E. coli rare in ‘salad bowl’ wildlife

The disease-causing bacterium E. coli O157:H7 is present but rare in some wildlife species of California’s agriculturally rich Central Coast region, an area often referred to as the nation’s “salad bowl,” says a long-awaited report from a team or researchers led by a University of California, Davis, scientist.

Key Points

• E. coli O157:H7 is present but rare in Central Coast wildlife species.

• Found in fecal samples of cowbird, coyote, crow, deer mouse and feral pigs.

• Farmers should continue to follow “good agricultural practices.”


The researchers, who are nearing completion of a massive field study to help identify potential sources of E. coli O157:H7 near Central Coast farms, presented their findings at the American Society for Microbiology in San Diego annual meeting.

Follow best practices

Based on their findings, the researchers recommend that farmers in this region continue to follow “good agricultural practices,” a set of accepted, on-farm procedures designed to protect crops from contamination during production and harvest listed online at ucgaps.ucdavis.edu.

The study was spurred by a 2006 nationwide E. coli O157:H7 outbreak linked to fresh, bagged spinach grown in California; the outbreak resulted in 205 reported illnesses and three deaths.

“The study helps us better understand the possible risk of crop contamination from wildlife, and allows us to compare that to the risk of contamination from other possible sources, such as livestock and irrigation water,” said lead study author Michele Jay-Russell, a veterinarian at UC Davis’ Western Institute for Food Safety and Security.

The results

From 2008 through 2009, the team collected and tested 1,133 fecal samples from wild birds and mammals on 38 private properties in Monterey, San Benito and San Luis Obispo counties.

Laboratory tests revealed E. coli O157:H7 in fecal samples from two cowbirds, two coyotes, five crows, one deer mouse and 10 feral pigs. Samples from deer, opossums, raccoons, skunks, ground squirrels and other bird and mouse species all tested negative for the bacterium.

Robert Mandrell, principle investigator and research leader from the USDA’s Agricultural Research Service, said that the discovery of a low level of E. coli O157:H7 among Central Coast wildlife was somewhat surprising.

“The fact that we have identified two bird species with an incidence of E. coli O157:H7 of more than 3%, feral swine with about a 4% incidence and several coyotes and rodents that tested positive for O157:H7 suggests there are at least several sources of pathogen movement in this region,” Mandrell said.

“We have no evidence that the concentration of the pathogen was high in the feces of the animals testing positive, so the significance of wildlife as a source of direct contamination associated with outbreaks remains unclear,” he said. Researchers are comparing the genetics of E. coli O157:H7 strains found in wildlife to strains from other sources, he added.

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OUTBREAK RESEARCH: This wildlife study of the Salinas Valley “salad bowl” was spurred by a 2006 nationwide E. coli O157:H7 outbreak linked to fresh, bagged spinach grown in California; the outbreak resulted in 205 reported illnesses and three deaths.

This article published in the September, 2010 edition of CALIFORNIA FARMER.

All rights reserved. Copyright Farm Progress Cos. 2010.