Vibrio vulnificus Calculator

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Vibrio vulnificus Calculator

• VMC/Gulf Regulators
• Conference Call
• August 1, 2008

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ISSC adopted Vv illness reduction plan1999?

• 60 illness reduction goal (per capita)
• Core states CA, TX, LA FL
• Baseline 1995-1999 21.4 cases/yr
• Education and increasing PHP capacity
• 7 year plan with reductions based on ave cases
  in 2007 2008

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Current Status

• 2007 cases19
• 24.8 reduction from baseline
• Adjusted for population increase
• 2008 partial cases3
• Plan does not reach goal if 20 or more cases
  occur in 2007 2008 combined
• Goal will not be met
• Goal shortfall cannot be determined until after
  2008

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Consequences of not achieving goal

• Seasonal closures (100 effective)
• Diversion to PHP (100 effective)
• Label for cooking only OK for Vv? (100
  effective)
• Other means?
• Time/temperature controls
• High salinity relaying
• ISSC Spring Executive Board Mtg
• Gulf States submit control plan by Aug. 15, 2008
  (amended?)
• States implement plans in 2010

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Time/Temperature Controls

• GSASSC New Orleans June 2008
• Gulf regulators requested that FDA develop risk
  calculator similar to that proposed for VPCP
• Vv Risk calculator
• Based on 2005 FAO/WHO VVRA
• Dose response based on reported cases in US

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Beta Poisson vs Exponential
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Vv Calculator Features

• Derived from FAO/WHO VVRA
• Monte Carlo simulations
• Time consuming
• Expensive software
• Trained operators
• Vv risk calculator
• Based on regression fits to a set of Monte Carlo
  simulation output
• Calculates Vv levels risk instantly
• Flexible to evaluate diverse scenarios and
  different end points for desired level of illness
  reduction

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Average monthly maximum water temperature (AMMWT)

• Determines Vv levels at harvest based on
  relationship between water temperature Vv level
  from Vv risk assessment (VVRA)
• State determines scale area, basin or entire
  state (buoy, sampling)
• Gulf-wide

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Effect of Temperature on Vv densities in Gulf
Coast oysters
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Average monthly air temperature

• Surrogate for oyster temperature
• Determines Vv growth rate
• Ave. air temperature determination
• Ave. monthly noon air temperature
• Ave. monthly maximum temperature
• Ave. monthly air temperature during harvest
  period (i.e. 6-11 AM)
• Ave. oyster temperature during harvest period

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Baseline max. time to refrigeration

• Controls that were in place during the baseline
  period of 1995-99
• Vary from state to state
• Alternatively 10h for summer month?
• Represents control used for most Gulf oyster
  harvest

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Baseline Max cool down time

• Time from when oysters are first placed into
  refrigeration until reach no growth temperature
  of 13C or 55F
• 10 hour is assumption used in both FDA VPRA and
  FAO/WHO VVRA
• Ave cool down between 1 to 10 hours

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Demonstration of using Vv risk calculator

• Baseline (1995-99) controls
• Effect of VPCP on Vv risk
• Risk at harvest (best case scenario)

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Calculator Inputs

• Average monthly water temperature
• Average monthly air temperature
• Maximum time to first refrigeration
• Maximum cool down time

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Calculator Outputs

• Vv levels at consumption
• Vv risk per 100,000 meals
• Number of cases per month (Nation wide)
• change in number of cases from the baseline

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Baseline Demonstration

• Open Excel
• Vv Calculator Tab

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Effect of VPCP on Vv Risk

• lt5h if gt81F Tab

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Vv Risk at Harvest

• Risk at Harvest Tab

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Caveats

• Dose response not linear does not provide
  outputs above 90F and gt15h to first refrigeration
• Controls changed in 1997 during baseline period
  (1995-99)
• Controls vary across Gulf states
• Implementation of VPCP in 2008
• Max. time to refrigeration
• Changes in volume of harvest for raw consumption?
• raw consumption varies across Gulf states

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Summary

• Scenario analysis
• Manage on monthly scale
• Modify time to refrigeration and cool down times
• Outputs
• Vv levels at consumption
• Vv risk per 100,000 meals (at risk population)
• Expected number of cases
• Change from baseline