Sep 14, 2006 (CIDRAP News) – Outbreaks of Escherichia coli in recent years have spurred federal and California officials to launch a broad investigation into farms and processors of lettuce and other leafy greens in California's Salinas Valley, according to the US Food and Drug Administration (FDA) and news sources.
Of 19 US outbreaks of E coli O157:H7 from lettuce and spinach since 1995, eight have been traced to Salinas Valley, dubbed the "Salad Bowl of the World," according to a Sep 11 Los Angeles Times article. These eight outbreaks have affected 217 people in eight states, including two elderly patients from northern California who died in 2003.
In response to these outbreaks, the FDA announced its Lettuce Safety Initiative on Aug 23 of this year. In its announcement, the FDA said it will, in conjunction with California agencies, "visit farms and cooling and packing facilities, and inspect processors, focusing on good agricultural practices and good manufacturing practices," identifying "practices that potentially lead to product contamination."
The initiative in Salinas Valley began Aug 28 and is scheduled to wrap up next month, a food safety official from the FDA's Center for Food Safety and Applied Nutrition (CFSAN) told CIDRAP News via e-mail. "We will be compiling the findings in the following months and hope to have a summary by next spring," he said.
In addition to CFSAN, the Salinas Valley investigation involves the FDA Office of Regulatory Affairs, the California Department of Health Services, and the California Department of Food and Agriculture, according to the official. He characterized the initiative as cooperative: "This is an important example of industry, government, and academia working together to understand a problem so that meaningful interventions can be identified."
About 40 farms, packers, and processors will be visited, he said.
Possible source for outbreaks
When asked about a likely source for the contamination, the official responded, "There are many possible sources of the contamination. There may not be one source, but a combination of sources [and] factors."
Craig Hedberg, PhD, a University of Minnesota expert on foodborne disease, said of the outbreaks, "I would suspect there might be a link between dairy production and lettuce contamination, but what that might be is unknown." Hedberg, of Minneapolis, is an associate professor of environmental and occupational health.
Past, smaller-scale investigations have identified a number of possible sources of contamination in Salinas Valley. The valley, located in Monterey County, grows nearly $1 billion in lettuce and other leafy greens each year, according to a story yesterday from the Monterey County Herald.
In a Nov 4, 2005, letter to California lettuce growers, packers, processors, and shippers, CFSAN director Robert Brackett, PhD, mentioned intermittent flooding from Salinas Valley creeks and rivers as a possible source of contamination. He cited a 2005 report that identified O157:H7 E coli in the valley's watershed and stated that any ready-to-eat crop that comes in contact with floodwaters is not fit for human consumption.
In addition, in a January letter to the Western Growers Association, California Public Health Officer Mark Horton, MD, MSPH, wrote that his staff will be reassessing manure composting and septic system regulations. In addition to citing the possible flooding problem, the letter also specified assessment of workers' access to toilets and hand-washing facilities, as well as adherence to other health-safety rules.
Other possible contamination sources listed in the Los Angeles Times article include bird and other animal droppings and dust from nearby cattle fields.
Rare E coli strain in Utah
In related news, Utah health officials implicated Salinas Valley lettuce as a possible source for an E coli outbreak in their state in June, according to an Aug 20 Monterey County Herald story.
The Utah outbreak affected 73 people, including three who experienced kidney failure. It involved a different, rare strain: O121:H19.
Both the O121:H19 and O157:H7 strains occur naturally in the digestive system of cattle and humans. But eating food contaminated by the bacteria can cause abdominal pain, diarrhea, other serious symptoms such as kidney failure, and death, according to the Herald story.
Which underscores the importance of the just-launched probe. The CFSAN spokesperson said of the effort, "We do not know why we are seeing E coli O157:H7 in leafy greens. . . . We hope that research [from the Lettuce Safety Initiative] will better explain what is going on."
Aug 23, 2006, FDA announcement of its Lettuce Safety Initiative