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Overview of 3 published risk assessments

Don Schaffner, Ph.D.

Rutgers, The State University of NJ

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Three risk assessments

- Salmonella Enteritidis Risk Assessment

- Draft Risk Assessment of the Public Health Impact of Escherichia coli O156:H7 in Ground Beef

- Quantitative Assessment of Relative Risk to Public Health from Foodborne Listeria monocytogenes Among Selected Categories of Ready-to-Eat Foods

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Se in eggs

- Oldest “full” microbial risk assessment (started 1996, completed in 1998)

- Quite complex!

- Uses @risk add-in to Microsoft Excel

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Se in eggs objectives- Model from farm to table the unmitigated risk of

foodborne illness due to SE from the consumption of eggs and egg products;

- Identify target areas along the farm-to-table continuum for potential risk reduction activities

- Compare the public health benefits accruing from the mitigated risk of SE foodborne illness with the implementation of various intervention strategies

- Provide information on risk-effectiveness of mitigation to be utilized by the agency for subsequent cost-effectiveness and cost-benefit analysis

- Identify data gaps and guide future research and data collection efforts

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Diagram of Se in eggs QRA

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Diagrams from

production module

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Diagram (again)

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Shell Eggs Processing and Distribution Module

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Yolk membrane breakdown

- SE are found in the white

- The white contains growth inhibitors

- The yolk membrane keeps SE out of the yolk

- The yolk membrane degrades with time and temperature

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Data used to create model

Temperature (C)

10 15 20 25 30 35 40

Tim

e (d

ays)

0

10

20

30

40

50- Unpublished data from Tom Humphreys, UK

- Data points represent the time for more than 25% of a group of 9-11 eggs to permit SE growth

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Diagram of Se in eggs QRA

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Example of LE processing complexity

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Diagram of Se in eggs QRA

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Preparation and

consumption diagram

- Pooling (the process of combining eggs together) influences risk

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Diagram of Se in eggs QRA

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Dose response

Salmonella species used in feeding trials appear to be less virulent than SE, based on the epidemiologic data. Morales et al. (1996) proposed Shigella dysenteriae as a surrogate for SE

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E. coli O157:H7

- Initiated in 1998• http://www.fsis.usda.gov/OPHS/ecolrisk/

home.htm

- Draft released in 2001• http://www.fsis.usda.gov/OPPDE/rdad/

FRPubs/00-023NReport.pdf

- Reviewed by National Academy of Science 2002• http://books.nap.edu/books/0309086272/

html

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E. coli O157:H7 in ground beef objectives

- Goal is to produce a baseline risk assessment that • Reflects current practices along the farm-to-table continuum• Accurately assesses the likelihood of illness and death

- The primary use is to assist FSIS in reviewing and refining its risk reduction strategy for E. coli O157:H7 in ground beef

- The risk assessment produces scientific support for • Development of regulatory impact assessments to support FSIS

rulemaking• Identification of critical control points and critical control limits in

HACCP systems for ground beef • Risk-based sampling plans for FSIS inspectors• Identification of food safety research on E. coli O157:H7 in ground

beef.

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E. coli O157:H7 in ground beef diagram

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The problem of prevalence

- How common is the problem in herds?

- In a positive herd, how common is the problem?

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Why is season important?

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E. coli O157:H7 in ground beef diagram

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Slaughter module

Note that contamination may increase, decrease or stay the same

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E. coli O157:H7 in ground beef diagram

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Preparation module

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Change during storage

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Change during cooking

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E. coli O157:H7 in ground beef diagram

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Dealing with dose response

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Risk characterization (picture)

Log Number of E. coli per serving

-1 0 1 2 3 4 5 6 7 8 9 10 11 12

Log

num

ber

of s

ervi

ngs

-12

-11

-10

-9

-8

-7

-6

-5

-4-3

Ris

k of

illn

ess

0

20x10-9

40x10-9

60x10-9

80x10-9

100x10-9

120x10-9

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Risk characterization (words)

- Most contaminated cooked ground beef servings contain only 1 E. coli O157:H7 organism… and the risk of illness from one E. coli O157:H7 is low.

- Few contaminated cooked ground beef servings contain 100,000 E. coli O157:H7 organisms per serving (1.8 × 10-7) but this dose results in the highest risk of illness (1.0 × 10-7) from E. coli O157:H7 in a ground beef serving.

- Reducing the number of E. coli O157:H7-contaminated ground beef servings may reduce risk of illness more than reducing the amount of E. coli O157:H7 in contaminated servings.

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Listeria monocytogenes in RTE foods

- The purpose of the assessment is • to examine systematically the available scientific data and

information• to estimate the relative risks of serious illness and death associated

with consumption of different types of ready-to-eat (RTE) foods

- This examination of the current science and the models developed from it are among the tools that food safety regulatory agencies will consider when evaluating the effectiveness of current and future policies, programs, and regulatory practices.

- A distinction is made between the mild non-invasive illness (referred to as listerial gastroenteritis) and the severe, sometimes life-threatening, disease (referred to as listeriosis). This risk assessment only considers listeriosis.

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Listeria monocytogenes in RTE foods

- Released plan in 1999

- Released draft in 2001

- Revised in 2003

- Note different FAO/WHO risk assessment ongoing during the same time

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What does it do?

- Provides analyses and models that…• Estimate the potential level of exposure

• Three age-based population groups and the total United States population to

• Listeria monocytogenes contaminated foods for 23 food categories

• Relates this exposure to public health consequences

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Diagram of QRA

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Interesting features

Assumed detected Lm is just the tip of the iceberg

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Comparing relative ranks

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Risk Characterization

- High risk per serving• Deli Meats• Frankfurters, not

reheated• Pâté and Meat

Spreads• Unpasteurized Fluid

Milk• Smoked Seafood• Cooked Ready-to-Eat

Crustaceans

- High risk per year (cases)• Deli Meats (1598.7)• Pasteurized Fluid Milk

(90.8)• High Fat and Other

Dairy Products (56.4)• Frankfurters, not

reheated (30.5)

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RC table

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Three very different risk assessments

- Salmonella Enteritidis in eggs• Farm-to-fork, many foods

- Draft Risk Assessment of the Public Health Impact of Escherichia coli O156:H7 in Ground Beef• Farm-to-fork, single food, still not done!

- Quantitative Assessment of Relative Risk to Public Health from Foodborne Listeria monocytogenes Among Selected Categories of Ready-to-Eat Foods• Limited scope (i.e. not farm-to-fork), many (many!)

foods