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Transcript of Monitoring and controlling viral contamination of shellfish · Monitoring and controlling viral...
Monitoring and controlling viral
contamination of shellfish
Bill Doré
Marine Institute -National Reference Laboratory
Food safety challenges: Controlling Foodborne Viruses. Dublin Dec1st 2015
1
Presentation Overview
Food safety challenges: Controlling Foodborne Viruses. Dublin Dec1st 2015 2
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.
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
4
Shellfish European Control Measures
Control of sewage pollution in
shellfisheries
Classification and monitoring
of harvesting areas
Commercial processing
(depuration, relaying, cooking)
End-product controls
(quality tests, traceability)
EU
reg.
2004/8
53
EU
reg.
2004/8
54
WF
Directive
2000/6
0/E
C
EU
reg.
2004/8
53
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……….
Food safety challenges: Controlling Foodborne Viruses. Dublin Dec1st 2015
Virus illness outbreaks caused by oysters
6
Scandinavia, Jan 1997 (J. of Shell. Res. 17(5):1633-1635)
– 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
Food safety challenges: Controlling Foodborne Viruses. Dublin Dec1st 2015
Virus illness outbreaks caused by oysters
7
Scandinavia, Jan 1997 (J. of Shell. Res. 17(5):1633-1635)
– 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
Food safety challenges: Controlling Foodborne Viruses. Dublin Dec1st 2015
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.
Detection methods
8
Food safety challenges: Controlling Foodborne Viruses. Dublin Dec1st 2015
Norovirus
Food safety challenges: Controlling
Foodborne Viruses. Dublin Dec1st 2015
9
Person to person spread
Highly infectious (<10 virus particles)
Easily spread in closed communities
Cruise ships, hospitals, care homes, schools…..
Vomiting Larry
Role of shellfish in the spread of NoV?
Global trade contaminated with multiple strains
Shellfish (oysters)
Discharge to the environment
person-to-person spread
Virus shedding in feaces:
104-1010 viral particles/g
new variant
recombination
10
Virus Controls in shellfish
12
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
Food safety challenges: Controlling Foodborne Viruses. Dublin Dec1st 2015
NoV detection in shellfish ISO/TS 15216-1: 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 Food safety challenges: Controlling Foodborne Viruses. Dublin Dec1st 2015
Food safety challenges: Controlling
Foodborne Viruses. Dublin Dec1st 2015
14
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2g of digestive glands, add equal
vol. of proteinase K, 37°C and
60 and centrifuge
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Norovirus Controls-European Context
15
EFSA scientific opinion on Norovirus in oysters:
methods, limits and control options 2012
www.efsa.europa.eu/en/efsajournal
“….risk 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)
NoV detection by PCR–what does it mean?
16
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. 2012 Aug; 78(16):5812-7
This makes setting a standard (acceptable limit) for NoV in oysters difficult
Impact on industry vs public health benefit
Food safety challenges: Controlling Foodborne Viruses. Dublin Dec1st 2015
17
Cost
(indust
ry im
pac
t)
Benefit
(food s
afety
)
Calculating the balance
Benefit (difficult) Cost (relatively easy)
Dose Response NoV concentration in oysters
Outbreak data European baseline survey
EU wide Baseline Study
18
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
Food safety challenges: Controlling Foodborne Viruses. Dublin Dec1st 2015
Survey of Market Ready Oysters
19
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
Food safety challenges: Controlling Foodborne Viruses. Dublin Dec1st 2015
NoV (GI & GII) concentration in market ready oysters
20
203 348 150 1548 120
Overall Percentage detection rates (n=114)
Not detected Positive >200 >500 >1000
61.5 38.5 22.0 7.9 5.3
Food safety challenges: Controlling Foodborne Viruses. Dublin Dec1st 2015
21
Cost
(indust
ry im
pac
t)
Benefit
(food s
afety
)
Calculating the balance
Benefit (difficult) Cost (relatively easy)
Dose Response NoV concentration in oysters
Outbreak data European baseline survey
Dose response (published information)
22
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?
Food safety challenges: Controlling Foodborne Viruses. Dublin Dec1st 2015
Outbreak Information
Date No. ill NoV Levels (GI+GII) Comments
Feb
2010
>70 Restaurants 2,350 & 2040 A number of illnesses clusters in
Ireland and UK Harvest area 2,890 &1,920
Jan
2012
18 Restaurant 2,380 Dublin Restaurant
Harvest area 4,000
Feb
2012
20 Restaurant 1,446- 4,413 Illness in Denmark
Restaurant results from Danish NRL.
RASSF Harvest area 1,074
Nov
2012
<10 Restaurant 433 Galway Restaurant.
Dredged Oysters Harvest area 926; 2,775
23 Food safety challenges: Controlling Foodborne Viruses. Dublin Dec1st 2015
24
0
500
1000
1500
2000
2500
3000
3500
4000
NoV copies g-1
Sample (n=162)
NoV (GI & GII) Concentration in Market Ready
Oysters and Oysters Associated with Outbreaks
• Threshold of infection
remains undetermined
• Dose response –Increasing
concentration of NoV =
increasing risk of apparent
infection (outbreaks)
Food safety challenges: Controlling Foodborne Viruses. Dublin Dec1st 2015
FIRM Funded Project
NORORISK -developing a risk
assessment framework for NoV in Irish oyster areas
25
Risk Assessment Project
26
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
Food safety challenges: Controlling Foodborne Viruses. Dublin Dec1st 2015
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 0
500
1000
1500
2000
2500
3000
3500
4000
0 10 20 30
0
100
200
300
400
500
600
700
800
900
1000
0 10 20 30
0
50
100
150
200
250
300
350
400
0 10 20 30
Concentration of NoV GII per g in individual shellfish
Mean=88.2
Range=0-355
Mean=328.8
Range=89-892
Mean=1248.6
Range =220-3741
Food safety challenges: Controlling Foodborne Viruses. Dublin Dec1st 2015
Consumer Exposure
Oysters
eaten
Copies/g = 85 Copies/g = 325 Copies/g = 1250
2 146
(0 - 428)
598
(238 - 1138)
2516
(855 - 4821)
4 293
(47 - 661)
1196
(627 - 1941)
5062
(2521 - 8184)
6 442
(130 - 885)
1794
(1076 - 2712)
7605
(4374 – 11341)
8 589
(214 - 1089)
2388
(1544 - 3430)
10116
(6362 - 14422)
10 734
(308 - 1273)
2988
(2057 - 4121)
12612
(8417 - 17466)
95% interval for Norovirus genome copies consumed per meal size
Food safety challenges: Controlling Foodborne Viruses. Dublin Dec1st 2015 29
30
Drivers for NoV standards in shellfish
Food Safety (regulation)
outbreaks
EFSA opinion
DG Sanco
WG
Food safety challenges: Controlling Foodborne Viruses. Dublin Dec1st 2015
31
Drivers for NoV standards in shellfish
Food Safety (regulation)
outbreaks
EFSA opinion
DG Sanco
WG
Business
outbreaks
retailers
importing countries
Food safety challenges: Controlling Foodborne Viruses. Dublin Dec1st 2015
Risk Management
32
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?
Food safety challenges: Controlling Foodborne Viruses. Dublin Dec1st 2015
Dep.Area 2Area 1
5000
4000
3000
2000
1000
0
Ge
no
me
co
ncn
etra
tio
ns p
er g
Boxplot of of NoV concentrations in oysters
33 Food safety challenges: Controlling Foodborne Viruses. Dublin Dec1st 2015
Viruses & Shellfish –Summary (1)
34
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 15216-1)
Robust and reliable method to quantify NoV in oysters (and other foods)
does not distinguish between non-infectious and infectious virus particles
Food safety challenges: Controlling Foodborne Viruses. Dublin Dec1st 2015
Viruses & Shellfish –Summary (2)
35
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
Food safety challenges: Controlling Foodborne Viruses. Dublin Dec1st 2015