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Marine Biotoxin Monitoring and Response Manual for Non-Commercial Shellfish
5 PROCEDURES
5.1 General
The key components of the non-commercial marine biotoxin monitoring system are as follows:
Weekly phytoplankton sampling at suitable sites to provide early warning of shellfish toxicity.
Weekly shellfish flesh testing for PSP toxins at sites with significant previous history of Alexandrium catenella and Gymnodinium catenatum induced PSP contamination.
Surveillance and investigation of TSP cases.
5.1.2 Monitoring for Paralytic Shellfish Poison (PSP)
PSP is monitored for using combined flesh sampling and phytoplankton sampling in North Island areas where there has been recurrent significant (up to 30mg/kg) PSP toxicity, principally from Alexandrium catenella and Gymnodinium catenatum. In the South Island, these species have not been found to cause shellfish toxicity, although there has been one incident where Alexandrium minutum caused PSP toxicity exceeding the warning level.
5.1.3 Monitoring for Domoic Acid
Domoic Acid is not monitored for directly by testing shellfish, instead water samples are taken and are checked for Pseudonitzchia species phytoplankton. Some of these are highly toxic, others less so, and some are non-toxic. (Refer Appendix 1 for trigger levels for individual species). Because the individual species are difficult if not impossible to differentiate under a light microscope, a genetic probe may be done to determine the species present. More detail on this is found under the section “Actioning Phytoplankton Results”.
5.1.4 Monitoring for Diarrhetic Shellfish Poison (DSP)
DSP is monitored for using phytoplankton samples. When the trigger levels in Appendix 1 are breached, flesh samples should be taken and analysed for DSP as soon as possible. Generally mussels are the preferred species for sampling for DSP.
It is essential that Sampling Providers carry out sampling in a safe manner. The rule “if in doubt, don’t go out” must be applied.
The local marine biotoxin management or sampling plan must address safety issues associated with each marine biotoxin sample site, and specify safety procedures, equipment and competency requirements for sampling personnel, including compliance with the relevant statutory requirements of the Department of Labour (Occupational Safety and Health) and of the Maritime Safety Authority.
Procedures should also address safety measures for sampling during an RIS Event.
Sampling officers are the people who physically take the shellfish or water samples for the non-commercial monitoring programme.
DHBs should ensure that sub-contractors are provided with suitable identification so fisheries staff can identify them as people authorised to take shellfish samples by a Food Act or Animal Products Act Officer. The Fisheries Act 1996 sections 89 (2) (g) and 89 (2) (ha) permit such duly authorised people to collect in excess of the normal recreational limits as samples.
Sampling Providers act under the direction of the NZFSA Senior Programme Manager Animal Products who is an officer appointed under the Animal Products Act.
Sampling officers must be trained in shellfish and phytoplankton sampling and monitoring activities by an HPO, RSS or Sampling Provider. The amount and type of training will depend on where and how samples are to be taken, and must be documented in the local management or sampling plan.
Sampling officers should have their field activities reviewed no less frequently than annually by an HPO or Sampling Provider. This could involve accompanying them while on a sampling run and checking with the laboratory as to the condition of samples received and completeness of documentation. The laboratory is required to notify DHBs and Sampling Providers of insufficient or out of specification samples when they are received so the DHB can take corrective action.
DHBs and Sampling Providers must record training and review details (what, by whom and when) for all sampling officers and make such records available to the NZFSA, on request.
5.2 Phytoplankton Monitoring
5.2.1 Selection of Phytoplankton Monitoring Sites
Selection of routine monitoring sites is primarily the responsibility of the NZFSA, in consultation with the phytoplankton laboratory, DHBs and Sampling Providers. These sites are specified in the sampling contracts NZFSA has with providers of services.
The following factors are considered when selecting phytoplankton monitoring sites. Sites should be:
• Representative of common water bodies and located at points where blooms are likely to persist.
• Accessible in most weather conditions.
• Relatively free of land runoff.
• Clear of the surf zone wherever possible.
• Be sited to protect significant shellfish gathering areas. (This does not mean that they need to be sited right in those areas as there may be locations that better represent what is happening more widely in an area while still representing the gathering area.)
5.2.2 Collection of Phytoplankton Samples
Most phytoplankton samples taken in the non-commercial programme are taken by a grab or hose sampling method which provides an integrated sample for analysis.
An option may be to take discrete depth samples using a Van Dorn sampler. (Refer Appendix 2) Routinely a portion of each sample bottle is composited for analysis. In an Event situation, individual samples may be analysed to provide depth profiles which may provide useful information for management. Where a person managing an Event requires depth profile information, they may request depth profile analysis directly from the phytoplankton laboratory after obtaining permission from NZFSA.
5.2.3 Handling and Dispatch of Phytoplankton Samples
The NZFSA contracts the phytoplankton laboratory to carry out analysis of shellfish growing water samples for phytoplankton species.
In collecting phytoplankton samples, the sampling officer must follow procedures set out in Appendix 2. When submitting a phytoplankton sample for analysis, the sampling officer must fill out the relevant section of the Cawthron Institute sample form (Appendix 5) and submit this along with the sample.
Each sample bottle must be labelled with the sampling date, name and phytoplankton site code and location of the sampling site, and the depth (if taken by random sampler) at which the sample was taken. Use labels that will not become detached and write on them with permanent markers.
Samples must reach the phytoplankton laboratory as soon as possible after collection, ideally within 24 hours and definitely within 48 hours of collection. Phytoplankton samples should not be iced or have chilly pads with them for transit because this may kill cells in live samples.
5.2.4 Notification of Phytoplankton Results
The NZFSA contracts the phytoplankton laboratory to notify DHBs and Sampling Providers by phone and fax when toxic phytoplankton numbers reach or exceed trigger levels for flesh sampling (see Appendix 1). The phytoplankton laboratory may also issue interim results when they identify suspected toxic species. However, DHBs and Sampling Providers should not initiate extra flesh sampling until toxic species are positively identified as being at or above trigger levels and with the agreement of NZFSA.
5.3 Shellfish Monitoring
5.3.1 Selection of Shellfish Sampling Sites
Selection of routine shellfish sampling sites is primarily the responsibility of the NZFSA, in consultation with DHBs and Sampling Providers.
Routine shellfish sampling sites in the non-commercial monitoring programme are specified in contracts with DHBs and with other Sampling Providers. Sites may be varied when Event sampling is underway. They may also be varied, in consultation with the NZFSA, for routine sampling purposes.
In selecting or relocating marine biotoxin shellfish sampling sites, the following factors are considered:
• the history of marine biotoxin and phytoplankton activity in each area
• coverage of major shellfish harvesting areas
• common water bodies
• shellfish species available
• amount of harvesting by non-commercial harvesters
• open seasons for seasonal fisheries
• areas closed because of rahui, Ministry of Fisheries directives, marine reserves and signposted sewage/faecally contaminated areas
• accessibility in all weather conditions
• major current flows
• retention zones and circular flow patterns
• areas where rivers have a major impact on salinity
• any other factors considered relevant.
DHBs and Sampling Providers should also consult with other relevant organisations and groups to obtain a complete picture of the shellfish fisheries in the area (e.g. NZFSAVA, Ministry of Fisheries, the shellfish industry, Maori representatives, coastal communities, boat operators etc.).
Research agencies may also be consulted for information on phytoplankton distribution, and on oceanographic, hydrographic and meteorological processes likely to have a bearing on the definition of common water areas.
Routine monitoring sites are, and will always need to be, subject to change to meet the needs of the monitoring programme.
5.3.2 Shellfish Species – General
For monitoring purposes, bivalve species are taken because they are much more susceptable to contamination than non-bivalve species due to their filter feeding.
Mussels are the preferred species for use for monitoring for PSP and DSP. They are used as a sentinel species in both New Zealand and overseas monitoring programmes. This is because they accumulate toxins quickly and depurate them quickly.
However, some other shellfish species may retain toxin much longer than mussels such as tuatua which retain PSP for long periods, and scallops which retain ASP.
DHBs and Sampling Providers must be aware that there are differences in biotoxin accumulation, retention and depuration between different shellfish species. Hence a number of species in a toxin-affected area may need to be tested and found safe before the DHB can lift public health warnings.
PSP is generally accumulated and depurated quickly from shellfish and its presence correlates well with the causative phytoplankton species. An exception to this is tuatua which although quick to accumulate the toxin, may retain it long after the phytoplankton responsible has disappeared from the water. Tuatua have been found to retain the toxin in the siphon which may account for this. In practice this means that tuatua need to be sampled and analysed to ensure they are below warning levels if present in an area a public warning has been issued for before a warning is lifted.
Scallops do not always correlate well with other species regarding toxicity levels, especially in the case of domoic acid which is produced by Pseudonitzchia spp. This toxin, which causes ASP, appears to persist longer in scallops than in other species. This may be because the adductor muscle and roe is sampled, and the toxin detected will have migrated into the tissue from the gut and hence take longer to detoxify. (Most consumers eat only the muscle and roe from scallops, so normally, only the muscle and roe portions of non-commercial scallops are analysed.)
Because the gut and skirt of scallops can contain high levels of toxin at any time of the year consumers should be advised that these parts of the scallop should never be consumed.
A more detailed discussion on scallops can be found in the 2003 review document.
Because scallop samples are expensive to collect they will not be part of the routine monitoring programme. Instead in areas where scallops are present in significant quantities, genetic probes will be used to determine the species of Pseudonitzchia present over the period the scallop season is open. (Refer to Management of Marine Biotoxin Events below).
Paua sampling (viscera only analysed) sites are not used in the routine monitoring programme, nor is sea urchin (kina) sampling carried out. Routine monitoring of bivalve shellfish normally covers these species. However, paua gut and kina are included, as a precaution, in the list of shellfish species that should not be consumed when public health warnings are issued.
Crabs and crayfish are not routinely sampled. These species may become contaminated when shellfish in their feeding areas take in high levels of toxin. Because such contamination is mostly confined to the gut, DHBs should advise consumers, as part of their public health warning, to gut crabs and crayfish before cooking.
5.3.6 Selecting Shellfish Flesh Analyses and Sample Sizes
There are a number of options for analysis of shellfish flesh samples. It is essential that the appropriate analyses be indicated on the form submitted with the sample. See the table below:
Table 2: Sample Sizes
Toxin |
Test Methods |
Flesh Sample Size |
All (PSP, NSP, DSP, ASP) |
PSP bioassay Domoic Acid HPLC DSP ELISA NSP (ether extraction) and bioassay |
400 g flesh |
NSP only |
NSP (ether extraction) and bioassay |
150 g flesh |
Domoic Acid only |
HPLC |
12 shellfish |
DSP only |
DSP ELISA |
12 shellfish |
PSP only |
PSP bioassay |
150 g flesh |
PSP & ASP |
PSP bioassay, ASP HPLC |
150 g flesh |
PSP & ASP/DSP |
PSP bioassay, ASP HPLC, DSP ELISA |
150 g flesh |
Note: A minimum of 12 shellfish is required to obtain a sufficiently representative, pooled sample. When requesting shellfish flesh analyses outside the routine sampling programme, please take careful note of the toxins produced by particular phytoplankton species (see Management of Marine Biotoxin Events) and make sure that flesh samples are clearly marked for analysis of that toxin only. If samples are marked for analysis of the wrong toxin, or for analysis of all toxins when only one is necessary, the public may be unnecessarily exposed to risk and/or the cost of the incorrect analysis may be recovered from the sampler.
5.3.7 Dispatch and Handling of Shellfish Samples
The NZFSA contracts an approved marine biotoxin laboratory to analyse non-commercial shellfish samples for marine biotoxins. This laboratory is currently Agriquality’s AquaBiotoxTM laboratory.
Shellfish samples must arrive at the testing laboratory alive and in good condition, ideally within 24 hours and definitely within 48 hours of collection. The samples must be packed in chilly bins with ice packs and reach the laboratory at a temperature between 0 and 10 degrees Celsius.
Samples must not be frozen.
Sampling officers should collect routine samples of shellfish, wherever possible, to ensure that they arrive in the biotoxin laboratory on a Monday, Tuesday or Wednesday. Reactive samples may arrive on any weekday. Please contact the laboratory to make arrangements for receipt if samples are likely to arrive outside of normal working hours.
A properly filled out AgriQuality sample submission form must accompany all shellfish flesh samples. See Appendix 6 for a copy of the shellfish sample submission form. Labels showing site name, site code and shellfish species must be attached to each shellfish sample bag.
NZFSA contracts the approved analytical laboratory to notify DHBs and Sampling Providers by phone and fax when public warning limits are exceeded or when toxin levels are rising in areas not previously toxic.
Interim sample results for NSP and PSP that clearly exceed the regulatory limit but where samples require dilution to produce a final result must be notified as soon as the laboratory can confirm that the result will definitely exceed the public warning level. This allows appropriate action to be taken without delay.
5.4 Management of Marine Biotoxin Events
Once Phytoplankton trigger levels are exceeded or flesh samples show signs of toxicity we have an Event. Some Events come to nothing when flesh samples are taken; others result in detection of harmful levels of toxicity in shellfish. Public warnings should only be issued when toxin is detected in shellfish above the public warning levels specified in section 4.2.
5.4.2 Actioning Phytoplankton Results
Phytoplankton monitoring provides an early warning indicator of toxicity in shellfish. See Appendix 1 for the Phytoplankton Action Level Table. The detection level of toxic phytoplankton in water samples is 100 cells per litre.
In areas where phytoplankton is used as the only routine monitoring option, cell numbers at or above a trigger level should prompt immediate shellfish flesh sampling and analysis for the specific toxin produced by that phytoplankton species.
Genetic probes are required to distinguish the different proportions of Pseudonitzchia species present in water samples. Because these are more expensive to do than testing flesh samples, when Pseudonitzchia species are detected above 100,000 cells/l in plankton samples in areas where flesh samples are routinely taken (for example where routine PSP testing of flesh is undertaken) generally it is better to test a flesh sample if one is already to hand than to undertake a genetic probe. However if scallops are present in an area and the scallop season is open or if a special sampling trip is required to obtain a flesh sample, a genetic probe should be done preferentially. It should be noted that high domoic acid levels have only ever been found in mussels and scallops in New Zealand and it would therefore appear that analysing other species for it may not be worthwhile. However, more data is needed to confirm this, particularly for tuatua.
The table and diagram below provide guidance on whether to do a genetic probe or take flesh samples.
Actions to be taken when >100,000 cells/l Psuedo-nitzchia species present:
Situation |
Scallop Season Status |
Action |
No flesh samples taken routinely, no scallops in area |
N/A |
Do genetic probe before taking any shellfish samples |
Flesh sample routinely taken and available for analysis, no scallops in area |
N/A |
Analyse flesh sample for Domoic acid, no genetic probe required |
Scallops in area, no flesh sample taken routinely |
Open |
Do genetic probe before taking any shellfish samples |
Scallops in area, non-scallop flesh sample routinely taken and available for analysis |
Open |
Do genetic probe before analysing flesh sample already taken or taking scallop samples |
Scallops in area, no flesh sample taken routinely |
Closed |
Do genetic probe before taking any shellfish samples |
Scallops in area, non-scallop flesh sample routinely taken and available for analysis |
Closed |
Analyse flesh sample for Domoic acid, no genetic probe required. |
Often there will be more than one toxic Pseudonitzchia species present. The table in appendix 1 divides the Pseudonitzchia species into two groups: those that are more toxic and those that are less toxic. The more toxic species should have their cell counts aggregated and if these exceed 100,000 cells/litre then flesh testing should be initiated. The less toxic species should also have their cell counts aggregated and if these exceed 500,000 cells/litre then flesh testing should be initiated. Unless either trigger level is breached, there is no need to initiate flesh testing. (i.e.: there is no need to try and aggregate species of lower toxicity with species of higher toxicity.)
DHBs and Sampling Providers must consult the NZFSA before they undertake any non-routine sampling of phytoplankton or shellfish for non-commercial programme purposes.
Reasons for such non-routine sampling may include the following:
• to monitor the development or status of an Event
• to obtain more information about areas where toxins or toxigenic phytoplankton levels are rising towards or have exceeded a regulatory limit
• to define toxin-affected areas and species
• to ensure that previously toxin-affected areas are safe e.g. it may be necessary to take additional samples from other representative sites or shellfish species in previously toxin-affected areas before the whole area can be declared safe for public use.
Shellfish sampling undertaken in relation to an Event needs to be the minimum necessary to manage the Event. When Events are underway, routine weekly phytoplankton sampling should continue. This may be sufficient for tracking an Event, however, recognising the distances between sample points, additional phytoplankton sampling may be required. When significant toxicity is detected in shellfish from areas where phytoplankton samples are not routinely taken, water samples should be arranged (if possible), in conjunction with the phytoplankton laboratory, to ascertain the species responsible for toxin production.
Once it is clear which phytoplankton species is responsible for an Event, phytoplankton samples taken during Events (other than the routine monitoring samples) need to be marked for analysis only for the plankton species of concern.
Once shellfish samples have exceeded the public warning limits and an area has had a public warning issued, shellfish sampling within the affected area (Other than any samples routinely contracted for) should cease and water samples should be obtained and be used to track the area affected and progress of an Event. This is because water samples are easier to collect and simple to analyse, especially for a single plankton species. The focus should shift to the areas adjacent to the area subject to warning to ensure that any spread of the problem is detected. This may be done by taking water or shellfish samples as appropriate.
When the plankton results show that levels of the causative species of plankton have decreased below trigger levels, clearance flesh samples should be obtained from the affected area (see below).
Criteria for Issue of Public Warnings
DHBs must take prompt and effective public health action to discourage members of the public from gathering or consuming contaminated shellfish. The DHB should issue a public warning in the following circumstances:
Toxin levels in shellfish exceed public warning levels. (Refer section 4.2.)
Two or more cases of human illness have resulted from consumption of shellfish from an area, and symptoms are consistent with the clinical case definitions for PSP, NSP, ASP, or DSP. DHBs should use this criterion with caution and, if possible, obtain laboratory confirmation of shellfish toxicity before issuing a warning. However, they should take immediate action if, for example, the cases exhibit classic PSP symptoms within an hour of consuming shellfish.
DHBs are responsible for defining areas subject to public health warnings. It is thus essential that non-DHB Sampling Providers maintain timely and effective communication with their local DHB to enable the DHB to make well-informed decisions and be able to take prompt action to protect public health. Before making such decisions, the DHB should consult the NZFSA, and where commercial growing areas are involved, other relevant agencies including NZFSAVA Regional Shellfish Specialists and shellfish delivery centre representatives.
Generally, areas subject to warnings will extend to the next sample site below public warning limits unless there are geographic, hydrographic or historical reasons for closing smaller or larger areas.
When defining an affected area, DHBs must also take the following matters into account:
• phytoplankton information
• hydrography
• biotoxin results from adjacent areas
• any other relevant information.
When shellfish toxin levels are rising and approach the public health warning level, DHBs should immediately supply this information to industry representatives in the affected area.
During an Event, DHBs are responsible for issuing media statements to advise the public of areas shellfish should not be harvested from. They should use all media outlets with coverage in the locally affected area.
Appendix 3 contains suggested wording for such statements.
Once an Event is over and the area is free of toxicity, DHBs should issue media statements advising the public that the area is safe for shellfish gathering.
DHBs are responsible for ensuring that warning signs are posted in unsafe shellfish collecting areas and at access points (such as boat ramps). It is recommended that these signs clearly define the affected area and advise the public against consuming shellfish from within the area, and, where appropriate, be printed in languages other than English e.g. Maori, relevant Pacific and Asian languages.
DHB staff should pay regular (weekly or fortnightly) visits to all major non-commercial harvesting sites within an area subject to a public warning area, to ensure that signage is intact and to warn any people taking shellfish of the potential health consequences.
In contaminated areas where a substantial take of shellfish continues despite media publicity and other warnings, DHB staff should develop and use other strategies to encourage the public to heed public warnings.
Once areas are re-opened for shellfish gathering, the DHB should remove warning signs.
5.4.7 Communications with Local Maori and other Non-commercial User Groups
DHBs should develop effective communication strategies to ensure that local Maori and other user groups are aware when public warnings are issued about the safety of shellfish in local gathering areas. This will include contact with Iwi and community leaders to enlist co-operation and seek advice on the most appropriate ways of promoting the warning.
DHBs should develop and maintain networks and co-operative working relations with Iwi and provide technical expertise to support the Iwi’s role in community education and encouraging respect for public health warnings.
5.4.8 Notification to Regulatory Agencies and Industry
When DHBS issue public warnings, they should notify the following agencies:
• The NZFSA
• All other DHB Public Health Units and Sampling Providers
• NZFSAVA Regional Shellfish Specialists and relevant Verification Agency staff. (Where commercial areas are affected only.)
When the toxin-affected area includes commercial sites, DHB staff should immediately send formal written notification of closures and subsequent re-openings to the appropriate delivery Centre Personnel. Product recall actions may also be required.
5.4.9 Notification of Medical Practioners
When toxin levels approach those likely to result in illness, DHBs may write to medical practitioners in the affected area to advise them of the situation to let them know what sort of symptoms may be expected and to remind them of the need to notify the Medical Officer of Health of any cases. An example of such a letter is found at Appendix 4.
5.4.10 Shellfish Clearance Sampling
Before DHBs can issue a media statement advising the public that areas are safe for shellfish gathering, they should determine that the following requirements have been adequately addressed.
Two consecutive samples of shellfish should be taken at least 48 hours apart from the routinely sampled sites and species in the closed area. In areas where routine samples are not taken, sampling should be as agreed with NZFSA in advance. Samples must be must be below public health warning limits for the toxin of concern before a public warning is lifted. It may be necessary to check other species in an area are also clear of toxin – a single sample of each species should be sufficient for this purpose and these should be taken at the same time as the second clearance sample from any routinely sampled sites.
Toxin levels should be decreasing or static in consecutive clearance samples. (Note: there may be some variation between patches of shellfish in an area, especially with species such as tuatua which retain PSP toxins in low levels for long periods. Some variation is to be expected and may not be indicative of new activity.)
No cases of human illness, notified to the Medical Officer of Health and consistent with the accepted case definitions for PSP, NSP, ASP or DSP shall have resulted from the consumption of shellfish gathered since the date of collection of the first clearance sample from within or adjacent to the closed area.
DHBs should ensure that species of shellfish sampled from an area for clearance purposes are representative of those species normally gathered from the area.
Shellfish and/or phytoplankton results from adjacent areas should also be evaluated for their potential impact on the area to be opened. Toxin/toxic algae levels should also be decreasing or static in adjacent areas. DHB staff may have to contact their colleagues in adjacent DHBs to obtain this information and assess its impact on their own area.
The cell counts of toxigenic phytoplankton listed in Appendix 1 must be below trigger levels and decreasing or static.
DHBs should also consider other relevant, available information such as the hydrography of the area, and the pattern of toxicity at sample sites, to assess the potential for a recurrence of toxicity. They may also impose other conditions or limitations if these are considered necessary.
In summary, the DHB must have sufficient information to make an informed and reasoned food safety decision.
5.4.11 Reversion to Routine Sampling After High Cell Counts
Once the cell number of a toxic phytoplankton species is below the trigger level then extra shellfish sampling should cease. However, in the case of a Pseudonitzschia species bloom, shellfish sampling for ASP analysis may be continued for two weeks after cell numbers drop below the trigger level. Pseudonitzschia species often produce more toxin when the bloom “crashes” and shellfish may become more toxic as cell numbers decline.
5.5 TSP Case Investigation
Surveillance of TSP is an integral part of the non-commercial marine biotoxin monitoring programme. Health protection staff must investigate notified cases or suspected cases and record all details on the notifiable disease database (EpiSurv). The MoH’s Manual for Public Health Surveillance in New Zealand contains case definitions, the case report form and instructions for completing this form.
All cases and suspected cases of toxic shellfish poisoning are legally notifiable to Medical Officers of Health pursuant to Section 74 of the Health Act 1956. Medical practitioners must notify any such cases promptly, so that public health staff can investigate without delay. This is especially important when shellfish in the area are already toxic and there is a high likelihood of illness occurring.
Public health staff should investigate every suspected case. It is essential that all relevant sections of the standard case report form are completed, including precise details about when and where the shellfish were harvested.
If samples of the shellfish actually consumed by the ill person are not available for testing it is very important to obtain samples of the same species of shellfish from the same site as close as possible to the time of consumption by the ill person. If necessary, the investigating officer must contact other DHBs to ascertain marine farm numbers and to arrange sampling from the commercial source.
The investigating officer should assess information on the case report form against the clinical case definitions as given in the Manual for Public Health Surveillance in New Zealand. If officers require expert advice on assigning case status, they should consult epidemiologists at ESR Kenepuru Science Centre.
All data collected from suspected cases should be entered into EpiSurv, with sample results details added as they become available.
If faecal specimens provided by suspected cases are found to be positive for food or water borne pathogens, all the case data, plus these results, should be transferred to the food and waterborne disease section of EpiSurv.
Officers investigating suspected cases must take any available, relevant food samples. Such samples may include the remains of meals, samples of commercial product from the same batch(es) as those eaten by the suspected case, and samples taken from the areas where the suspect shellfish were harvested. Samples must be large enough (at least 500 g flesh weight) to allow for both marine biotoxin analysis and analysis for other pathogens and toxins (bacterial, viral etc).
When suspected cases experience gastrointestinal symptoms, they should be asked to provide faecal specimens, so that bacterial and/or viral causes of illness can be investigated and possibly eliminated.
Investigating officers must submit TSP case-related food samples, including those that are sent for marine biotoxin analysis, with a standard food laboratory sample form. Samples requiring both marine biotoxin and microbiological analysis must be handled aseptically and split into two portions, with one portion going to the public health laboratory and the other to the marine biotoxin laboratory. The associated EpiSurv case number must be written on all forms accompanying these samples, to ensure they are clearly identified as case samples.
APPENDIX 1: Non – Commercial Phytoplankton action level table
These action levels apply only to non-commercial situations and relate to composite samples. Please note that this action level table has some minor differences to the commercial phytoplankton action level table and should not be applied to commercial growing area situations.
Phytoplankton Species |
Toxin |
Level in composite sample to trigger flesh testing (Cells per Litre of seawater)1 |
Alexandrium minutum |
PSP |
400 |
Alexandrium ostenfeldii |
PSP |
400 |
Alexandrium catenella |
PSP |
100 |
Alexandrium tamarense |
PSP |
100 |
Gymnodinium catenatum |
PSP |
100 |
2Pseudo-nitzschia australis 2Pseudo-nitzschia pungens 2Pseudo-nitzschia multiseries |
ASP |
100,000 (Combined count of these 3 species) |
2Pseudo-nitzschia turgidula 2Pseudo-nitzschia fraudulenta 2Pseudo-nitzschia delicatissima 2Pseudo-nitzschia pseudodelicatissima |
ASP |
500 000 (Combined count of these 5 species) |
2Pseudo-nitzschia multistriata |
ASP |
|
3Karenia brevis |
NSP |
1,000 |
4Karenia/Karlodinium/Gymnodinium Group |
NSP |
250,000 |
Dinophysis acuta |
DSP |
500 |
Dinophysis acuminata |
DSP |
1 000 |
Prorocentrum lima |
DSP |
500 |
1When the trigger level is exceeded, a shellfish sample should be taken as soon as possible after notification of the trigger level and submitted for analysis for the relevant toxin. In areas that are already subject to a public health warning, levels in excess of these trigger levels may be used to maintain warnings in place without taking further flesh samples.
2For Pseudonitzchia species, when the 100,000 cells/l level is exceeded, a DNA probe or shellfish analysis for domoic acid must be performed. In areas where scallops are present a genetic probe must be done during scallop season before undertaking any flesh analyses for domoic acid. Outside this period, if a flesh sample has been taken of another species this may be analysed for domoic acid instead of undertaking a genetic probe. In areas where scallops are not present, flesh testing of non-scallop species should be done instead of a genetic probe if a flesh sample has already been taken for another reason (usually routine PSP monitoring).
3Karenia brevis has not been isolated in New Zealand to date.
4The Karenia/Karlodinium/Gymnodinium group includes Karenia bidigitata, Karenia brevisulcata, Karenia mikimotoi, Karenia papilionacea, Karenia selliformis, Karlodinium micrum and Gymnodinium impudicum.
Note: If there is evidence of fish kills or RIS in the coastal area. Shellfish analysis for toxins should also be considered.
APPENDIX 2 Phytoplankton sampling instructions
Collecting Phytoplankton samples using the Hose Sampler
Equipment |
|
Hose sampler |
supplied by Cawthron |
Clean bucket |
rinse with seawater |
Sample bottles |
100ml plastic, 2 for each sample taken |
Lugols Iodine |
for preserving one of the samples |
Polystyrene bins |
6-pack chilly bins or cardboard box |
Labels etc |
green Cawthron labels and courier tickets |
Method |
|
Prepare hose |
Remove bung from end |
Collect sample |
Lower weighted end first |
Hold top end securely | |
Retrieve sample |
Replace bung securely in top of tube and pull up. |
Empty water into the bucket |
|
Fill sample bottles |
Lower plastic bottle into bucket leaving a small air space at top. |
Label each bottle clearly with date, site name, phytoplankton site code and whether preserved or not.
Do not refrigerate
Contact: Cawthron phytoplankton laboratory, 0800 80 98 98
Collecting Phytoplankton samples using the van Dorn Bottle
Equipment |
|
van Dorn sampler |
supplied by Cawthron |
Clean bucket |
rinse with seawater |
Sample bottles |
100ml plastic, 2 for each sample taken |
Lugols Iodine |
for preserving one of the samples |
Polystyrene bins |
6-pack chilly bins or cardboard box |
Labels etc |
green Cawthron labels and courier tickets |
Method |
|
Check gear |
Ensure rope is attached correctly, with the weight at bottom, and the messenger weight at the top |
Set up sampler |
Refer to the following instructions and diagram |
Hold top end securely | |
Take sample |
Slowly lower to the desired depth, reading the depth from the rope |
Retrieve sample |
Haul sampler aboard |
Fill sample bottles |
Lower plastic bottle into bucket leaving a small air space at top |
Do not refrigerate
Contact: Cawthron phytoplankton laboratory, 0800 80 98 98
How to set up van Dorn Bottle
Lock bottom end cap open |
Push spring-loaded plunger down Insert bottom loop A into groove in lower block D , securing the loop by guiding plunger hook C into hole in lower block, through the loop |
Lock top end |
Place the top clip B onto rope A, close to block D cap open and clear of knot in loop A to avoid the clip catching on the knot in rope A. Clip B must be able to release freely when loop A is released |
Check rope run |
Ensure main rope is secured at top of plunger, in order to hold bottle vertically during descent |
APPENDIX 3: Suggested wording for media statement
The following phrases may be helpful in describing a marine biotoxin Event in the media. It is best to keep language as simple as possible.
Please use the term “non-commercial” rather than “recreational” in press statements and other forms of communication. Many people gather shellfish for traditional purposes or to provide basic food supplies – these activities are not “recreational”.
Paralytic Shellfish Poisoning (PSP)
“Symptoms of PSP include numbness and tingling around the mouth, face or extremities; difficulty in swallowing or breathing; dizziness; double vision; and, in severe cases, paralysis and respiratory failure. Symptoms usually occur within 12 hours of consuming shellfish.”
Amnesic Shellfish Poisoning (ASP)
“Symptoms of ASP are diarrhoea and vomiting, usually within 24 hours of consuming shellfish, and/or confusion, memory loss and disorientation within 48 hours of consuming shellfish.”
Diarrhetic Shellfish Poison (DSP)
“Symptoms of DSP are diarrhoea, nausea, vomiting and abdominal pain, and usually occur within 12 to 24 hours of eating shellfish.”
Neurotoxin Shellfish Poisoning (NSP)
“Symptoms of NSP include numbness and tingling around the mouth, face or extremities; difficulty in distinguishing hot and cold objects; dizziness, difficulty in swallowing or breathing; and, in severe cases, paralysis. Symptoms usually occur within 12 hours, but may appear up to 24 hours after eating shellfish.”
“When a public warning is issued advising against the collecting and eating of shellfish this means:
• Do not collect bivalve shellfish such as mussels, toheroa, pipi, tuatua, cockles, oysters, scallops; do not collect kina.
• You may take paua and crabs but remove the gut before cooking.
• You may take crayfish, but do not eat the gut. Cook and eat flesh (preferably tail) only.”
“If you are in doubt about the safety of any shellfish you have purchased, please contact the retailer or wholesaler who sold it to you.”
During the scallop season, it is a good idea to add the following statement to all press releases:
“The public are advised NOT to eat the gut and skirt of scallops, even when these shellfish come from areas where there are no biotoxin warnings in place.”
APPENDIX 4: Suggested Wording for GP Letter
Dear Dr
TOXIC SHELLFISH POISONING
The XXX DHB Public Health Unit has issued a warning advising the public not to consume shellfish from the following area: XXX
This warning has been issued because of a bloom of XXX which is associated with XXX shellfish poisoning.
Symptoms of PSP include numbness and tingling around the mouth, face or extremities; difficulty in swallowing or breathing; dizziness; double vision; and, in severe cases, paralysis and respiratory failure. Symptoms usually occur within 12 hours of consuming shellfish.
Or
Symptoms of ASP are diarrhoea and vomiting, usually within 24 hours of consuming shellfish, and/or confusion, memory loss and disorientation within 48 hours of consuming shellfish
Or
Symptoms of DSP are diarrhoea, nausea, vomiting and abdominal pain, and usually occur within 12 to 24 hours of eating shellfish. [Delete those that do not apply]
Medical Practitioners have a vital role in alerting health authorities to the occurrence of potentially serious illness. They should consider the possibility of toxic shellfish poisoning in any case of illness that presents with acute onset of gastrointestinal or neurological symptoms following consumption of shellfish.
Toxic shellfish poisoning is caused by eating shellfish contaminated with toxin produced by toxic algae. Scallops, mussels, oysters, pipi, tuatua and other bivalve shellfish are the main vehicles of transmission, but illness is possible following consumption of crabs, lobsters, crayfish, paua, if the gut is eaten.
Presumptive diagnosis can be made on the history of consumption of shellfish immediately prior to development of clinical symptoms.
Actual or suspected toxic shellfish poisoning is notifiable to the Medical Officer of Health pursuant to the Health Act 1956 as a poisoning arising from chemical contamination of the environment. Medical Practitioners, in particular, should immediately report any suspected cases to the Medical Officer of Health in their local District Health Board. To assist the Medical Officer of Health’s investigation, patients and/or caregivers should be asked to retain samples of suspect shellfish for analysis.
We appreciate your assistance in this important public health matter.
Yours faithfully
APPENDIX 5 Cawthron Institute Phytoplankton Laboratory Sample Submission Form
APPENDIX 6 AgriQuality Shellfish Sample Submission Form
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