New Research into Causes of E.coli Contamination in Romaine

With multiple outbreaks linked to E.coli contamination in the past couple of years, romaine lettuce remains a hot topic among food safety experts and researchers searching for answers as to how these outbreaks began. One group of experts has captured and studied whether or not flies can spread E.coli from cattle ranches to fields used for leafy greens.

E. coli contamination
Image credit: DavidCardinez via Pixabay

Past reports have suggested contaminated water supplies or contaminated equipment spread the E.coli from one field to another, but this new research concerning flies has us wondering if there may be an uncontrollable aspect to the spread of bacteria on farms.

Flies and E.coli Contamination on Farms

Before we go any further, it’s important to note that the official research abstract does not in fact link flies to recent E.coli contamination outbreaks, it simply examines the plausibility that flies can transmit the bacteria.

The studies were conducted on fields in Yuma, AZ, near or adjacent to feedlots which can house up to 100,000 cattle at once. Weather trends also show that winds regularly blow through the feedlots and towards fields used to grow leafy greens such as romaine lettuce. These patterns do show that the same flies that feed on manure in the cattle yard are highly capable of visiting both the cattle yards and growing fields in a short amount of time, but can these flies actually be the agent that began a major outbreak?

In order to determine whether flies can be transmitters of E.coli, researchers collected samples of five different varieties of flies in the growing fields and cattle feedlots:

  • House Flies
  • Face Flies
  • Flesh Flies
  • Blow Flies
  • Stable Flies

In samples collected, four out of five species carried E.coli at nearly the same rate, with stable flies still testing positive, but at lower levels. It was also discovered that the rates of flies that carried the E.coli bacteria on feedlots were the same up to 180 meters away from cattle.

While researchers admit that further study is required to determine how much of an impact flies have had on romaine E.coli contamination outbreaks and how much distance should exist between cattle raising areas and leafy green growing fields, it’s interesting to note that potential causes for these outbreaks are more varied than previously thought.

We love coming across studies like this examining alternative causes of food safety hazards. Do you think the food safety protection agencies are doing enough to examining potential causes of E.coli poisoning outbreaks?

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