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FDA Now Considers Cattle Feeding Operation Responsible for Contamination of Yuma, AZ. Lettuce


As reported widely in media, romaine lettuce was the vehicle of infection for at least 210 cases of E.coli O157:H7 (STEC) infection resulting in five fatalities and extending over 36 states. The outbreak was declared over on June 28th. This was mainly due to the fact that the harvest season in the Yuma Valley ceased a few weeks earlier and lettuce in the food chain had either been consumed or destroyed.

Concurrent with the declaration that the outbreak was over, the FDA isolated the outbreak pathogen from irrigation water sprayed on the fields. This revelation was months after the initial cases were detected and recognized as a discrete outbreak through the FoodNet database system.

The latest announcement implicates a large Concentrated Animal Feeding Operation (CAFO) located near the area where romaine lettuce was cultivated as the source of contaminated irrigation water. This should not come as a surprise since E.coli O157:H7 has adapted to the intestinal tract of ruminants, especially when fed diets low in roughage such as on zero-grazing dairy farms and feed lots. Previous outbreaks of STEC infection attributed to cattle include an outbreak with spinach as the vehicle of infection during 2006 in California. Aerosolized fecal material from cattle wafting into apple orchards was responsible for an extensive outbreak of E.coli O157 in children consuming non-pasteurized apple juice in 1999. Ground beef derived from culled dairy cattle may be contaminated with E.coli O157 requiring thorough cooking to inactivate the pathogen.

The FDA is continuing to investigate the outbreak. The slow pace of the study and failure to identify the epidemiologic factors relates to the lack of suitably trained investigators affiliated to the FDA. The Centers for Disease Control and Prevention is a suitably equipped agency to determine the source of food-borne disease outbreaks given their resources and the training of personnel. Split responsibilities among government agencies with fragmented jurisdiction over aspects of food production and processing is a justification for establishing a separate stand-alone food safety agency.

People infected with the outbreak strain of E. coli O157:H7, by date of illness onset*

*n=210 for whom information was reported as of June 27, 2018. Some illness onset dates have been estimated from other reported information.