E. coli can linger in animal droppings, allowing it to be spread by weather and animal movement, according to initial findings from a multi-year Food and Drug Administration study of a major California produce-growing region.
A study spanning sites in a 7,000 square-mile area of California's Central Coast agricultural region found rangeland beef cattle, feral pigs, deer, birds, and coyotes were "frequent sources" of E. coli, according to survey findings released Thursday.
Researchers found the same strain of E. coli, a foodborne illness, in samples taken 15 months apart and 70 miles from each other, "providing evidence that wildlife may contribute to the movement of" E. coli in the region, according to a summary. E. coli isolated from wildlife feces collected from sites in the area genetically matched strains researchers found in the feces of other animals as well as surface water, sediment, and soil.
The study had sought to identify some of the environmental factors behind the introduction and spread of E. coli in the region, including several infections caused by one strain between 2016 and 2020. However, an FDA constituent update says in the survey, the scientists were not able to recover samples of that strain.
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Samples in the survey were taken from 14 livestock ranches, five produce farms, two composting facilities and two vineyards between August 2020 and May 2025.
Overall, scientists at FDA, the California Department of Food and Agriculture, and the Western Center for Food Safety at the University of California, Davis, isolated 68 E. coli strains, including six serotypes considered "highly pathogenic to humans." The summary says some of these serotypes persisted for nearly two years.
The researchers found higher prevalence of E. coli in wildlife feces from feral pigs, deer, birds and coyote compared to other wildlife. They did find positive samples in crow, raven, dove and hawk fecal samples, as well as bobcat and elk feces, according to the summary.
In terms of livestock, rangeland beef cattle feces had much higher contamination levels than those from sheep and horses. The bacteria were also detected in bison feces, but sample numbers were limited.
Researchers found the bacteria in some samples of older, dry feces, which indicates E. coli may "remain viable in fecal material for extended periods and may introduce risk if disturbed through animal actions or weather events."
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