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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 O156H7 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 _at_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

• Unpublished data from Tom Humphreys, UK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 O157H7

• Initiated in 1998
• http//www.fsis.usda.gov/OPHS/ecolrisk/home.htm
• Draft released in 2001
• http//www.fsis.usda.gov/OPPDE/rdad/FRPubs/00-023N
  Report.pdf
• Reviewed by National Academy of Science 2002
• http//books.nap.edu/books/0309086272/html

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E. coli O157H7 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 O157H7 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
  O157H7 in ground beef.

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E. coli O157H7 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 O157H7 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 O157H7 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 O157H7 in ground beef diagram
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Dealing with dose response
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Risk characterization (picture)
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Risk characterization (words)

• Most contaminated cooked ground beef servings
  contain only 1 E. coli O157H7 organism and the
  risk of illness from one E. coli O157H7 is low.
• Few contaminated cooked ground beef servings
  contain 100,000 E. coli O157H7 organisms per
  serving (1.8 10-7) but this dose results in the
  highest risk of illness (1.0 10-7) from E. coli
  O157H7 in a ground beef serving.
• Reducing the number of E. coli O157H7-contaminate
  d ground beef servings may reduce risk of illness
  more than reducing the amount of E. coli O157H7
  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 O156H7 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