WASHINGTON – The U.S. Food and Drug Administration (F.D.A.) is investigating a possible link between a concentrated animal feeding operation (CAFO) and a canal used to irrigate romaine lettuce crops in Yuma, Ariz., associated with a multistate outbreak of E. coli O157:H7 illnesses.

The F.D.A. shared investigators’ preliminary hypotheses in a meeting of the Leafy Greens Food Safety Task Force that was formed in response to the outbreak.

The agency previously stated that samples of canal water tested positive for the outbreak strain of E. coli.

“The F.D.A. notes that the canal is close to a Concentrated Animal Feeding Operation, a facility with a large number of cattle on the premises,” the F.D.A. said in an update of the agency’s food safety investigation. “The CAFO can hold in excess of 100,000 head of cattle at any one time, and the F.D.A. traceback information showed a clustering of romaine lettuce farms nearby.”

Now, the F.D.A. is investigating whether the contaminated water came into contact with produce via direct irrigation or other means.

Additional strains of E. coli were found in water and soil samples, the agency added, but the samples from the canal water are the only matches to the outbreak strain.

As of June 27, the Atlanta-based Centers for Disease Control and Prevention (C.D.C.) have confirmed 210 individuals in 36 states became ill in the outbreak. Five people died, and 96 individuals were hospitalized.

“The traceback investigation indicates that the illnesses associated with this outbreak cannot be explained by a single grower, harvester, processor, or distributor," the F.D.A. said. "While traceback continues, the F.D.A. will focus on trying to identify factors that contributed to contamination of romaine across multiple supply chains.” 

Experts with the F.D.A. will continue examining potential links between the CAFO, nearby water sources and other factors that may explain the contamination and its relationship to the outbreak. The F.D.A. will release detailed findings in a final environmental assessment report.

“We urge other government and non-government entities, produce growers in the region and those engaged in managing the canal systems to work with the F.D.A. and marshal and deploy resources to achieve our collective food safety goal,” the F.D.A. said. “Broad engagement from the surrounding community is critical to developing and implementing remediation measures to reduce the potential for another outbreak. We believe local in-depth knowledge and actions are critical in helping resolve this issue in order to protect public health.”