It is widely recommended that adults and children eat a variety of fruits and vegetables to round out a healthy and nutritious diet. However, leafy vegetable consumption poses a unique problem in that they are generally consumed raw, which increases the risk of transmitting foodborne illness. California is responsible for more than 75 percent of leafy greens grown in the U.S. From 1999-2008, the state produced leafy greens with a significant concentration of E. coli outbreaks from July to November. In order to understand the pathway of E. coli in leafy green production, University of Maryland researchers developed the first dynamic system model which simulates the effects of soil, irrigation, cattle, wild pig and rainfall in a hypothetical farm.
Results of the system model conclude that the peak July to November timeframe is consistent with the prevalence of E. coli in cattle and wild pig feces in the Salinas Valley, a major leafy greens producing region in California. The finding was the most evident after examining the results of various scenarios. From this, the research team concluded that the concentration of E. coli in leafy greens can be significantly reduced if feces contamination is controlled. By measuring the numerous factors associated with leafy green contamination in a farm setting, UMD’s College of Agriculture and Natural Resources offers a significant contribution to the science-based process of preventing leafy greens outbreaks in the future.
According to a 2015 study on leafy vegetable-associated outbreaks, leafy vegetables were linked to over 600 outbreaks in the U.S. from 1973-2012, causing more than 20,000 illnesses and 1,000 hospitalizations. Of the bacterial pathogens, E. coli was responsible for about 50 outbreaks, more than 1,600 illnesses, and 450 hospitalizations.
“Results of our study can help prevent crop contamination at the preharvest stage, reducing the number of leafy green related illnesses in the future,” said Abani K. Pradhan, Ph.D. of UMD’s College of Agriculture and Natural Resources. “We are excited that this research blends our team’s knowledge of food safety and computational microbiology, and allows us to estimate the impact of various sources of contamination which pose threats to our food supply and security.”
The findings have implications for future research. According to Pradhan, this model can be extended or adopted to examine other crops that are affected by harmful pathogens. In addition to E. coli, Pradhan’s team is currently exploring system models for tomatoes and cucumbers in the Mid-Atlantic region.
Pradhan and his team, in collaboration with a researcher from Rutgers University, completed a manuscript titled “A System Model for Understanding the Role of Animal Feces as a Route of Contamination of Leafy Greens before Harvest,” which was recently published in the journal Applied and Environmental Microbiology.
March 23, 2017