Next Article in Journal
c-Jun N-Terminal Kinase Phosphorylation Is a Biomarker of Plitidepsin Activity
Next Article in Special Issue
Climate Variability and Oceanographic Settings Associated with Interannual Variability in the Initiation of Dinophysis acuminata Blooms
Previous Article in Journal
Use of Okadaic Acid to Identify Relevant Phosphoepitopes in Pathology: A Focus on Neurodegeneration

Mar. Drugs 2013, 11(5), 1669-1676; doi:10.3390/md11051669

Article
Outbreak of Diarrhetic Shellfish Poisoning Associated with Mussels, British Columbia, Canada
Marsha Taylor 1,*, Lorraine McIntyre 1, Mark Ritson 2, Jason Stone 3, Roni Bronson 4, Olga Bitzikos 2, Wade Rourke 5, Eleni Galanis 1,6 and Outbreak Investigation Team
1
British Columbia Centre for Disease Control, 655 W 12 Ave, Vancouver, British Columbia, V5Z 4R4, Canada; E-Mails: lorraine.mcintyre@bccdc.ca (L.M.); eleni.galanis@bccdc.ca (E.G.)
2
Vancouver Coastal Health Authority, Vancouver, British Columbia, V5Z 4C2, Canada; E-Mails: mark.ritson@vch.ca (M.R.); olga.bitzikos@vch.ca (O.B.)
3
Fraser Health Authority, Suite 400, Central City Tower, 13450-102nd Avenue, Surrey, British Columbia, V3T 0H1, Canada; E-Mail: jason.stone@fraserhealth.ca
4
Health Canada, C417, Frederick G Banting Bldg, Ottawa, Ontario, K1A 0K9, Canada; E-Mail: roni.bronson@hc-sc.gc.ca
5
Dartmouth Laboratory, Canadian Food Inspection Agency, 1992 Agency Drive, Dartmouth, Nova Scotia, B3B 1Y9, Canada; E-Mail: wade.rourke@inspection.gc.ca
6
School of Population and Public Health, University of British Columbia, 2206 East Mall, Vancouver, British Columbia, V6T 1Z3, Canada
Outbreak Investigation Team (alphabetically): Hanna Bailey (Canadian Food Inspection Agency); Keir Cordner (Vancouver Island Health Authority); Mark Feeley (Health Canada); Joe Fung (BC Public Health Microbiology and Reference Laboratory); Murray Fyfe (Vancouver Island Health Authority); Kelly Hislop (Health Canada); Virginia Jorgenson (Vancouver Coastal Health Authority); Deidre Kelly (Canadian Food Inspection Agency); Perry Kendall (BC Ministry of Health); Dan Moreau (Vancouver Island Health Authority); Craig Nowakowski (Vancouver Island Health Authority); Luc Pelletier (Health Canada); Helena Swinkels (Fraser Health Authority); Julie Wong (BC Public Health Microbiology and Reference Laboratory); André Youssef (Canadian Food Inspection Agency); Sussan Zarepourarzil (Canadian Food Inspection Agency).
*
Author to whom correspondence should be addressed; E-Mail: marsha.taylor@bccdc.ca; Tel.: +1-604-707-2544; Fax: +1-604-707-2516.
Received: 12 March 2013; in revised form: 5 April 2013 / Accepted: 19 April 2013 /
Published: 21 May 2013

Abstract

: In 2011, a Diarrhetic Shellfish Poisoning (DSP) outbreak occurred in British Columbia (BC), Canada that was associated with cooked mussel consumption. This is the first reported DSP outbreak in BC. Investigation of ill individuals, traceback of product and laboratory testing for toxins were used in this investigation. Sixty-two illnesses were reported. Public health and food safety investigation identified a common food source and harvest area. Public health and regulatory agencies took actions to recall product and notify the public. Shellfish monitoring program changes were implemented after the outbreak. Improved response and understanding of toxin production will improve management of future DSP outbreaks.
Keywords:
diarrhetic shellfish poisoning (DSP); outbreak; Canada; shellfish toxins; mussels; okadaic acid; public health

1. Introduction

Diarrhetic Shellfish Poisoning (DSP) is caused by consuming sufficient amounts of okadaic acid (OA) group toxins, including OA, dinophysistoxin-1, and 2 (DTX-1, and DTX-2), which are produced by dinoflagellate algae (Dinophysis spp., Prorocentrum spp.) [1,2], and dinophysistoxin-3 (DTX-3). DTX-3 refers to the fatty acid esters of OA, DTX-1 or DTX-2 and is found in phytoplankton and is also a product of shellfish metabolism [3,4,5]. The triggers for toxin production are unclear. Shellfish consume the algae and accumulate the heat stable, lipophilic toxins [6].

DSP is characterized by symptoms of nausea, vomiting, diarrhea, chills and abdominal pain [2]. The incubation period ranges from 30 min to 12 h and symptoms may last up to 3 days [7]. Chronic sequelae have not been reported, although there is very little known about possible health effects associated with chronic exposure to OA-group toxins or long term impact of acute intoxication [1,2,8]. The majority of DSP outbreaks have been reported outside of North America [2,6] but outbreaks and toxin detections (primarily DTX-1) have been reported from eastern Canada [9,10]. Although DTX-1 had been detected in the Northeastern Pacific marine sponge from British Columbia (BC) coastal waters, there were no confirmed reports of DSP prior to this outbreak [11]. Shellfish samples epidemiologically linked to illness are tested for lipophilic shellfish toxins (LSTs include OA-group toxins, pectenotoxins, azaspiracids, yessotoxins, and cyclic imine toxins), but clinical samples are not analysed for these toxins in Canada.

OA-group toxins are monitored as part of the LSTs to meet Canadian Shellfish Sanitation Program requirements [12]. LSTs have been monitored in select BC sites since 2004 and the LST monitoring was expanded in 2011. Affected areas are closed to harvesting when action levels are exceeded [12]. As of July, 2011 the Health Canada (HC) action level for DSP toxins was 0.20 μg/g for the sum of OA and DTX-1 in edible shellfish tissue. DTX-2 and DTX-3 were not included in the action level prior to August, 2011.

Monitoring DTX-3 directly in a regulatory laboratory is challenging because it may include many different compounds, but DTX-3 may be monitored indirectly by including either an enzymatic [13] or alkaline hydrolysis [14] step to remove the fatty acid esters and allow detection of the parent compound. The DTX-3 concentration is then calculated as the difference between the parent compound concentrations in the hydrolysed and unhydrolysed portions of the sample.

This paper describes a DSP outbreak in BC and outlines further areas of study to improve understanding and ability to investigate future outbreaks.

2. Methods

Public health authorities collect clinical and exposure information using a standard surveillance form [15]. Surveillance for shellfish related illness is often based on clusters and not at the individual level. During this investigation, clusters reported to public health and the implicated food premises (restaurant or retail) were investigated to determine the source of the mussels and collect supplier information. A food safety traceback is conducted by tracking a food product from the retail level through distribution to the production or processing facilities to find the suspected source. The Canadian Food Inspection Agency (CFIA) conducted a traceback investigation using information collected from the food premises and provided HC with analytical results for OA-group toxins in mussel samples from the harvest area on August 5 and 6, 2011 for risk assessment.

The BC Public Health Microbiology and Reference Laboratory tested leftover food samples from implicated food premises for enteric pathogens and tested stool samples for norovirus and bacteria from individuals who were symptomatic and consumed the mussels. The CFIA tested shellfish samples from the implicated harvest area for LSTs using liquid chromatography-mass spectrometry (LC-MS/MS) [16], including an alkaline hydrolysis procedure to detect DTX-3 [14].

3. Results

On August 3, 2011, public health officials in two BC regional health authorities were notified of gastrointestinal illness among individuals who had consumed cooked mussels at different restaurants between July 28 and August 2. Information on symptoms, incubation period, and consumption of cooked products in various locations led to the hypothesis that DSP was the cause of illness. Restaurants receiving customer complaints notified the shellfish industry (harvester and processors) of the reported illnesses. The harvester took steps to withdraw product on August 3.

Sixty-two clinical cases associated with 15 food premises in three health authorities were reported. All cases reported consuming cooked mussels between July 28 and August 6. The most common symptoms were diarrhea, nausea, vomiting, abdominal pain and cramps. The incubation period ranged from 5 to 15 h and symptoms lasted 1 to 3 days.

The food safety investigation and traceback identified a single harvest area at the north end of the Strait of Georgia (Figure 1) and a single mussel harvester. The harvest dates of implicated mussels were between July 24 and 31. OA-group toxin results of mussel samples from this harvest area are presented in Table 1. Two samples were reported above the action level of 0.2 μg/g for the sum of OA and DTX-1. Monitoring results demonstrated that concentrations of OA-group toxins in mussel samples were below the action level after August 8. Interestingly, DTX-3 was the most prominent toxin detected and was present in all mussel samples harvested after July 19. Two mussel samples and two sauces served with mussels at implicated restaurants tested negative for enteric pathogens. Six clinical stool samples were negative for norovirus and enteric pathogens.

Marinedrugs 11 01669 g001 1024
Figure 1. Location of harvest area associated with Diarrhetic Shellfish Poisoning (DSP) outbreak, British Columbia (BC), August 2011.

Click here to enlarge figure

Figure 1. Location of harvest area associated with Diarrhetic Shellfish Poisoning (DSP) outbreak, British Columbia (BC), August 2011.
Marinedrugs 11 01669 g001 1024
Table Table 1. Okadaic acid (OA)-group toxin results from implicated harvest area, June–August 2011, BC, Canada.

Click here to display table

Table 1. Okadaic acid (OA)-group toxin results from implicated harvest area, June–August 2011, BC, Canada.
ShellfishHarvest dateLaboratory report dateOA (μg/g)DTX-1 (μg/g)DTX-3 (μg/g)
MusselJune 21June 28NDNDND
MusselJuly 5July 14ND0.090.08
MusselJuly 12July 20ND0.12ND
MusselJuly 19July 27ND0.180.23
MusselJuly 31August 6ND0.210.26
MusselAugust 2August 60.010.230.45
MusselAugust 2August 6ND0.080.35
MusselAugust 2August 6ND0.140.72
MusselAugust 4August 5ND0.100.26
MusselAugust 8August 13ND0.090.06
MusselAugust 17August 24ND0.080.05

ND: Not detected above limit of quantitation (0.01 μg/g OA or 0.03 μg/g DTX-1); Note: DTX-2 was not identified in any analysed sample.

In addition to the harvester-led withdrawal of product on August 3, a harvest-area closure was recommended by the CFIA on August 5 based on OA-group toxin concentrations. On August 6, a health hazard alert recalling all implicated mussels harvested from the area was issued by the CFIA based on a HC risk assessment. The area was re-opened on August 24 following established procedures [10].

4. Discussion

Algal blooms leading to OA-group toxin production and shellfish contamination are increasing worldwide [2,6,17]. Although the causes for this increase are not clear, environmental factors such as climate change and projected increases to ocean temperatures, reduction in pH and increasing availability of nitrate may lead to increasing algal blooms. Increased marine traffic and global sales of spats for cultivation have been proposed as possible reasons for the emergence of toxic algal species in new areas. In addition, social factors such as an increased consumption of seafood, or improved regulatory standards and monitoring to identify toxins and human illnesses may also have impact on this apparent increasing trend [2,17,18]. The trigger for toxin production that led to this outbreak is unknown and further study in consultation with experts is needed.

Washington State public health authorities also reported DSP cases in June, 2011 [19]. The cases also consumed mussels with high concentrations of DTX-1. Retrospectively, the similarity in timing and location of cases may suggest a common ecological reason for the emergence of OA-group toxins in Pacific Northwest coastal waters in 2011. Timely communication between departments and jurisdictions that share coastal waters will ensure that each is aware in the case of future events.

There is international variation in OA-group toxin action levels and laboratory testing methods [1,6,20]. Regulatory testing most commonly employs LC-MS/MS or a mouse bioassay (to be suspended by the European Union after 2014). LC-MS/MS methods offer greater sensitivity and the ability to identify and quantify specific toxins and will be the primary method used internationally [1]. Canadian biotoxin monitoring is based on results of shellfish samples harvested from established sites. Some jurisdictions monitor phytoplankton levels in harvest-area water in addition to toxins in shellfish [6] and based on 2011 data from BC this approach was suggested by Esenkulova et al. to provide earlier warnings compared to biotoxin monitoring alone [21]. While some research has indicated a relationship between the increased concentration of phytoplankton and the toxin there have also been limitations noted [6,22,23]. The potential value of phytoplankton monitoring to compliment current LST monitoring in order to provide information on potential harmful algal blooms that may affect shellfish and human health and could lead to an earlier and reliable response in BC could be explored in collaboration with researchers and industry.

A review of all HC marine biotoxin action levels was already in progress as of 2011, and an interim action level of 0.20 μg for the sum of OA, DTX-1, DTX-2 and DTX-3 per gram of edible shellfish tissue was provided by HC after reviewing LST results from this investigation [24]. Significant DTX-3 concentrations had not been detected in Canadian shellfish previously. Monitoring concentrations of DTX-3 is relevant because it may be present in higher concentrations than other OA-group toxins, as in our situation. In addition, there are indications that it can be hydrolysed to its parent compound in the gastrointestinal tract of humans [25]. Results from this DSP outbreak led to increasing the number of monitoring sites and sampling frequency in BC and the program has the capacity to expand and prioritize samples as necessary. Monitoring results are also provided to the shellfish industry as they become available [26]. These program changes in BC should further minimise the potential risk of contaminated shellfish entering commercial markets. Ongoing communication between jurisdictions and organizations as well as an understanding of factors contributing to OA-group toxin production should lead to improved identification and management in the event of a DSP outbreak.

There is limited information on the epidemiology of human illness caused by OA-group toxins. Improvements in identification and surveillance of human illness, understanding of exposures, dose-response, severity of illness and chronic sequelae will improve our understanding of the burden of disease and ability to communicate on the risks associated with DSP, which may lead to better public health information and response.

5. Conclusions

This DSP outbreak in BC was a significant event with 62 clinical illnesses reported and rapid action to identify and remove the source of illness. The intersectoral and collaborative approach to human illness surveillance and response to shellfish-related illnesses in BC led to rapid mitigation. Modifications to the monitoring program, which have already been implemented, will reduce the risk of DSP. Identifying factors contributing to toxin production could direct future monitoring plans.

Acknowledgments

The authors would like to acknowledge representatives from Fraser Health Authority, Vancouver Coastal Health Authority, Vancouver Island Health Authority and the CFIA for their involvement in this investigation, representatives from HC for their work in conducting the risk assessment and Sunny Mak from the BCCDC for his assistance in creating Figure 1.

Conflict of Interest

The authors declare no conflict of interest.

References

  1. European Food Safety Authority. Marine biotoxins in shellfish—Okadaic acid and analogues. EFSA J. 2008, 589, 1–62.
  2. James, K.J.; Carey, B.; O’Halloran, J.; van Pelt, F.N.A.M.; Škrabáková, Z. Shellfish toxicity: Human health implications of marine algal toxins. Epidemiol. Infect. 2010, 138, 927–940. [Google Scholar] [CrossRef]
  3. MacKenie, L.; Holland, P.; McNabb, P.; Beuzenberg, V.; Selwood, A.; Suzuki, T. Complex toxin profiles in phytoplankton and Greenshell mussels (Perna canaliculus), reveladed by LC-MS/MS analysis. Toxicon 2002, 40, 1321–1330. [Google Scholar] [CrossRef]
  4. Vale, P.; Sampayo, M.A.M. First confirmation of human diarrhoeic poisonings by okadaic acid esters after ingestion of razor clams (Solen marginatus) and green crabs (Carcinus maenas) in Averito lagoon, Portugal and detection of okadaic acid esters in phytoplankton. Toxicon 2002, 40, 989–996. [Google Scholar] [CrossRef]
  5. Rossignoli, A.E.; Fernandez, D.; Regueiro, J.; Marino, C.; Blanco, J. Esterification of okadaic acid in the mussel Mytilus galloprovincialis. Toxicon 2011, 57, 712–720. [Google Scholar] [CrossRef]
  6. Food and Agriculture Organization of the United Nations. FAO Food and Nutrition Paper. Marine Biotoxins, Available online: http://www.fao.org/docrep/007/y5486e/y5486e00.htm#Contents (accessed on 2 February 2012).
  7. Fleming, L. Diarrhetic Shellfish Poisoning. Available online: http://www.whoi.edu/science/B/redtide/illness/dsp.html (accessed on 2 February 2012).
  8. Fleming, L.E.; Bean, J.A.; Baden, D.G. Epidemiology of Toxic Marine Phytoplankton. Unesco IOC Manual on Hamrful Marine Phytoplankton #33; UNESCO: Paris, France, 1995; pp. 475–488. Available online: http://yyy.rsmas.miami.edu/groups/niehs/mfbsc/science/pdf/Epidemiology%20of%20Toxic%20Marine%20Phytoplankton.pdf (accessed on 15 November 2012). [Google Scholar]
  9. Quilliam, M.A.; Gigan, M.W.; Pleasance, S.; Defreitas, A.S.W.; Dougals, D.; Fritz, L.; Hu, T.; Marr, J.C.; Smyth, C.; Wright, J.L.C. Confirmation of an incident of Diarrhetic Shellfish Poisoning in Eastern Canada. In Toxic Phytoplankton Blooms in the Sea; Smayda, T.J., Shimizu, Y., Eds.; Elsevier Science Publishers: Amsterdam, The Netherlands, 1993; pp. 547–552. [Google Scholar]
  10. Todd, E.C. Seafood-associated diseases and control in Canada. Rev. Sci. Tech. 1997, 16, 661–672. [Google Scholar]
  11. Britton, R.; Roberge, M.; Brown, C.; van Soest, R.; Andersen, R.J. New okadaic acid analogues from the marine sponge Merriamum oxeato and their effect on mitosis. J. Nat. Prod. 2003, 66, 838–843. [Google Scholar] [CrossRef]
  12. Canadian Food Inspection Agency. Control of Marine Biotoxins. Canadian Shellfish Sanitation Program, Available online: http://www.inspection.gc.ca/english/fssa/fispoi/man/cssppccsm/chap11e.shtml (accessed on 2 February 2012).
  13. Doucet, E.; Ross, N.N.; Quilliam, M.A. Enzymatic hydrolysis of esterified diarrhetic shellfish poisoning toxins and pectenotoxins. Anal. Bioanal. Chem. 2007, 389, 335–342. [Google Scholar] [CrossRef]
  14. Mountfort, D.O.; Suzuki, T.; Truman, P. Protein phosphatase inhibition assay adapted for determination of total DSP in contaminated mussels. Toxicon 2001, 39, 383–390. [Google Scholar] [CrossRef]
  15. BC Shellfish Related Illness Surveillance Form. Available online: http://www.bccdc.ca/NR/rdonlyres/66BC1337-C0A1–46FF-8D16–89D737432427/0/EPI_Form_Shellfish_20100804.pdf (accessed on 2 February 2012).
  16. Canadian Food Inspection Agency. Analysis of Lipophilic Shellfish Toxins by Liquid Chromatography/Mass Spectrometry. Canadian Food Inspection Agency: Dartmouth, Canada, 2011.
  17. Fleming, L.E.; Broad, K.; Clement, A.; Dewailly, E.; Elmir, S.; Knap, A.; Pomponi, S.A.; Smith, S.; Solo Gabriele, H.; Walsh, P. Oceans and human health: Emerging public health risks in the marine environment. Mar. Poll. Bull. 2006, 53, 545–560. [Google Scholar] [CrossRef]
  18. Fleming, L.; Baden, E.; Bean, J.A.; Weiman, R.; Blythe, D.G. Seafood Toxin Diseases: Issues in Epidemiology and Community Outreach. Harmful Algae; Xunta de Galicia and Intergovernmental Oceanographic Commission of UNESCO: Galicia, Spain, 1998; pp. 245–248. Available online: http://www. oceandocs.org/bitstream/1834/758/1/Lora%20E5.pdf (accessed on 15 November 2012). [Google Scholar]
  19. Lloyd, J. Personal communication, Seattle & King County Public Health: Seattle, WA, USA, 2010.
  20. The Center for Food Safety and Applied Nutrition, US FDA. Bad Bug Book: Foodborne Pathogenic Microorganisms and Natural Toxins Handbook, Various Shellfish-Associated Toxins. Available online: http://www.fda.gov/Food/FoodSafety/FoodborneIllness/FoodborneIllnessFoodbornePathogensNaturalToxins/BadBugBook/ucm070795.htm (accessed on 2 February 2012).
  21. Esenkulova, S.; Haigh, N. First report of Dinophysis species causing Diarrhetic Shellfish Poisoning in British Columbia, Canada. HAN 2012, 45, 16–17. [Google Scholar]
  22. Sidari, L.; Nichetto, P.; Cok, S.; Sosa, S.; Tubaro, A.; Honsell, G.; Della Loggia, R. Phytoplankton detection and DSP toxicity: Methodological considerations. J. Appl. Phycol. 1995, 7, 166–169. [Google Scholar]
  23. Van der Fels-Klerx, H.J.; Adamse, P.; Goedhart, P.W.; Poelman, M.; Pol-Hofstad, I.E.; van Egmond, H.; Gerssen, A. Monitoring phytoplankton and marine biotoxins in production waters of the Netherlands: Results after one decade. Food Addit. Contam. 2012, 29, 1616–1629. [Google Scholar] [CrossRef]
  24. Health Canada. Canadian Standard (Maximum Levels) for Various Chemical Contmainants in Foods. Available online: http://www.hc-sc.gc.ca/fn-an/securit/chem-chim/contaminants-guidelines-directives-eng.php (accessed on 26 July 2012).
  25. García, C.; Truan, D.; Lagos, M.; Santelices, J.P.; Diaz, J.C.; Lagos, N. Metabolic transformation of dinophysistoxin-3 into dinophysistoxin-1 causes human intoxication by consumption of O-acyl-derivates dinophysistoxins contaminated shellfish. J. Toxicol. Sci. 2005, 30, 287–296. [Google Scholar] [CrossRef]
  26. Canadian Food Inspection Agency. Canadian Shellfish Sanitation Program and the CFIA Marine Biotoxin Program in BC. Available online: http://www.bccdc.ca/NR/rdonlyres/FBFBB050-B2B1-4934-8253-81D4A1652C4E/0/Deirdre_MonitoringPrograms.pdf (accessed on 8 May 2013).
Mar. Drugs EISSN 1660-3397 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert