E.Coli bacteria may be able to travel further than was previously thought on the wind.

Research from the United States suggests that E.Coli bacteria – a common cause of food poisoning, some strains of which can be incredibly dangerous – can travel hundreds of meters downwind from cattle feedlots. The scientists studying disease spread suggested that the spread between livestock operations and horticulture, which has caused several bouts of sickness in the USA in recent years, may well be airborne.

Based on their findings, the researchers from the US Department of Agriculture warned that fresh produce planted up to almost 200 meters downwind of a feedlot could be at risk. They said, "The high percentages of leafy greens contaminated with E. coli suggest great risk for planting fresh produce 180 m [590 feet] or less from a feedlot."

Current US guidelines state that fresh produce should be grown 120 meters from a feedlot, but USDA scientist Elaine Berry from the Department's Agricultural Research Service centre in Nebraska said these may be inadequate.

In the study, investigators sampled leafy greens growing in nine plots, at distances of 60, 120, and 180 meters downwind from the cattle feedlot at the research centre over a two year period. The rate of contamination with the E.Coli declined fairly steeply with distance from the feedlot, where manure was sampled for the bacteria several times each year.  

USDA's Berry said a variety of conditions can affect the level of contamination. For example, following a period of high cattle management activity when the feedlot was dry and dusty, including removal of around 300 head of cattle for shipping, the rate of total non-pathogenic E. coli-contaminated leafy green samples per plot at 180 metres from the cattle shot up to 92.2 percent. High temperatures and dry weather were associated with greater contamination of crops downwind.

Conversely, total E. coli-positive leafy green samples were notably lower on one August sample date than on any other date, a finding the investigators attribute to cleaning and removal of feedlot surface manure from the nearby pens a few weeks earlier.

The investigators also found E. coli in air samples at 180 meters from the feedlot, though the instruments used were not sensitive enough to pick up the strain of E. coli being investigated (O157:H7). However, Berry said the bacteria's presence in air samples shows it could also be transmitted in this way.

Though Berry acknowledged that the research was conducted in Nebraska – which is not a produce growing state – the study author did state that the location was a reasonable model for some of the U.S.'s major produce growing regions, such as California's Central Coast, as winds there can blow almost as hard as in Nebraska, and both places can have dry summers, which can lead to to airborne transport of bacteria.