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Environmental Health Investigations: Conducting Traceback Investigations

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Environmental Health Investigations: Conducting Traceback Investigations Goals Describe the basic steps of conducting a traceback investigation Identify when it is ... – PowerPoint PPT presentation

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Title: Environmental Health Investigations: Conducting Traceback Investigations


1
Environmental Health InvestigationsConducting
Traceback Investigations
2
Goals
  • Describe the basic steps of conducting a
    traceback investigation
  • Identify when it is appropriate to conduct a
    traceback investigation
  • Provide examples of recent outbreak
    investigations that carried out traceback
    investigations

3
Quick reviewTraceback Investigations
  • Process used to determine the production and
    distribution chain of a vehicle implicated in an
    outbreak.
  • Helps determine if (and where) you can conduct an
    environmental health assessment
  • Used to clarify the point at which the implicated
    vehicle may have become contaminated

4
Traceback Investigations
  • Identify
  • Places where the implicated vehicle has been AND
  • If the vehicles to which different cases have
    been exposed had places in common
  • Identification of a common place strongly
    suggests contamination at/before that point in
    production or distribution of the vehicle

5
Traceback Investigations
  • Do not identify the source of the
    problem/contamination
  • Tell investigators where to look
  • Further investigation/inspection is necessary to
    identify contributing factors or implement
    control measures

6
Traceback Investigation Example 1
  • 1994 Nationwide outbreak of Salmonella
    Enteritidis associated with a particular brand of
    ice cream. (1)
  • Ice cream obtained by cases in 41 states from
    multiple warehouses across the country
  • BUT, all ice cream eaten by cases prepared in one
    plant in Minnesota

7
Traceback Investigation Example 1 (cont.)
  • Implicated plant obtained ice cream pre-mix
    shipped via truck from two suppliers
  • Identification of a common ice cream plant
    suggested contamination with S. Enteritidis
    occurred at or before that point in the
    production such as
  • Plant
  • Tanker trucks
  • Pre-mix suppliers
  • Follow-up assessments found problems with
    inadequate cleaning of tanker trucks that were
    also used to carry non-pasteurized eggs

8
Traceback Process
  • Begins with information from cases about the
    implicated vehicle
  • Extends backwards in time
  • All points in the production and use of the
    vehicle are considered
  • Retailers
  • Point of service establishments (e.g.
    restaurants)
  • Distributors
  • Importers
  • Producers

9
Vehicle Distribution Patterns
  • Distribution patterns may be complex
  • Retailers may obtain vehicle from more than one
    distributor, distributors may change over time
  • Distributors may have multiple sources, may
    supply to other distributors
  • Producers may be domestic or foreign

10
Traceback Investigation Example 2
  • 1997 E. coli 0157H7 outbreak in Michigan (2)
  • Case-control study revealed strong association
    with eating alfafa sprouts
  • Traceback investigation initiated by collecting
    data from cases
  • Places sprouts were purchased/eaten
  • Locations of said establishments
  • Dates of purchase/consumption

11
Traceback Investigation Example 2 (cont.)
  • Investigators used store and restaurant records
    to identify likely sprouting facilities for
    implicated sprouts
  • Source of sprouts traced for all 16 patients
  • Source Facility A for 15 patients
  • Source Facility B for 1 patient
  • Seed sources identified
  • Facility A 2 seed lots (Idaho Australia)
  • Facility B multiple seed lots

12
Traceback Investigation Example 2 (cont.)
  • Concurrent outbreak of E.coli O157H7 in
    Virginia, also tied to alfafa sprouts
  • Source of sprouts for 13 VA patients traced to a
    single sprouting facility in VA using seed lot
    from Idaho, same as in Facility A in Michigan
  • Facility B determined to have used Idaho seeds
    also, but only for 2 days
  • Conclusion problem resided in seeds from Idaho

13
Identification of Products
  • Clear identification of implicated products is
    essential to a traceback
  • Branded (commercial) products do not always
    provide clear identification
  • If package is not available, consumers may not
    remember exact name
  • One product may be repackaged and distributed
    under different names

14
Traceback Investigation Example 3
  • 1998 49 cases of Salmonella Agona reported in
    Illinois (3)
  • Nine other states also had increases in S. Agona
  • PFGE subtyping suggested cases had common origin
  • Matched case-control study linked S. Agona
    infections with consumption of cereal but no
    common brands were noted

15
Traceback Investigation Example 3 (cont.)
  • Traceback investigation revealed implicated
    cereal was produced by a Minnesota company,
    Malt-O-Meal
  • Cereal sold under brand name Toasty-Os
  • BUT also sold as Toasted Oats under in-house
    labels in 39 grocery stores
  • All cases had consumed a common cereal

16
Product Identification Is Not Enough
  • Most outbreaks are due to a temporary problem in
    production chain
  • Knowing a brand name is not enough, you also
    need
  • Item description
  • Place, date of purchase
  • Manufacturer, supplier and lot number
  • Locations of farms, production facilities,
    supplier information, delivery schedules

17
Getting Started
  • For a traceback investigation information is
    collected from
  • Cases
  • Retailers or point of service establishments
  • Distributors/importers
  • Producers/processors

18
Traceback First Steps
  • Begin with information available from interviews
    of the cases about the time and place of purchase
    of implicated item
  • Original packaging and labels with identifying
    features (lot numbers, names of manufacturers)
    are helpful

19
Traceback Next Steps
  • Continue investigation at place(s) where cases
    obtained items such as retail stores or
    restaurants
  • Expand investigation to distributors
  • Includes brokers and importers and may have
    multiple levels
  • Business documentation (invoices, inventory
    records, air bills, bills of lading) and customs
    forms can be helpful

20
Traceback Final Steps
  • A traceback investigation is completed when firms
    that supplied, processed and produced the
    implicated product are identified
  • Investigation may include a visit to the source
    to verify information collected (production
    dates, locations of farms/facilities)
  • Validity of a traceback investigation is highly
    dependent on proper documentation
  • Missing documentation (such as receipts or
    labels) makes the investigators job difficult

21
To Trace or Not to Trace?
  • Tracebacks can be time consuming
  • While important, such investigations should be
    undertaken selectively
  • Criteria for undertaking a traceback
  • Certainty that the vehicle in question is truly
    implicated in the outbreak AND that
  • The source of the contamination is within the
    production chain

22
To Trace or Not to Trace?
  • Other key questions to consider
  • Is there solid epidemiologic evidence linking the
    outbreak and the implicated products?
  • Is there historical precedent for the product
    being contaminated with the organism in question?
  • Is there microbiological evidence linking the
    outbreak and the implicated products?

23
To Trace or Not to Trace?
  • Key questions, continued
  • Does the vehicle have chemical and physical
    characteristics conducive to the survival and
    growth of the causative agent?
  • Has mishandling or environmental contamination of
    the product by the consumer, retailer or point of
    service establishment been ruled out?
  • Could the product be commercially distributed in
    a way that is consistent with the outbreak?

24
To Trace or Not to Trace?
  • Another factor to consider is the likelihood of
    success
  • Tracebacks are most successful with
  • Commercially packaged products (identifying
    label)
  • Unusual products (salami)
  • Products with a long shelf-life (frozen
    hamburger)
  • Traceback investigations are unproductive with
  • Products with a short shelf-life (fresh fruits
    and vegetables)
  • Products derived from multiple sources (blood
    clotting factor from multiple donors)

25
To Trace or Not to Trace?
  • Weigh benefits of the investigation
  • How serious is the disease?
  • Death, hospitalization or permanent disability?
  • Is exposure likely to be ongoing?
  • Are vulnerable populations at risk?
  • Infants, elderly, immunocompromised persons?
  • A yes to any/all of these questions might
    provide justification to undertake a traceback
    investigation

26
Success Factors
  • Coordination among many players
  • Local, state or federal agencies
  • Good solid epidemiological data
  • Poor epidemiologic studies might implicate the
    wrong vehicle and misdirect the investigation
  • Information obtained from epidemiological
    investigation about the vehicle is often the
    first step in the traceback investigation

27
Conclusion
  • To trace the source of an outbreak you need to
    look back in time
  • Use a traceback investigation as a first step in
    determining where problems may have occurred in
    the chain of production of an implicated vehicle
  • Traceback investigations provide data for the
    next step the environmental health assessment

28
References
  • 1. Hennessy TW, Hedberg CW, Slutsker L, et al. A
    national outbreak of Salmonella Enteritidis
    infections from ice cream. N Engl J Med.
    19963341281-1286.
  • 2. Breuer T, Benkel DH, Shapiro RL, et al. A
    multistate outbreak of Escherichia coli O157H57
    linked to alfalfa sprouts grown from contaminated
    seeds. Emerg Infect Dis. 20017977-982.
  • 3. CDC. Multistate outbreak of Salmonella
    Serotype Agona infections linked to Toasted Oats
    cerealUnited States, April-May, 1998. MMWR Morb
    Mortal Wkly Rep. 199847462-464.
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