A REVIEW OF THE MARINE BIOTOXIN MONITORING PROGRAMME FOR NON-COMMERCIALLY HARVESTED SHELLFISH PART 1: TECHNICAL REPORT A Report for the NZ Ministry of Health Brenda E. Hay Coral M. Grant Dorothy-Jean McCoubrey AquaBio Consultants Ltd P. O. Box 560 Shortland St P.O. Auckland 1 New Zealand [email protected] December 2000 DISCLAIMER This technical resources document was prepared under contract to the New Zealand Ministry of Health. The copyright in the report is owned by the Crown and administered by the Ministry. The views of the author do not necessarily represent the views or policy of the New Zealand Ministry of Health. The Ministry makes no warranty, express or implied, nor assumes any liability or responsibility for the use of or reliance on the contents of this report. Neither AquaBio Consultants Limited, nor any of its employees makes any warranty, express or implied, or assumes any liability or responsibility for use of the technical resource document or its contents by any other person or organisation. For bibliographic purposes, this document should be cited as follows: Hay, B. E., Grant, C. M. & McCoubrey, D-J. (2000) A Review of the marine biotoxin monitoring programme for non-commercially harvested shellfish. Part 1: Technical Report. A report prepared for the NZ Ministry of Health by AquaBio Consultants Ltd. NZ Ministry of Health. This document is available on the NZ Ministry of Health’s Web site: http://www.moh.govt.nz ISBN (Book) 0-478-24348-0 ISBN (Internet) 0-478-24349-9 i ACKNOWLEDGEMENTS We wish to thank all those people, scientists and regulators, who have provided invaluable assistance in the form of information and discussion in the preparation of this report. Special thanks to Penny Truman and Yvonne Galloway from ESR, Kirsten Todd, Lesley Rhodes, Lincoln Mackenzie, and Alison Haywood from Cawthron Institute, Hoe Chang from NIWA, Paul Roberts (Ministry of Health) and the local Health Protection Officers in each area. We are very grateful to Beatriz Reguera (Instituto Español de Oceanografia), Paul Anderson (University of Maine) and Don Richard (Canadian Food Inspection Agency), who spent what must have been many hours reviewing our first draft. Particular thanks to Phil Busby (MAF), who, in addition to commenting on our drafts, provided us with access to many papers and books, and waited patiently for us to return them. Lastly, thanks to Janet Young, of the Ministry of Health, who efficiently provided us with information and feedback, and smoothed the process of this review throughout its course. ii FOREWORD Any review of an on-going monitoring programme runs the risk of being superseded by events subsequent to the period for which data analysis has been undertaken. This review is based on analysis of phytoplankton and shellfish data up to the end of June 1999. Since that time, there has been a major bloom of Gymnodinium catenatum off the western coast of the North Island. In addition, David Stirling of the Institute of Environmental and Scientific Research (ESR), is currently undertaking analysis of archived shellfish samples using LC-MS, which may throw some light on the identity of some of the unexplained acetone screen positive test results. The implications of these additional sets of data have not been considered in this review. Brenda Hay December 2000 iii EXECUTIVE SUMMARY Prior to a major biotoxins event in the summer of 1992-93, New Zealand had no recorded incidence of marine biotoxins of public health significance. A marine biotoxin monitoring programme, covering both commercial and non-commercial shellfish harvesting, has been operating since 1993. The current non-commercial marine biotoxin monitoring programme involves regular sampling at 30 phytoplankton sampling sites and 57 shellfish sampling sites. Data from the commercial biotoxin monitoring programme are also purchased. The programme is designed to monitor for potentially toxic phytoplankton, and for the presence of Neurotoxic Shellfish Poisoning (NSP), Paralytic Shellfish Poisoning (PSP), Amnesic Shellfish Poisoning (ASP) and Diarrhetic Shellfish Poisoning (DSP) (Okadaic acid and dinophysistoxins) toxins at levels that present a risk to human health. Internationally, New Zealand is unusual in having detected a wide range of different biotoxins. In addition to those producing PSP, ASP, NSP and “classic” DSP, pectenotoxin and yessotoxin have been detected in shellfish, and palytoxin in phytoplankton. A range of non-toxic compounds, or compounds of unknown toxicity, have also been found, including gymnodimine, and “Wellington Harbour toxin” (oral toxicity unknown). Compounds that are inferred to have caused Respiratory Irritation Syndrome (RIS) in New Zealand include brevetoxin and the “Wellington Harbour toxin”. The data collected in the marine biotoxin monitoring programme since 1993 presents some challenges to analysis: the data are not independent, and are stratified both spatially and temporally over several different scales. Analysis is further complicated by changes in toxin test methods, and differences in biotoxin accumulation and retention between different shellfish species. Effectively only a small proportion of the data can be used for meaningful quantitative analysis. In very broad overview, the situation in New Zealand with respect to marine biotoxins is characterised by: • Wide distribution of potentially toxin-producing phytoplankton throughout New Zealand. • Periods of low frequency of biotoxin occurrence followed by periods of higher biotoxin occurrence, generally in relatively localised areas. Biotoxins may then persist in a localised area for a period of time, sometimes in one shellfish species/at one location. • Possible seasonal patterns in the occurrence of some biotoxins in shellfish (for example, NSP and ASP), and not in others. • In periods of low biotoxin activity, some toxins are present very rarely (e.g. NSP toxins) and others are common at low levels in some areas (e.g. Domoic acid). • Possible differences in the accumulation and retention of biotoxins by different New Zealand shellfish species. These differences are potentially significant in terms of the risk of Toxic Shellfish Poisoning (TSP) to consumers. Currently there is a poor understanding, both here and internationally, of the factors influencing the occurrence of toxic phytoplankton blooms. There is insufficient iv information to be able to predict the future occurrence of marine biotoxins in New Zealand with confidence. The potential risks presented by marine biotoxins in New Zealand are not distributed evenly across the population. There is a disproportionate potential impact on sectors of the population that consume more non-commercially harvested shellfish (for example, Maori, and possibly Pacific and Asian peoples), on older people or people in poor health, and on asthmatics. The potential risks of TSP are distributed geographically with availability of desirable shellfish for harvest. There have been few studies undertaken on non-commercial shellfish harvesting in New Zealand, and there are significant discrepancies between the results of the studies. There are limited good quality epidemiological data for TSP in New Zealand: although 457 cases potentially related to TSP have been reported between January 1993 and June 1999, only 9 (1.97%) have been classed as probable cases of TSP. There are no confirmed cases under the current case definitions. The oral toxicity of some of the marine biotoxins found in New Zealand, including the effect of long-term ingestion of low levels of toxin, are still unknown. The current outcome surveillance may not detect these impacts. Lack of robust data severely limits quantitative assessment of the risks associated with biotoxins in New Zealand. There are sufficient data to suggest that in the absence of a non-commercial biotoxin monitoring programme, a significant number of people could become ill as a result of TSP in some years. Some of these people would be severely ill, with the risk of death. For example, one scenario suggests that 50% of the PSP cases (amounting to nearly 2000 people in a scenario relating to the Bay of Plenty) would have moderate to severe symptoms. The long-term effects of ingestion of “DSP” toxins, including Okadaic acid, dinophysistoxins, yessotoxin and pectenotoxin, are unknown, but potentially present a risk. The incidences of these two latter toxins are unknown because they are not currently included in the monitoring programme. The levels of Domoic acid detected in shellfish to date would only produce relatively mild symptoms of ASP in adults (although one scenario suggests that up to 750 people could be affected). The potential impact of NSP remains somewhat unknown due to a lack of robust data on shellfish toxicity levels from the 1993 event, but has been very low in subsequent years. RIS events have occurred in two of the last six years, and depending on wind strength and direction, affect anyone within a few kilometres of the coast. Asthmatic people are the most seriously affected, and data suggest that approximately 9.8% of people exposed to RIS toxins in New Zealand could potentially suffer an asthma attack as a result. Within the strategic framework for public health, and the global context of developments relating to marine biotoxins, a range of broad issues relating to the management of marine biotoxins in New Zealand require consideration. These encompass both strategic and technical issues. It is suggested that a more proactive, strategic approach to the collection