P1-158 Evaluation of Different Animal Feces Levels on Contamination of Leafy Greens Using Sensitivity Analyses of a Mathematical System Model

Monday, July 10, 2017
Exhibit Hall (Tampa Convention Center)
Abhinav Mishra , University of Maryland , College Park , MD
Hao Pang , University of Maryland , College Park , MD
Robert Buchanan , University of Maryland, Department of Nutrition and Food Science and Center for Food Safety and Security Systems , College Park , MD
Donald W. Schaffner , Rutgers University , New Brunswick , NJ
Abani Pradhan , University of Maryland , College Park , MD
Introduction: During 1973-2012, Escherichia coli O157:H7 was associated with 46 outbreaks in leafy greens, causing 1,584 illnesses and 430 hospitalizations in the US. A large majority of the salad greens consumed in the US are grown within the Salinas region in California. This region has also been associated with the production of leafy greens implicated in several E. coli O157:H7.

Purpose: The objective of this study was to develop a system model that simulates the effect of animal feces as a source of contamination in leafy greens, and to conduct a sensitivity analyses to determine the impact of different levels of animal feces on contamination of leafy greens. 

Methods: A system model consisting of subsystems and inputs to the system (soil, irrigation, cattle, swine, and rainfall) simulating a hypothetical farm in the Salinas Valley was developed. For sensitivity analyses, the levels of contamination in the baseline model were increased and decreased by up to 100% at intervals of 20% (i.e., ±20%, ±40%, ±60%, ±80%, and ±100%). 

Results: At the level of a 100% increase in swine defecation, the mean value of E. coli in the harvested crops increased by 1.66- to 4.56-fold compared with the level in the baseline model. When swine defecation was decreased by 100%, the decrease in the mean values was in the range of 1.66- to 11.62-fold. Similarly, when the runoff was increased by 100%, the increase in the mean populations of E. coli in the crops was 1.45- to 7.17-fold. The mean population of E. coli in the crops was predicted to decrease by 2047- to 8822-fold during April to June and by 1.64- to 6.86-fold during July to November, when the runoff was decreased by 100%.

Significance:

These results could be useful in developing metrics to mitigate the risks of leafy greens associated outbreaks.