Monitoring and controlling viral contamination of shellfish

Transcription

1 Bill Doré Monitoring and controlling viral contamination of shellfish Marine Institute -National Reference Laboratory 1

2 Presentation Overview Why do we have a problem with viruses in bivalve molluscan shellfish? e.g. Mussels, cockles, & oysters Current control measures Progress and challenges for setting an international regulatory standards for viruses in bivalve shellfish Method standardisation Balancing Industry Impact and health benefits Risk management procedures used by the shellfish industry. 2

3 Shellfish, Sewage and Public Health Shellfish growing areas may also be impacted by sewage Shellfish feed by filtration Sewage-derived pathogens are concentrated Shellfish are eaten raw or lightly cooked Outbreaks of disease can occur 3

4 Shellfish European Control Measures WF Directive 2000/60/EC EU reg. 2004/854 EU reg. 2004/853 EU reg. 2004/853 Control of sewage pollution in shellfisheries Classification and monitoring of harvesting areas Commercial processing (depuration, relaying, cooking) End-product controls (quality tests, traceability) 4

5 Controls in Europe have virtually eliminated bacterial illness associated with shellfish consumption. However the risk of virus illness remains and outbreaks of illness continue to occur throughout Europe. 5

6 Virus illness outbreaks caused by oysters Scandinavia, Jan 1997 (J. of Shell. Res. 17(5): ) Gastro-enteritis associated with oysters Denmark: 356 cases recorded (Sweden, Netherlands and Germany) Approx. 35,000 contaminated oysters sold in Denmark alone Europe Jan/March 2010 (Euro Surveill. 15(12): 1-5) 334 cases in 65 clusters in Sweden, UK, Norway, France and Denmark Oysters produced in France, UK and Ireland Winter 2010 cold and high gastro-enteritis activity in community 6

7 Virus illness outbreaks caused by oysters Scandinavia, Jan 1997 (J. of Shell. Res. 17(5): ) Gastro-enteritis associated with oysters Denmark: 356 cases recorded (Sweden, Netherlands and Germany) Approx. 35,000 contaminated oysters sold in Denmark alone Europe Jan/March 2010 (Euro Surveill. 15(12): 1-5) 334 cases in 65 clusters in Sweden, UK, Norway, France and Denmark Oysters produced in France, UK and Ireland Winter 2010 cold and high gastro-enteritis activity in community 7

8 Norovirus Relatively mild gastroenteritis (2-4 days) nausea, diarrhoea, vomiting, fever and abdominal pain The most common cause of infectious intestinal disease in the community Seasonal distribution Winter Vomiting Disease Coincides with peak periods for oyster consumption Genetically diverse virus with two main genogroups (GI, GII) and many genotypes that infect humans. 8 Detection methods

9 Norovirus Person to person spread Highly infectious (<10 virus particles) Easily spread in closed communities Cruise ships, hospitals, care homes, schools.. 9 Food safety challenges: Controlling Foodborne Viruses. Dublin Dec1st 2015 Vomiting Larry

10 Role of shellfish in the spread of NoV? recombination person-to-person spread Virus shedding in feaces: viral particles/g new variant Discharge to the environment contaminated with multiple strains Global trade 10 Shellfish (oysters)

11 11 Food safety challenges: Controlling Foodborne Viruses. Dublin Dec1st 2015

12 Virus Controls in shellfish Despite the recognised risk there are currently no EU regulatory standards for viruses in shellfish Until recently there has been a lack of reliable methods for the detection and quantification of viruses in shellfish (and other foods) NoV not culturable Sensitivty (low target numbers) Strain diversity 12

13 NoV detection in shellfish ISO/TS : published March 2013 Quantitative real-time RT-PCR method for norovirus (GI & GII) and hepatitis A in shellfish Developed by European working group (CEN) lead by EURL and including MI Also bottled water, hard surfaces, soft fruit and salad vegetables Marine Institute -accredited to ISO17025 standard in 2010 for the real-time RT-PCR method An internationally recognised standard method is the first step towards establishing a standard for Nov in shellfish? 13

14 fwefergergeththffsr qqqqq 2g of digestive glands, add equal vol. of proteinase K, 37 C and 60 and centrifuge 14 Food safety challenges: Controlling Foodborne Viruses. Dublin Dec1st 2015

15 Norovirus Controls-European Context EFSA scientific opinion on Norovirus in oysters: methods, limits and control options managers should consider establishing an acceptable limit for NoV in oysters to be harvested and placed on the market European Commission DG-Sanco Working Group on Live Bivalve Molluscs Includes discussions on virus control measures (standards) 15

16 NoV detection by PCR what does it mean? Detects short genome fragments from both infectious and non-infectious virus particles NoV often detected in oysters in the absence of any apparent illness (outbreaks) UK study 76% of oysters contain NoV but 52% of these oysters contained concentrations <LOQ of the assay Lowther et al (2012) Appl. Environ Microbiol Aug; 78(16): This makes setting a standard (acceptable limit) for NoV in oysters difficult Impact on industry vs public health benefit 16

17 Benefit (food safety) Cost (industry impact) Benefit (difficult) Dose Response Outbreak data 17 Calculating the balance Cost (relatively easy) NoV concentration in oysters European baseline survey

18 EU wide Baseline Study EFSA & EURL are currently establishing protocols for European wide survey across shellfish areas to establish the distribution of NoV in oysters across European shellfish. Aim To gather information on the extent of NoV contamination in European oysters Establish the impact for industry of the introduction of a NoV standard in Europe Will not establish a safe or acceptable limit for NoV in shellfish will not gather illness data will not establish a threshold of infection will not determine exposure levels for consumers 18

19 Survey of Market Ready Oysters Project with UCD (part funded by Food for Health Research Initiative Contract 07FHRIT AFRC5) 8 companies/suppliers C. gigas (1 site both C. gigas and O. edulis) Depurated or Category A Monthly sampling between Jan 2012 and March 2013 Total of 114 samples 19

20 NoV (GI & GII) concentration in market ready oysters Overall Percentage detection rates (n=114) Not detected Positive >200 >500 >

21 Benefit (food safety) Cost (industry impact) Benefit (difficult) Dose Response Outbreak data 21 Calculating the balance Cost (relatively easy) NoV concentration in oysters European baseline survey

22 Dose response (published information) A few published human volunteer studies with a range of 50% human infectious dose reported 18-1,015 genome copies (Teunis et al 2008) 1,320-2,800 genome copies (Atmar et al 2014) Published outbreak data Host susceptibility and immunity Secretor positive individuals Genotype Differences? 22

23 Outbreak Information Date No. ill NoV Levels (GI+GII) Comments Feb 2010 Jan 2012 >70 Restaurants 2,350 & 2040 A number of illnesses clusters in Harvest area 2,890 &1,920 Ireland and UK 18 Restaurant 2,380 Dublin Restaurant Harvest area 4,000 Feb 2012 Nov Restaurant 1,446-4,413 Illness in Denmark Harvest area 1,074 Restaurant results from Danish NRL. RASSF <10 Restaurant 433 Galway Restaurant. Harvest area 926; 2,775 Dredged Oysters 23

24 NoV (GI & GII) Concentration in Market Ready Oysters and Oysters Associated with Outbreaks NoV copies g -1 Threshold of infection remains undetermined Dose response Increasing concentration of NoV = increasing risk of apparent infection (outbreaks) Sample (n=162) 24

25 FIRM Funded Project NORORISK -developing a risk assessment framework for NoV in Irish oyster areas 25

26 Risk Assessment Project Three year project funded under FIRM with UCD and Marine Institute Establish a Risk Assessment Framework for Norovirus in Irish Oyster Production Areas Use a sample area to develop a framework Develop exposure model using data from sample area Assess impact of management interventions (e.g. depuration) on NoV concentrations Run published dose response models to estimate disease Framework will provide a model that can be applied to other areas 26

27 NoV concentrations in individual oysters Measured NoV (GII) concentration in 30 individual oysters from one growing bag Repeated at low (~LOQ), medium and high NoV concentrations Estimate potential range of consumer exposures based on individual oyster concentrations estimate 27

28 Concentration of NoV GII per g in individual shellfish Mean=88.2 Range= Mean=328.8 Range= Mean= Range =

29 Consumer Exposure 95% interval for Norovirus genome copies consumed per meal size Oysters eaten Copies/g = 85 Copies/g = 325 Copies/g = (0-428) (47-661) ( ) ( ) ( ) 598 ( ) 1196 ( ) 1794 ( ) 2388 ( ) 2988 ( ) 2516 ( ) 5062 ( ) 7605 ( ) ( ) ( ) 29

30 Drivers for NoV standards in shellfish Food Safety (regulation) outbreaks EFSA opinion DG Sanco WG 30

31 Drivers for NoV standards in shellfish Food Safety (regulation) Business outbreaks outbreaks EFSA opinion retailers 31 DG Sanco WG importing countries

32 Risk Management MI worked with a number of producers to implement risk management procedures 1. Characterisation of harvest areas Identification of pollution risks in production areas NoV concentrations (monitoring) 2. Identification of high risk periods Season, community outbreaks and high rainfall events Nov monitoring (increase in NoV concentrations) 3. Determine effectiveness of post harvest treatment depuration (elevated temp and extended time) Relay in areas of clean seawater? 32

33 Boxplot of of NoV concentrations in oysters 5000 Genome concnetrations per g Area 1 Area 2 Dep.

34 Viruses & Shellfish Summary (1) Sewage contamination of bivalve shellfish is a significant public health concern EU regulation controls bacterial risks but there remains a risk from viruses In Ireland the most clearly identified risk is NoV in oysters A standardised quantitative test method for the detection of NoV is available (ISO/TS ) Robust and reliable method to quantify NoV in oysters (and other foods) does not distinguish between non-infectious and infectious virus particles 34

35 Viruses & Shellfish Summary (2) A recognised need to set a regulatory standard for NoV in oysters Threshold of infection is not known but a dose response exists (increasing genome copies increasing risk) Balance of cost (industry impact) against benefit (food safety gains) EU wide baseline study to establish industry impact UCD/MI risk assessment project Industry risk management practice Identify control points points and develop risk management plans NoV monitoring is of major risk management tool Export market key driver 35

36 Acknowledgements Marine Institute Sinead Keaveney Agnieszka Rupnik Leon Devilly UCD (risk assessment project) Francis Butler Kevin Hunt 36