0.5 2 Little Waihi Doman 14-Nov-07 0.5 0.5 1
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 63
Faecal Sampling Site Date Sampled E.coli Enterococci Coliforms Bowntown Boat Ramp 13-Dec-07 0.5 1 0.5 Tanners Point 13-Dec-07 0.5 1 7 Kauri Point Jetty ns ns ns Ongare Point 12-Dec-07 7 Pahoia Beach Road 13-Dec-07 1 2 7 Omokoroa Beach Road 13-Dec-07 2 0.5 2 Te Puna Beach - Pitua Road 13-Dec-07 4 0.5 32 Otumoetai Beach 13-Dec-07 12 8 18 Waipu Boat Ramp 13-Dec-07 2 2 9 Toll Bridge Marina 13-Dec-07 1 1 1 Pilot Bay 13-Dec-07 0.5 4 0.5 Maungatapu Bridge 13-Dec-07 3 8 10 Little Waihi Doman 17-Dec-07 63 7 14
Bowntown Boat Ramp 09-Jan-08 2 3 2 Tanners Point 09-Jan-08 23 19 26 Kauri Point Jetty ns ns ns Ongare Point 09-Jan-08 136 130 159 Pahoia Beach Road 09-Jan-08 186 230 200 Omokoroa Beach Road 09-Jan-08 48 16 51 Te Puna Beach - Pitua Road 09-Jan-08 220 240 260 Otumoetai Beach 08-Jan-08 6 2 8 Waipu Boat Ramp 09-Jan-08 1 1 3 Toll Bridge Marina ns ns ns Pilot Bay 08-Jan-08 1 2 1 Maungatapu Bridge 08-Jan-08 2 0.5 5 Little Waihi Doman 08-Jan-08 17 9 22
Bowntown Boat Ramp 13-Feb-08 0.5 16 0.5 Tanners Point 13-Feb-08 0.5 1 0.5 Kauri Point Jetty 13-Feb-08 0.5 8 3 Ongare Point 11-Feb-08 2 Pahoia Beach Road 13-Feb-08 3 8 9 Omokoroa Beach Road 13-Feb-08 0.5 2 2 Te Puna Beach - Pitua Road 13-Feb-08 0.5 1 1 Otumoetai Beach 13-Feb-08 0.5 2 0.5 Waipu Boat Ramp 13-Feb-08 1 2 5 Toll Bridge Marina 13-Feb-08 1 8 12 Pilot Bay 13-Feb-08 0.5 0.5 2 Maungatapu Bridge 13-Feb-08 0.5 98 79 Little Waihi Doman 12-Feb-08 14 70 32
Bowntown Boat Ramp 19-Mar-08 0.5 6 0.5 Tanners Point 19-Mar-08 4 4 12 Kauri Point Jetty 19-Mar-08 15 3 16
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 64
Faecal Sampling Site Date Sampled E.coli Enterococci Coliforms Ongare Point 19-Mar-08 3 0.5 3 Pahoia Beach Road 19-Mar-08 1 1 1 Omokoroa Beach Road 19-Mar-08 0.5 0.5 0.5 Te Puna Beach - Pitua Road 19-Mar-08 3 0.5 17 Otumoetai Beach 19-Mar-08 0.5 0.5 0.5 Waipu Boat Ramp 19-Mar-08 0.5 0.5 5 Toll Bridge Marina 19-Mar-08 1 0.5 11 Pilot Bay 19-Mar-08 4 0.5 6 Maungatapu Bridge 19-Mar-08 3 8 12 Little Waihi Doman 19-Mar-08 38 45 48
Bowntown Boat Ramp 01-Apr-08 Tanners Point Kauri Point Jetty Ongare Point Pahoia Beach Road Omokoroa Beach Road Te Puna Beach - Pitua Road Otumoetai Beach Waipu Boat Ramp Toll Bridge Marina Pilot Bay Maungatapu Bridge Little Waihi Doman
Bowntown Boat Ramp 21-May-08 270 5 280 Tanners Point 21-May-08 1 9 2 Kauri Point Jetty 21-May-08 2 4 2 Ongare Point ns ns Pahoia Beach Road 22-May-08 1 0.5 2 Omokoroa Beach Road 22-May-08 0.5 1 0.5 Te Puna Beach - Pitua Road 21-May-08 40 14 45 Otumoetai Beach 21-May-08 20 12 20 Waipu Boat Ramp ns ns ns Toll Bridge Marina 21-May-08 2 0.5 2 Pilot Bay 22-May-08 0.5 1 1 Maungatapu Bridge 21-May-08 3 0.5 4 Little Waihi Doman 12-May-08 0.5 14 11
Bowntown Boat Ramp 01-Jun-08 0.5 0.5 0.5 Tanners Point 10-Jun-08 1 1 0.5 Kauri Point Jetty 10-Jun-08 0.5 1 5 Ongare Point 03-Jun-08 3 1 5 Pahoia Beach Road 10-Jun-08 0.5 4 5 Omokoroa Beach Road 10-Jun-08 0.5 1 0.5
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 65
Faecal Sampling Site Date Sampled E.coli Enterococci Coliforms Te Puna Beach - Pitua Road 10-Jun-08 0.5 0.5 4 Otumoetai Beach 10-Jun-08 4 2 2 Waipu Boat Ramp 10-Jun-08 1 2 4 Toll Bridge Marina 10-Jun-08 1 3 0.5 Pilot Bay 10-Jun-08 1 0.5 0.5 Maungatapu Bridge 10-Jun-08 1 0.5 2 Little Waihi Doman 24-Jun-08 30 42 160
Bowntown Boat Ramp 07-Jul-08 2 2 2 Tanners Point 07-Jul-08 4 4 9 Kauri Point Jetty 07-Jul-08 0.5 1 24 Ongare Point 31-Jul-08 97 36 140 Pahoia Beach Road 07-Jul-08 13 1 23 Omokoroa Beach Road 07-Jul-08 0.5 0.5 0.5 Te Puna Beach - Pitua Road 07-Jul-08 0.5 0.5 2 Otumoetai Beach 07-Jul-08 4 2 7 Waipu Boat Ramp ns ns ns Toll Bridge Marina 07-Jul-08 0.5 0.5 0.5 Pilot Bay 07-Jul-08 13 1 29 Maungatapu Bridge 07-Jul-08 0.5 1 1 Little Waihi Doman 07-Jul-08 4 16 6
Bowntown Boat Ramp 06-Aug-08 1 1 1 Tanners Point 06-Aug-08 0.5 2 0.5 Kauri Point Jetty 06-Aug-08 3 4 3 Ongare Point ns ns ns Pahoia Beach Road 06-Aug-08 1 1 1 Omokoroa Beach Road 06-Aug-08 1 9 1 Te Puna Beach - Pitua Road 06-Aug-08 2 1 2 Otumoetai Beach 06-Aug-08 12 0.5 12 Waipu Boat Ramp 06-Aug-08 12 1 14 Toll Bridge Marina 06-Aug-08 7 1 8 Pilot Bay 06-Aug-08 0.5 2 0.5 Maungatapu Bridge 06-Aug-08 2 1 2 Little Waihi Doman 05-Aug-08 4 4 39
Bowntown Boat Ramp 08-Sep-08 140 23 140 Tanners Point 08-Sep-08 0.5 3 0.5 Kauri Point Jetty 08-Sep-08 97 300 97 Ongare Point ns ns ns Pahoia Beach Road 08-Sep-08 4 62 4 Omokoroa Beach Road 08-Sep-08 120 110 120 Te Puna Beach - Pitua Road 08-Sep-08 120 110 120 Otumoetai Beach 08-Sep-08 300 200 300 Waipu Boat Ramp ns ns ns
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 66
Faecal Sampling Site Date Sampled E.coli Enterococci Coliforms Toll Bridge Marina 09-Sep-08 300 1000 300 Pilot Bay 08-Sep-08 21 11 21 Maungatapu Bridge 08-Sep-08 160 94 160 Little Waihi Doman 08-Sep-08 69 89 69
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 67
Appendix 3 - Shellfish Quality Surveillance Results
Shellfish Date Faecal Sampling Site E.coli Enterococci Species Sampled Coliforms Norovirus Adenovirus Temp Cond Salinity pH pH
Group I Group II degC uS/m ppt units
Pois Beach Cockles 09-Oct-07 13 80 13 Negative Negative Negative Te Puna Estuary Oysters 09-Oct-07 140 11 140 Negative Negative Negative Te Puna - Waipa Road Horse Mussel 09-Oct-07 33 9 170 Negative Negative Negative Tilby Point Pipi 09-Oct-07 8 80 8 Negative Positive Negative Opposite Pilot Bay Pipi 09-Oct-07 <2 8 <2 Negative Negative Negative Waihi Estuary -Little Waihi Pipi 09-Oct-07 300 27 300 Negative Negative Negative
Pois Beach Cockles 08-Nov-07 19 260 80 Negative Negative Negative Te Puna Estuary Oysters 08-Nov-07 130 50 240 Negative Negative Negative Te Puna - Waipa Road Horse Mussel 08-Nov-07 130 1 240 Negative Negative Negative 18.9 4428 28.7 8.27 Tilby Point Pipi 08-Nov-07 23 8 23 Negative Positive Negative 17.4 3641 27.6 8.31 Opposite Pilot Bay Pipi 08-Nov-07 4 4 23 Negative Negative Negative 15.6 3980 32.1 8.23 Little Waihi Estuary Pipi 08-Nov-07 27 17 130 Negative Negative Negative 18.3 3051 19 7.73
Pois Beach Cockles 06-Dec-07 240 500 240 Negative Negative Negative Te Puna Estuary Oysters 06-Dec-07 2400 3000 9000 Negative Negative Negative Te Puna - Waipa Road Horse Mussel 06-Dec-07 170 140 170 Negative Negative Negative 20.5 4377 31.3 8.10 Tilby Point Pipi 06-Dec-07 2 4 4 Negative Positive Negative 19.6 2693 18.7 8.21 Opposite Pilot Bay Pipi 06-Dec-07 <2 260 <2 Negative Negative Negative 18.6 4648 35 8.21 Waihi Estuary -Little Waihi Pipi 06-Dec-07 4 700 20 Negative Negative Negative 1859 14.8 8.18
Pois Beach Cockles 07-Jan-08 30 34 30 Negative Negative Negative Te Puna Estuary Oysters 07-Jan-08 130 50 170 Negative Negative Negative Te Puna - Waipa Road Horse Mussel 07-Jan-08 2 2 2 Negative Negative Negative 26.8 5360 34 8.5
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 68
Shellfish Date Faecal Sampling Site E.coli Enterococci Species Sampled Coliforms Norovirus Adenovirus Temp Cond Salinity pH pH
Group I Group II degC uS/m ppt units
Tilby Point Pipi 07-Jan-08 1 4 2 Negative Negative Negative 23.8 3550 23 8.5 Opposite Pilot Bay Pipi 07-Jan-08 1 4 2 Negative Negative Negative 21.2 4880 34.9 8.30 Waihi Estuary -Little Waihi Pipi 07-Jan-08 130 17 130 Negative Negative Negative
Pois Beach Cockles 07-Feb-08 240 7000 500 Negative Positive Negative Te Puna Estuary Oysters 07-Feb-08 5000 5000 5000 Negative Negative Negative Te Puna - Waipa Road Horse Mussel 07-Feb-08 23 23 23 Negative Positive Negative 23.7 5100 33.5 8.5 Tilby Point Pipi 07-Feb-08 23 22 50 Negative Positive Negative 21.8 4100 28.3 8.39 Opposite Pilot Bay Pipi 07-Feb-08 240 9 3000 Positive Positive Positive 21.7 4690 33.4 Waihi Estuary -Little Waihi Pipi 07-Feb-08 80 30 140 Negative Positive Positive 21.7 4090 26.2 8.19
Pois Beach Cockles 03-Mar-08 130 220 240 Negative Negative Negative Te Puna Estuary Oysters 03-Mar-08 34 140 1600 Negative Negative Negative Te Puna - Waipa Road Horse Mussel 03-Mar-08 240 140 240 Negative Negative Negative 25 5140 33.9 8.60 Tilby Point Pipi 03-Mar-08 240 27 240 Negative Positive Negative 21.5 4401 31.6 8.39 Opposite Pilot Bay Pipi 03-Mar-08 280 900 1600 Negative Positive Negative 20.9 4792 34.4 8.30 Waihi Estuary -Little Waihi Pipi 03-Mar-08 2100 260 2100 Negative Negative Negative
Pois Beach Cockles 07-Apr-08 130 2400 230 Negative Negative Negative Te Puna Estuary Oysters 07-Apr-08 270 340 1400 Negative Negative Positive Te Puna - Waipa Road Horse Mussel 07-Apr-08 80 20 80 Negative Negative Negative 20.9 4352 28.1 8.60 Tilby Point Pipi 08-Apr-08 10 20 10 Negative Negative Negative 21.3 3768 25.9 8 Opposite Pilot Bay Pipi 07-Apr-08 500 80 500 Negative Positive Negative 20.7 4738 34 7.80 Waihi Estuary -Little Waihi Pipi 08-Apr-08 80 20 80 Negative Negative Negative 19.9 3869 24.7
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 69
Shellfish Date Faecal Adenoviru Con Sampling Site E.coli Enterococci Species Sampled Coliforms Norovirus s Temp d Salinity pH pH
Group I Group II degC uS/m ppt units
Pois Beach Cockles 07-May-08 3000 1300 17000 Negative Negative Negative Te Puna Estuary Oysters 07-May-08 40 800 300 Negative Negative Negative Te Puna - Waipa Road Horse Mussel Waikareao Entrance Cockles 07-May-08 300 2400 700 Negative Negative Negative 17.1 3648 27.7 8.21 Tilby Point Pipi 07-May-08 40 300 500 Negative Positive Negative 15.9 2371 17.8 8.21 Opposite Pilot Bay Pipi 07-May-08 1 30 170 Negative Positive Negative 17.4 4358 33.5 8.14 Waihi Estuary -Little Waihi Pipi 07-May-08 300 500 300 Negative Negative Negative 16.1
Pois Beach Cockles 03-Jun-08 8 19 2700 Negative Positive Positive Te Puna Estuary Oysters 03-Jun-08 4 37 1600 Negative Negative Negative Te Puna - Waipa Road Horse Mussel Waikareao Entrance Cockles 03-Jun-08 50 50 240 Negative Positive Positive 15.4 3941 31.5 8.38 Tilby Point Pipi 03-Jun-08 34 130 300 Negative Positive Positive 14.9 3670 29.5 8.39 Opposite Pilot Bay Pipi 03-Jun-08 17 140 1400 Positive Positive Negative 15.7 4346 34.9 8.22 Waihi Estuary -Little Waihi Pipi 03-Jun-08 50 220 350 Negative Negative Negative 13.99 2533 15.51
Pois Beach Cockles 02-Jul-08 1 500 80 Negative Negative Negative Te Puna Estuary Oysters 02-Jul-08 5000 70 5000 Negative Negative Negative Te Puna - Waipa Road Horse Mussel Waikareao Entrance Cockles 02-Jul-08 2 230 80 Positive Positive Negative 12.3 3398 29 8.13 Tilby Point Pipi 02-Jul-08 40 70 40 Negative Positive Negative 11.9 2498 20.9 8.15 Opposite Pilot Bay Pipi 02-Jul-08 13 40 13 Negative Positive Negative 14.2 4111 34.1 8.06 Waihi Estuary -Little Waihi Pipi 02-Jul-08 17 300 170 Negative Negative Negative
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 70
Shellfish Date Faecal Sampling Site E.coli Enterococci Species Sampled Coliforms Norovirus Adenovirus Temp Cond Salinity pH pH
Group I Group II degC uS/m ppt units
Pois Beach Cockles 14-Aug-08 130 240 130 Negative Negative Negative Te Puna Estuary Oysters 14-Aug-08 80 90 240 Negative Negative Negative Te Puna - Waipa Road Horse Mussel Waikareao Entrance Cockles 14-Aug-08 300 1400 500 Negative Negative Negative 12 2355 19.5 8.10 Tilby Point Pipi 14-Aug-08 240 50 500 Negative Positive Negative 12.6 3498 28.19 8.09 Opposite Pilot Bay Pipi 14-Aug-08 30 90 30 Negative Negative Negative 12.5 3515 29.9 7.96 Waihi Estuary -Little Waihi Pipi 14-Aug-08 900 900 900 Negative Negative Negative 12.6 4286
Pois Beach Cockles 15-Sep-08 140 500 140 Negative Positive Negative Te Puna Estuary Oysters 15-Sep-08 70 500 170 Negative Negative Negative Te Puna - Waipa Road Horse Mussel Waikareao Entrance Cockles 15-Sep-08 130 130 240 Negative Positive Positive 16.4 3636 28.1 8.26 Tilby Point Pipi 15-Sep-08 80 50 80 Negative Negative Negative 15.1 3364 26.6 8.18 Opposite Pilot Bay Pipi 15-Sep-08 8 4 8 Negative Negative Negative 16.1 4206 33.3 8.15 Waihi Estuary -Little Waihi Pipi 15-Sep-08 300 50 300 Negative Negative Negative 16.01 5056 7.26
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 71
Appendix 4 – Sewage Overflow Adverse Pollution Event Sampling Results
FRNA phage G2 Norovirus Adenovirus Shellfish Date Faecal Event Samples Only Sampling Site E.coli Enterococci Species Sampled Coliforms Group I Group II Group I Group II Group III Group IV Animal Human Human Animal 19-Feb-08 14000 2200 14000 Positive Positive Positive Negative Positive Negative Negative 21-Feb-08 1400 1300 1400 Positive Positive Negative Negative Positive Negative Negative 25-Feb-08 9000 1700 9000 Positive Positive Positive Negative Positive Positive Negative Pipis and 04-Mar-08 330 1700 330 Negative Positive Negative Negative Negative Negative Negative cockles Anchorage Grove 17-Mar-08 23 170 900 Positive Positive Negative Negative Positive Negative Negative - 50m 08-Apr-08 Negative Positive Negative Positive Positive Negative Negative 15-May-08 9000 9000 9000 Negative Positive Negative Positive Positive Negative Negative 19-Feb-08 14000 14000 Water 20-Feb-08 Negative Positive Positive Positive Positive Negative Negative 21-Feb-08 1400 1400
Anchorage Grove 25-Feb-08 9000 - 500m 19-Feb-08 2400 3000 2400 Positive Positive Positive Negative Positive Negative Negative 21-Feb-08 1700 1700 1700 Positive Positive Negative Negative Positive Positive Negative 25-Feb-08 13000 1700 13000 Positive Positive Negative Negative Positive Negative Negative Cockles 04-Mar-08 1400 22000 700 Positive Positive Positive Negative Positive Negative Negative 17-Mar-08 27 140 1600 Positive Positive Negative Positive Positive Negative Negative 08-Apr-08 2400 1300 2400 Negative Negative Negative Negative Negative Negative Negative 15-May-08 19-Feb-08 2400 2400 Water 21-Feb-08 1700 1700 25-Feb-08 13000
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 72
Pilot Bay 19-Feb-08 11 1600 30 Negative Negative Negative Negative Negative Negative Negative 21-Feb-08 <2 220 <2 Negative Positive Negative Negative Positive Negative Negative 25-Feb-08 80 30 130 Negative Negative Negative Negative Positive Positive Negative Pipis 03-Mar-08 280 900 1600 Negative Positive Negative Negative Negative Negative Negative 17-Mar-08 <2 6 <2 Negative Positive Negative Negative Negative Negative Negative 07-Apr-08 80 20 80 Negative Positive Negative Negative Positive Negative Negative 15-May-08 19-Feb-08 11 30 Water 21-Feb-08 <2 <2 25-Feb-08 130
Tilby Pt 19-Feb-08 4 500 4 Negative Positive Negative Negative Negative Negative Negative 21-Feb-08 80 500 80 Negative Negative Negative Negative Negative Negative Negative
25-Feb-08 700 350 700 Negative Positive Negative Negative Negative Negative Negative Pipis 03-Mar-08 240 27 240 Negative Positive Negative Negative Positive Negative Negative 17-Mar-08 1 14 8 Negative Negative Negative Positive Negative Negative Negative 07-Apr-08 10 20 10 Negative Negative Negative Negative Negative Negative Negative 15-May-08 19-Feb-08 4 4 Water 21-Feb-08 80 80 25-Feb-08 700
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 73
Appendix 5 – Rainfall Adverse Pollution Event Sampling Results
Shellfish Sample F. Adeno- Sampling Site E.coli Ent Norovirus FRNA phage G2 (Event Samples Only ) Temp Cond Sal pH Species Date Col virus
Group Group Group Group Group Group pH
I II I II III IV °°°C uS/m ppt unit Animal Human Human Animal Pois Beach Cockles 17-Apr-08 1700 410 490 Negative Negative Negative Negative Negative Negative Negative Te Puna Estuary Oysters 17-Apr-08 3500 2400 5400 Negative Negative Negative Negative Negative Negative Negative Te Puna - Waipa Horse Road Mussel 17-Apr-08 3500 7900 2400 Negative Negative Negative Negative Positive Negative Negative Tilby Point Pipi 17-Apr-08 5400 1300 3500 Negative Positive Positive Positive Negative Negative Negative Opposite Pilot Bay Pipi 17-Apr-08 1700 7900 1700 Negative Negative Negative Negative Negative Negative Negative Waihi Estuary – Little Waihi Pipi 17-Apr-08 950 1300 950 Negative Negative Negative Negative Negative Negative Negative
Pois Beach Cockles 18-Apr-08 160 330 310 Negative Positive Negative Negative Positive Positive Negative Te Puna Estuary Oysters 18-Apr-08 1300 490 2400 Negative Negative Negative Positive Negative Negative Negative Te Puna - Waipa Horse Road Mussel 18-Apr-08 1300 330 1100 Negative Negative Negative Positive Negative Negative Negative Tilby Point Pipi 18-Apr-08 1300 490 1300 Negative Positive Negative Positive Negative Negative Negative 18.8 749 4.7 7.7 Opposite Pilot Bay Pipi 18-Apr-08 2400 230 700 Negative Positive Negative Negative Negative Negative Negative 18.9 4207 30.8 8 Waikareao Entrance Cockles 18-Apr-08 Negative Positive Negative Positive Positive Negative Negative Waihi Estuary – Little Waihi Pipi 18-Apr-08 16000 490 3500 Negative Negative Negative Negative Positive Negative Negative
Pois Beach Cockles 21-Apr-08 170 170 170 Negative Negative Negative Negative Negative Negative Negative Te Puna Estuary Oysters 21-Apr-08 300 2400 300 Negative Negative Negative Negative Positive Negative Negative Te Puna - Waipa Horse No Road Mussel sample Tilby Point Pipi 21-Apr-08 500 50 500 Negative Negative Negative Negative Positive Negative Negative 16.8 2920 8.1 Opposite Pilot Bay Pipi 21-Apr-08 170 4 300 Negative Negative Negative Negative Negative Negative Negative 18.3 3430 8.1 Waikareao Entrance Cockles 21-Apr-08 70 500 1600 Negative Negative Negative Positive Positive Negative Negative 17.8 3990 8.1 Waihi Estuary – Little Waihi Pipi 21-Apr-08 40 900 500 Negative Negative Negative Negative Negative Negative Negative 18.2 2390 14.61 8.1
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 74
Shellfish Date Adeno- Sampling Site E.coli Ent F. Col Norovirus FRNA phage G2 (Event Samples Only ) Temp Cond Sa.l pH Species Sampled virus Group Group Group Group Group Group pH
I II I II III IV °°°C uS/m ppt unit Animal Human Human Animal
Pois Beach Cockles 23-Apr-08 110 130 45 Negative Negative Negative Positive Positive Positive Negative Te Puna Estuary Oysters 23-Apr-08 110 78 330 Negative Negative Negative Negative Positive Negative Negative Te Puna - Waipa Horse No Road Mussel sample 16.3 2715 20.4 8 Waikareao Entrance Cockles 23-Apr-08 70 240 1300 Negative Positive Negative Negative Positive Negative Negative 17.6 3862 29.1 8.07 Tilby Point Pipi 23-Apr-08 500 68 45 Negative Negative Positive Positive Positive Negative Negative Negativ Opposite Pilot Bay Pipi 23-Apr-08 70 78 210 Negative Negative Negative Negative e Negative Negative 18.4 4607 34.8 8.06 Waihi Estuary -Little Waihi Pipi 23-Apr-08 1300 330 1300 Negative Negative Negative Negative Positive Negative Negative
Pois Beach Cockles 01-May-08 140 500 170 Negative Negative Negative Positive Positive Positive Negative Te Puna Estuary Oysters 01-May-08 240 37 140 Negative Negative Negative Positive Positive Negative Negative Te Puna - Waipa Horse No Road Mussel sample Waikareao Entrance Cockles 01-May-08 130 2800 390 Negative Positive Negative Positive Positive Negative Negative 17.2 2750 8.1 Tilby Point Pipi 01-May-08 300 500 300 Negative Negative Negative Positive Positive Negative Negative 18 3840 8.2 Opposite Pilot Bay Pipi 01-May-08 240 27 300 Negative Positive Negative Negative Positive Positive Negative 18.1 4040 8.2 Waihi Estuary -Little Waihi Pipi 01-May-08 1 3000 1600 Negative Negative Negative Positive Positive Negative Negative 16.2
Pois Beach Cockles 07-May-08 3000 1300 17000 Negative Negative Negative Positive Positive Negative Negative Te Puna Estuary Oysters 07-May-08 40 800 300 Negative Negative Negative Positive Positive Positive Negative Te Puna - Waipa Horse No Road Mussel sample Waikareao Entrance Cockles 07-May-08 300 2400 700 Negative Negative Negative Positive Positive Negative Negative 17.1 3648 27.7 8.21 Tilby Point Pipi 07-May-08 40 300 500 Negative Positive Negative Positive Positive Negative Negative 15.9 2371 17.8 8.21 Opposite Pilot Bay Pipi 07-May-08 1 30 170 Negative Positive Negative Positive Positive Negative Negative 17.4 4358 33.5 8.15 Waihi Estuary -Little
Waihi Pipi 07-May-08 300 500 300 Negative Negative Negative Positive Positive Negative Negative 16.1
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 75
Shellfish Sample Adeno- Sampling Site E.coli Ent F. Col Norovirus FRNA phage G2 (Event Samples Only ) Temp Cond Sa.l pH Species Date virus Group Group Group Group Group Group pH
I II I II III IV °°°C uS/m ppt unit Animal Human Human Animal
Pois Beach Te Puna Estuary Oysters 15-May-08 22 220 50 Negative Negative Negative Positive Negative Negative Negative Te Puna - Waipa Horse Road Mussel 15-May-08 Tilby Point Pipi 15-May-08 30 11 30 Negative Negative Negative Negative Positive Negative Negative 13.9 3610 8.2 Opposite Pilot Bay Pipi 15-May-08 17 9 26 Negative Positive Negative Negative Negative Negative Negative 14.5 3210 8.2 Waikareao Entrance Cockles 15-May-08 27 800 80 Negative Negative Negative Positive Positive Negative Negative 15.9 4190 8.2 Waihi Estuary - Little Waihi Pipi 15-May-08 170 700 300 Negative Negative Negative Negative Positive Negative Negative 13.6 2710 8.2
Pois Beach Cockles 21-May-08 2 220 3000 Negative Negative Negative Negative Positive Negative Negative Te Puna Estuary Oysters 21-May-08 12 220 170 Negative Negative Negative Negative Positive Negative Negative Te Puna - Waipa Horse Road Mussel 21-May-08 Tilby Point Pipi 21-May-08 4 22 70 Negative Negative Positive Negative Positive Negative Negative 14.2 3440 27.9 8.3 Opposite Pilot Bay Pipi 21-May-08 1 1 40 Positive Positive Positive Negative Negative Negative Negative 16 4320 34.4 8.2 Waikareao Entrance Cockles 21-May-08 40 110 700 Negative Positive Negative Negative Positive Negative Negative 14.3 3100 24.8 8.3 Waihi Estuary - Little Waihi Pipi 21-May-08 90 130 800 Negative Negative Negative Positive Positive Negative Negative 15.1 3420 21.5 10.3
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 76
Appendix 6 – Rainfall Adverse Pollution Event Data
Telemetered Rainfall Sites
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 77
Wairoa River below Ruahihi - Flow
140 120 100 80 /s 3
m 60 40 20 0 12/04/08 22/04/08 02/05/08 12/05/08 22/05/08 01/06/08
Wairoa River flow below Ruahihi
Rainfall - Goodall @ Waipapa 120
100
80
60 mm
40
20
0
8 08 /08 08 0 08 08 4 /04/ /04/ 05/ 05/ 1 5 2/05/ 9/ 1 18/0 2 16/05/08 23/ 30/05/08
Goodalls @ Waipapa Rainfall (second most northerly rainfall site)
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 78
Rainfall - Omokoroa 60
50
40
30 mm
20
10
0
08 08 08 08 /04/ /04/ 05/ /05/08 /05/ 2/05/08 9/ 11/04/08 18 25 16 23/05/08 30
Omokoroa Rainfall (at harbour)
Rainfall - Tuapiro 60
50
40
30 mm
20
10
0
8 5/0 /0 2 9/05/08 11/04/08 18/04/08 25/04/08 16/05/08 23/05/08 30/05/08
Tuapiro Rainfall (most northerly rainfall)
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 79
Rainfall - Mangorewa 100 90 80 70 60 50 mm 40 30 20 10 0
8 8 08 08 /08 /0 5 5 /08 04/ 0 0 5 8/04/0 5/04/ 2/ 9/ 11/ 1 2 16/05/08 23/05/08 30/0
Mangorewa – Pongakawa Rainfall (relates to Waihi Estuary)
Rainfall - Pongakawa 80
70
60
50
40 mm
30
20
10
0
8 8 0 08 08 0 08 04/ 04/ /05/08 05/ 05/ 1/04/08 2/05/ 9/05/08 1 18/ 25/ 16 23/ 30/
Pongakawa Rainfall (relates to Waihi Estuary)
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 80
Appendix 7 - Total Daily Rainfall Data
Tuapiro Rainfall at Woodland Road
120
100
80
60 mm
40
20
0 5/10/07 2/11/07 8/02/08 7/03/08 4/04/08 2/05/08 8/08/08 5/09/08 21/09/07 19/10/07 16/11/07 30/11/07 14/12/07 28/12/07 11/01/08 25/01/08 22/02/08 21/03/08 18/04/08 16/05/08 30/05/08 13/06/08 27/06/08 11/07/08 25/07/08 22/08/08 19/09/08
Waipapa Rainfall at Goodalls Road
140
120
100
80
mm 60
40
20
0 5/10/07 2/11/07 8/02/08 7/03/08 4/04/08 2/05/08 8/08/08 5/09/08 19/10/07 16/11/07 30/11/07 14/12/07 28/12/07 11/01/08 25/01/08 22/02/08 21/03/08 18/04/08 16/05/08 30/05/08 13/06/08 27/06/08 11/07/08 25/07/08 22/08/08 19/09/08 21/09/07
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 81
Omokoroa Rainfall at Omokoroa 60
50
40
30 mm 20
10
0 5/10/07 2/11/07 8/02/08 7/03/08 4/04/08 2/05/08 8/08/08 5/09/08 21/09/07 19/10/07 16/11/07 30/11/07 14/12/07 28/12/07 11/01/08 25/01/08 22/02/08 21/03/08 18/04/08 16/05/08 30/05/08 13/06/08 27/06/08 11/07/08 25/07/08 22/08/08 19/09/08
Waimapu Rainfall at McCarolls Farm
90 80 70 60 50
mm 40 30 20 10 0 5/10/07 2/11/07 8/02/08 7/03/08 4/04/08 2/05/08 8/08/08 5/09/08 21/09/07 19/10/07 16/11/07 30/11/07 14/12/07 28/12/07 11/01/08 25/01/08 22/02/08 21/03/08 18/04/08 16/05/08 30/05/08 13/06/08 27/06/08 11/07/08 25/07/08 22/08/08 19/09/08
Mangorewa Rainfall at Saunders Farm 120
100
80
60 mm
40
20
0 5/10/07 2/11/07 8/02/08 7/03/08 4/04/08 2/05/08 8/08/08 5/09/08 21/09/07 19/10/07 16/11/07 30/11/07 14/12/07 28/12/07 11/01/08 25/01/08 22/02/08 21/03/08 18/04/08 16/05/08 30/05/08 13/06/08 27/06/08 11/07/08 25/07/08 22/08/08 19/09/08
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 82
Pongakawa Rainfall at Pongakawa 100 90 80 70 60 50 mm 40 30 20 10 0 5/10/07 2/11/07 8/02/08 7/03/08 4/04/08 2/05/08 8/08/08 5/09/08 21/09/07 19/10/07 16/11/07 30/11/07 14/12/07 28/12/07 11/01/08 25/01/08 22/02/08 21/03/08 18/04/08 16/05/08 30/05/08 13/06/08 27/06/08 11/07/08 25/07/08 22/08/08 19/09/08
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 83
Appendix 8 - Average Daily River Flow Data
Wairoa River Flow below Ruahihi Power Station 140
120
100
80 /s 3
m 60
40
20
0 21/09/07 05/10/07 19/10/07 02/11/07 16/11/07 30/11/07 14/12/07 28/12/07 11/01/08 25/01/08 08/02/08 22/02/08 07/03/08 21/03/08 04/04/08 18/04/08 02/05/08 16/05/08 30/05/08 13/06/08 27/06/08 11/07/08 25/07/08 08/08/08 22/08/08 05/09/08 19/09/08
Kopurereruru River Flow at SH29 Bridge 14
12
10
8 /s 3
m 6
4
2
0 21/09/07 05/10/07 19/10/07 02/11/07 16/11/07 30/11/07 14/12/07 28/12/07 11/01/08 25/01/08 08/02/08 22/02/08 07/03/08 21/03/08 04/04/08 18/04/08 02/05/08 16/05/08 30/05/08 13/06/08 27/06/08 11/07/08 25/07/08 08/08/08 22/08/08 05/09/08 19/09/08
Wamapu River at McCarols Farm 25
20
15 /s 3 m 10
5
0 21/09/07 05/10/07 19/10/07 02/11/07 16/11/07 30/11/07 14/12/07 28/12/07 11/01/08 25/01/08 08/02/08 22/02/08 07/03/08 21/03/08 04/04/08 18/04/08 02/05/08 16/05/08 30/05/08 13/06/08 27/06/08 11/07/08 25/07/08 08/08/08 22/08/08 05/09/08 19/09/08
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 84
Pongakawa Stream at Old Coach Road 8 7 6 5 /s
3 4 m 3 2 1 0 21/09/07 05/10/07 19/10/07 02/11/07 16/11/07 30/11/07 14/12/07 28/12/07 11/01/08 25/01/08 08/02/08 22/02/08 07/03/08 21/03/08 04/04/08 18/04/08 02/05/08 16/05/08 30/05/08 13/06/08 27/06/08 11/07/08 25/07/08 08/08/08 22/08/08 05/09/08 19/09/08
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 85
Appendix 9 – Sewage Reticulated and Non-Reticulated Areas
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 86
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 87
Appendix 10 – Reticulated Sewage Overflow Data
Discharge meets Overflow Address Cause of Blockage General comment criteria for event to water sampling MH discharging into GP at head of cul de sac. No solids or paper. Clear with jetter and 2 x sucker trucks, one intercepting discharge into estuary, the other Sixth Avenue Fat Y No working with jetter, flushing SW moving and sucking CP's. Clean and disinfect. Erect health warning signs. Sewer was overflowing when I arrived at site. There was minimal flow running down kerb and channel to cesspit. Grass growing over lid of MH had contained Fraser Street Grass Y No more if not all of the solid waste. Son once we had cleaned blockage, sucker truck could clean up material in grass Sucker truck to drop levels until fat blockage cleared by jetting truck. Discharge into SW via cesspit. Sandbag SW outlet and suck out from Man Hole halfway. Palm Springs Blvd Fat Y No No sewer smells at outlet into ponds. Flush SW mains and suck. Erect warning signs along pond Yes. Major overflow. Shellfish Rising main - Small amount of sewage between valve and sea wall. Dig down to Anchorage Grove Unknown Y project event rising main. No leak evident. Tides in over sea wall. Make safe until Monday sampling instigated. 3rd party damage Glenlyon Ave Y Thrusted stormwater pipe by private company No thrusting of rising main Maleme Street unknown Y Blockage in connection to receiving manhole to Maleme pump station No unknown until pump Blockage at pump station and cracked connection pipe. Suspect vandalism at 2nd Ave east Y No station works finished works site Lagoon Place unknown Y Blockage in line between two manholes No Overloaded sewer pipe Third Avenue Y Intense rain fall event caused sewer system to become overloaded. No system Cypress Street Fat build up Y Overflow from MH reported to be fat build up No Courtney Road not recorded Y Blockage recorded closer to MH10066 No Jetted to clear line. Flow mostly s/w because of heavy rain draining to open Awaiti Place Fat? Heavy rain event Y No drain close to MH Ohauiti road heavy Rain Y Man hole surcharged in heavy rain. Reported by owner No Esmeralda Street Plastic bags, ball and toys Y Overflowed into cesspit, required signage No
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 88
Discharge meets Overflow Address Cause of Blockage General comment criteria for event to water sampling Third party Piles from Minor overflow. Habitat for Humanity building retaining wall damaged pipe in Mansels Road retaining wall being Y No several locations. Pipe line need to be re-laid. constructed Cambridge Road Not known Y unknown No Pump Station Shutdown Chadwick Road caused the overflow from Y Error from City Care while managing scheduled pump shut down. No a number of MH's. Third party: WWTP shut City Care operations caused overflow during a scheduled shut down at Chadwick Road Y No down fault Chapel Street WWTP Overflow was from MHid2860 however blockage was between Mhids 2861 Maleme Street Fat Y & 12753. Cleared blockage with jetter, large quantity of fat identified as No cause. Sewer was overflowing when City Care arrived at site. There was Large quantity of Fat in Glenlyon Ave Y considerable flow from upstream MH2860 draining directly in the the No pipeline adjoining drain.
Microbiological Quality of Shellfish in Estuarine Areas Report 2009 89