Nearby cattle caused E. coli bacteria to enter an irrigation canal serving the whole Yuma region—farmers are trying to stop that from happening again.
Credit: Getty: Monty Rakusen

It's been more than four months since the United States' worst E.coli outbreak in over a decade, causing more than 200 people to fall ill in 25 states and five deaths. But the fact that federal agencies had such a hard time nailing down exactly where the outbreak began turned a health scare into full-blown hysteria: Romaine lettuce was stripped from shelves across the nation, tossed from kitchens, and shoppers were warned to stop all salad consumption until those at the Centers for Disease Control and Prevention could identify what caused the widespread outbreak.

It wasn't until the end of June that the Food and Drug Administration presented the theory that nearby cattle had caused the E. coli contamination from an irrigation canal in Yuma, Arizona—an explanation that sources say still isn't ironclad.

Now the farming community in Yuma—one of the nation's most significant sources of produce, especially lettuce—is taking extra steps to ensure future crops of romaine won't be affected this year.

Nearly all of the lettuce harvested in the U.S. comes from the Salinas Valley in California during the spring and summer months—but in the fall and winter, Yuma is largely responsible for the lettuce shoppers find in stores. The season for harvesting, and for business, is around the corner, so Yuma farmers have been discussing plans to deal with local water issues—including watering their crops with chlorine-treated water.

Farmers could even lobby together to purchase the nearby land that cattle are feeding on, currently known as Five Rivers Cattle Feeding, and shut them down as a precaution, according to a new NPR report. NPR's Dan Charles reports that farmers in the region have moved their lettuce crops into fields further away from the area's main source of water—all to convince buyers that another outbreak won't happen again, despite cattle still being in the area.

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FDA investigators were able to trace the same strain of E. coli linked to the outbreak in a canal that carries water to many different farms in the area, and NPR reports that more than 100,000 cows graze in an area adjacent to the canal. Federal experts suggested that the cow's manure, a prime source of E. coli bacteria, washed into the canal before that water was used to tend to romaine lettuce crops.

Credit: Victor Protasio

Other experts believe that water may have nothing to do with it—as irrigation water doesn't often come into contact with the lettuce leaves, and there were other crops of lettuce and vegetables growing in the area that weren't affected. Channah Rock, a water quality specialist at the University of Arizona, believes that contaminated dust from the cattle's lot blew onto romaine leaves.

Rock told NPR that the early crop of romaine, the cause of the outbreak, was affected by low temperatures, leaving "blistered" leaves vulnerable to E. coli contamination.

In any scenario, however, Yuma's farmers are holding cows responsible for the outbreak. The spillover effect from the romaine-lettuce-fueled E. coli outbreak is that shoppers are keeping a closer eye on federal agencies who are responsible for their safety—and as more and more foodborne illnesses are associated with fresh produce, farmers have a lot to prove this season.