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July 19, 2005
A notice of availability of the Food and Drug Administration (FDA) draft risk assessment on the relationship between Vibrio parahaemolyticus in raw molluscan shellfish and public heath was published in the Federal Register of January 19, 2001 (66 FR 5517). A comment period was established during which FDA actively sought comments, suggestions, and additional data sources. The results of the draft risk assessment were presented for clarification during a public meeting on March 20, 2001 (66 FR 13544). Comments were submitted to the FDA Docket (No. 99N-1075) from nine institutions or individuals. The data and information acquired during the comment period were reviewed and used, as appropriate, to further enhance the risk assessment.
We appreciate the time and effort expended to submit these comments, and have addressed these in this revised risk assessment to the best of our ability. A summary of the modifications made to the draft risk assessment in response to the comments, new data and modeling techniques is provided below. A more detailed discussion of our response to the public comments can be found in Appendix 2.
Modifications Made to the 2001 Draft Vibrio parahaemolyticus Risk Assessment
Topic | Modifications |
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Assumptions |
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Additional Data/ Information |
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Modeling techniques |
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Team Leader: | Marianne Miliotis |
Project Manager: | Marianne Miliotis |
Risk Analysis Coordinator: | Sherri Dennis |
Scientific Advisor: | Robert Buchanan |
Team Members
Modeling:
Exposure Assessment:
Hazard Characterization:
Epidemiology:
Technical Editing:
The Vibrio parahaemolyticus Risk Assessment team greatly appreciates the efforts of the following individuals who provided us with comments, information and assistance for this risk assessment:
We are also deeply grateful to Sharon Edelson Mammel for evaluating the quality of data used in the model and to Louis Michael Thomas, Linda Shasti, and Aesha Minter, JIFSAN student interns, for assembling the references cited in the document. We also thank CDC staff for their assistance in providing the epidemiological data used for the dose-response model and the data analysis used to compare the model predictions to the epidemiological data. Our appreciation also goes to David Acheson (FDA), Robert Buchanan (FDA), Don Kraemer (FDA), Angela Ruple (NOAA Fisheries), and Richard Whiting (FDA) for reviewing and providing suggestions to improve the risk assessment documents. The team is also appreciative of the in depth review and evaluation of the model conducted by Clark Carrington (FDA) and Darrel Donahue (University of Maine).
The Vibrio parahaemolyticus risk assessment team members:
Team Leaders: Marianne Miliotis and William Watkins
Exposure Assessment - Harvest Module:
Marleen Wekell (Section Lead), Atin Datta, Elisa Elliot, Walter Hill, Charles
Kaysner, Brett Podoski
Exposure Assessment - Post-Harvest Module:
Angelo DePaola and David Cook (Section Co-leads), George Hoskin, Susan McCarthy,
William Watkins
Exposure Assessment - Consumption Module:
Michael DiNovi
Epidemiology:
Marianne Ross (Section Lead), Karl Klontz, Debra Street, Babgaleh
Timbo
Hazard Characterization/Dose-Response:
Donald Burr (Section Lead), John Bowers, Mahendra Kothary, Wesley
Long, Marianne Miliotis, Ben Tall, Mark Walderhaug
Modeling:
John Bowers (Section Lead), Mark Walderhaug
The following people provided the V. parahaemolyticus team with comments, information and assistance we needed to accomplish this risk assessment:
The team would especially like to thank the FDA/CFSAN Offices and Risk Assessment Consortium members for intensive review of the document in December, as well as Federal employees from other agencies, and Special Government Experts, for review of the document in May. We are also deeply grateful to Lauren Posnick for her outstanding contribution in preparing the interpretive summary of this document, Carolyn Jeletic for excellent technical editing of this document, and Faye Feldstein for assisting with assembling all the references.
Term | Definition |
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Case series | Study of cases of similar illness occurring over a period of time. |
Compliance | Voluntarily choosing to follow the guidelines |
Depuration | The process of reducing pathogenic organisms that may be present in shellfish using a controlled aquatic environment, such as land-based tanks, as the treatment process. |
Dose | The number of pathogenic V. parahaemolyticus consumed in oysters at one sitting. |
Dose-response | The relationship of the levels of V. parahaemolyticus ingested with the frequency and magnitude of illness. |
Gastroenteritis | Inflammation of the gastrointestinal tract; symptoms typically include diarrhea, vomiting, and/or abdominal cramps, caused by an infecting organism which is present in feces. |
Gyrase B | A prokaryotic gene which codes for the enzyme gyrase that unwinds DNA so it can be replicated. |
Imputation (impute) | The statistical practice of substituting missing data with plausible values. For example, in regard to samples with densities less then the sensitivity of an enumeration method (e.g., <0.3 cfu/g) plausible values in the range between zero and 0.3 may be imputed using statistical methods. |
Isolate | A single colony identified from a mixed bacterial culture on an agar plate |
Iteration | A single calculation of model output(s) based on a set of sampled variability and/or uncertainty model inputs (factors). |
Kanagawa phenomenon | Hemolysis induced by the thermostable direct haemolysin on a special blood agar, Wagatsma medium. |
Maximum likelihood estimate (MLE) | An estimate (e.g., of a model parameter) such that the observed outcome is the most likely of all possible outcomes. |
Midday temperature | Temperature taken at noon. |
Mode | A statistical term; most likely value. |
Monte-Carlo Simulation | Computer experiments of modeled relationships that simulate probabilistic variation using random numbers generated by specified distribution functions. |
Outbreak | The occurrence of similar illness involving 2 or more persons resulting from the ingestion of a common food. |
Pathogenic V. parahaemolyticus | For the purpose of this risk assessment, pathogenic V. parahaemolyticus strains are those that produce thermostable direct hemolysin (TDH) and/or hemolyse red blood cells on a blood agar plate, which is referred to as the Kanagawa Phenomenon -positive (KP-+ve). |
Relaying | The process of reducing pathogenic organisms or deleterious substances that may be present in shellfish by transferring shellfish from a contaminated growing area to one that is not. |
Sensitive subpopulation | Group of people with greater vulnerability to more severe V. parahaemolyticus disease (i.e., septicemia) as a result of some underlying state of compromised health, such as liver disease, blood disorder, or immunodeficiency. |
Septicemia | A systemic disease caused by the multiplication of pathogenic microorganisms and/or the presence and persistence of their toxins in the circulating blood. |
Skow | A flat bottomed, flat decked "barge" towed by another boat; some may be motorized, have a cabin, and a boom hoist. |
Species | Bacterial collections of similar strains. |
Sporadic case | When a single individual becomes ill; an isolated event not documented as occurring in the context of an outbreak. |
Strain | A group of organisms of the same species, having distinctive characteristics but not usually considered a separate breed or variety. |
Thermocouple | A device for measuring temperature. A pair of wires of dissimilar metals are joined and the free ends of the wires are connected to an instrument (as a voltmeter) that measures the difference in potential created at the junction of the two metals. |
Thermostable direct hemolysin | A toxin produced by V. parahaemolyticus that lyses red blood cells in Wagatsuma agar. |
Thermostable-related hemolysin | A toxin very similar in action and characteristics to, but genetically distinct from the thermostable direct hemolysin. |
Tobit regression | A type of regression model, applicable to limit-of-detection truncated or censored data, whereby unbiased parameter estimates are obtained without the need for imputation in place of missing values |
Total V. parahaemolyticus | The summation of pathogenic (tdh+) and non-pathogenic (tdh-) V. parahaemolyticus cells in a specified unit of volume or mass. |
Uncertainty | An expression of the lack of knowledge, usually expressed as a probability distribution; pertaining to the lack of knowledge concerning a fixed but unknown quantity. |
Uncertainty Distribution | A description of the range of plausible values for a prediction. |
Variability | A description of differences of an attribute among the individual members of a series or population. |
Virulence | The capacity of a microbial pathogen to invade and/or produce illness in the host. Mediated by the presence of specific genes and their protein products that interact with the host. |
Water activity | The ratio of the water vapor pressure in any kind of food system to the water vapor pressure of pure water; aw = P product / Pwater. |
Acronym/ Abbreviation | Definition |
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CDC | Centers for Disease Control and Prevention |
CFSAN | Center for Food Safety and Applied Nutrition |
FAO | Food and Agricultural Organization of the United Nations |
FDA | Food and Drug Administration |
GCSL | FDA Gulf Coast Seafood Laboratory, Dauphin Island |
GCVSS | Gulf Coast Vibrio Surveillance System |
IAFP | International Association for Food Protection |
ICP | ISSC Interim Control Plan for monitoring levels of pathogenic V. parahaemolyticus in oysters at time of harvest |
ISSC | Interstate Shellfish Sanitation Conference |
MSI | Molluscan Shellfish Industry |
NACMCF | National Advisory Committee on Microbiological Criteria for Foods |
NCTR | National Center for Toxicological Research |
NERR | National Estuarine Research Reserve System |
NBDC | National Buoy Data Center |
NOAA | National Oceanic and Atmospheric Administration |
NOS | National Ocean Services |
NSSP | National Shellfish Sanitation Program |
NWS | National Weather Service |
PCSGA | Pacific Coast Shellfish Growers Association |
RAC | Interagency Risk Assessment Consortium |
SGE | Special Government Employee |
STORET | EPA Storage and Retrieval of U.S. Waterways Parametric Data database |
WHO | World Health Organization |
Bp | base pairs |
C | Celsius |
CFU | Colony Forming Units |
DIG | digoxygenin |
F | Fahrenheit |
/g | per gram |
g | grams |
gyrB | gyrase B |
HGMF | Hydrophobic Grid Membrane Filtration procedure |
h | hours |
ID50 | Infective Dose at which 50% of infected subjects become ill |
KP+ | Kanagawa-positive |
LD50 | Lethal Dose at which 50% of infected subjects die |
LOD | Limit Of Detection |
Mb | mega base pairs |
min | minute |
ml | milliliters |
MLE | Maximum likelihood estimates |
MPa | Mega Pascals |
MPN | Most Probable Number |
PBS | phosphate buffered saline |
ppt | parts per thousand |
RITARD | removable intestinal tie adult rabbit diarrhea |
TDH | thermostable direct hemolysin |
TRH | thermostable-related hemolysin |
TTSS | Type III Secretion System |
VBNC | viable but not culturable |
Vp | Vibrio parahaemolyticus |
Vppath | pathogenic strains of V. parahaemolyticus |
Quantitative Risk Assessment on the Public Health Impact of Pathogenic Vibrio parahaemolyticus in Raw Oysters; Risk Assessment Federal Register Notice of Availability; July 20, 2005
Quantitative Risk Assessment on the Public Health Impact of Pathogenic Vibrio parahaemolyticus in Raw Oysters; Risk Assessment Federal Register Notice of Public Meeting; July 20, 2005