RespiteMatch.com Health Blog

Exact strain of bacteria in outbreak found in dung near spinach field.

By Dorsey Griffith - Bee Medical Writer
Published 12:00 am PDT Friday, October 13, 2006

Cow dung from a cattle operation next to a spinach field implicated in the recent E. coli outbreak has tested positive for the exact same strain that sickened 199 people and killed three in the United States in recent weeks, federal and state health officials announced Thursday.

The finding represents the first time in more than a decade of outbreaks from lettuce or spinach that investigators have matched the precise E. coli strain found in ailing humans to tainted produce they ate and the fecal matter that contaminated the food.

But experts still must hunt for the means by which the contamination spread to the produce.

And they are still testing specimens taken from three other ranches where spinach implicated in the outbreak was grown.

“We need to follow this to find out where the science leads us,” said Kevin Reilly, deputy director for prevention services at the California Department of Health Services.

Dr. Robert Brackett, director of the Center for Food Safety and Applied Nutrition, said, “When you have identical matches of DNA, you assume they are from a common source. Having said that … we need to find out how prevalent it is.”

Reilly would not divulge the name of the ranch where the cow manure in question was found, but said it was one of four still under investigation in Monterey and San Benito counties. A handful of ranches in San Mateo County, once a focus of the probe, are no longer implicated, he said.

Reilly confirmed, however, that the ranch is leased to both a beef-cattle operation and a spinach grower, and that the two enterprises are separated only by a paved road.

“The fields are surrounded by pastures where livestock are kept,” Reilly said. “The locations where we collected the positive fecal specimens were between a half-mile and mile from the field itself.”

Health officials said there are any number of possible ways in which fecal matter from a nearby cattle pasture could migrate onto a nearby field, and that all of those are under investigation.

They include: contamination of the water used to irrigate the crops, floodwater and other runoff, farm worker hygiene, composted manure used for fertilizer, farm equipment and wildlife that do not recognize ranch boundaries.

Wild boar, for example, are very common in the area, Reilly said.

“We have witnessed on site where they have torn through fencing, gone under the fencing and they have the ability to access fields,” Reilly said.

Both Reilly and Brackett emphasized that Natural Selection Foods, the San Juan Bautista processor that packaged the tainted spinach, is not off the hook in terms of its role in the outbreak.

“At every step of the way we need to have preventatives and controls in place to reduce risk of contamination,” said Reilly, including in the processing plants.

“No one is off the hook,” added Brackett. “It’s absolutely essential that every one of the farms throughout the country, and especially in that area, are doing absolutely everything they can to make sure this doesn’t happen again.”

Calls for stepped-up regulation of the produce industry have heightened in the wake of the outbreak, the 20th from lettuce or spinach recorded in the past 10 years.

Nine of the outbreaks were traced back to the Salinas Valley.

For the past two years, the U.S. Food and Drug Administration has voiced concern about agricultural practices in the Salinas Valley, urging industry and the state of California to address possible sources of contamination. But the state and federal government largely rely on voluntary adherence to well-established growing and processing guidelines.

One area that may require regulation, Brackett conceded, is how close animal operations should be to growing fields.

“The proximity of farm animals to produce is something we will take into consideration in anything we go forward with,” he said.

Trevor Suslow, an extension specialist at the University of California, Davis, who works closely with the produce industry, said he knows of no existing regulation that would prohibit the two kinds of operations from locating near each other. Suslow added, however, that “good agricultural practices” would discourage it.

“The research clearly shows a gradient effect: the closer you are to a dairy operation, the more likely you will have indicator bacteria on that crop,” he said, citing generic E. coli as an example. “It raises the risk.”

Suslow said animals and humans can carry contaminated feces on their hooves or feet, spreading that bacteria to anything they come in contact with. He said E. coli also can survive in dried cow dung, which can become airborne and blown by winds onto adjoining fields.

Suslow said that while stronger regulations governing proximity of horticulture and animal agriculture may be in order, efforts to adopt them may be a challenge.

About the writer:
n n n The Bee’s Dorsey Griffith can be reached at (916) 321-1089 or dgriffith@sacbee.com.

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