The Development of a Quantitative Microbial Risk Assessment Modelto Evaluate the Efficacy of Produce Rule Interventions to Reduce Norovirus and Hepatitis A Virus Contamination of Fresh Produce on Farms and Packing Facilities Pubblico
Marsh, Zachary (2016)
Abstract
From 1998 to 2008 in the United States, over 100,000 foodborne illnesses, 1,000 hospitalizations, and 13 deaths were attributed to norovirus (NoV) and hepatitis A virus (HAV). To mitigate the impact of foodborne pathogens like NoV and HAV and grant regulatory authority over intervention implementation, the United States Food and Drug Administration enacted the Food Safety and Modernization Act and established a set of minimum food safety interventions in the Produce Rule. The goal of this study was to evaluate the effectiveness of Produce Rule interventions at reducing the consumer NoV and HAV risk of infection (hereafter referred to as risk of infection) for four produce commodities in the pre-harvest, harvest, and packing stages of produce production. To achieve this goal, quantitative microbial risk assessment (QMRA) models were developed to estimate and evaluate the NoV and HAV risks of infection before and after the implementation of Produce Rule interventions. The QMRA models were designed to follow a produce item through a number of harvest and packing stages on US farms and packing facilities. The parameter estimates and distributions used to populate the model equations were obtained from publicly available literature data. For all produce commodities and scenarios, the QMRA models demonstrated the average NoV (8.28 x 10-2) risk of infection was significantly higher (p < 0.001) than that of HAV (5.81 x 10-7). There was a general trend observed that shorter harvest and packing operations and machine harvesting, instead of hand harvesting, resulted in lower risks of infection. Finally, it was found that all Produce Rule interventions reduced NoV and HAV risk of infection (range: 0.1- 70.0%), yet the magnitude of risk reduction was greatest for glove use (range: 36.4- 70.0%) and handwashing (range: 17.2- 40.3%). The NoV and HAV QMRA models were successful in demonstrating the ability of Produce Rule interventions to reduce NoV and HAV risk of infection on farms and packing facilities. This QMRA modeling approach could be used to identify and evaluate current and future food safety interventions on farms and packing facilities to ensure the United States maintains a safe and reliable produce production system.
Table of Contents
DISTRIBUTION AGREEMENT I
APPROVAL SHEET II
ABSTRACT COVER PAGE III
ABSTRACT IV
THESIS COVER PAGE V
LITERATURE REVIEW 1
STATEMENT OF CONTRIBUTION 15
INTRODUCTION 16
METHODS 19
MODEL OVERVIEW 19
PARAMETER ESTIMATES AND ASSUMPTIONS 20
MODEL EXECUTION 21
SENSITIVITY ANALYSIS 22
INTERVENTION ASSESSMENT 23
RESULTS 25
VIRAL RISK OF INFECTION 25
VIRAL CONTAMINATION 27
SENSITIVITY ANALYSIS 28
INTERVENTION ASSESSMENT 28
DISCUSSION 31
REFERENCES 37
TABLES 47
FIGURES 51
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