Following the completion of a "massive field study" researchers have reported the presence, albeit uncommon, of E. coli O157:H7 in wildlife in California’s central coast region. The findings were reported yesterday at the annual meeting of the American Society for Microbiology in San Diego. The occasional presence of E. coli O157:H7 in fecal samples of wildlife species including cowbirds, coyotes, crows, mice and feral pigs was reported.
The impetus for the study was the 2006 outbreak of E. coli O157:H7 in bagged spinach grown and processed in the region. The outbreak caused at least 205 illnesses and five 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 incidence of E. coli O157:H7 in the tested wildlife was perhaps somewhat lower than expected:
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 in California. All three counties are home to farms that grow fresh spinach, lettuce and other produce.
Laboratory tests revealed that E. coli O157:H7 was present in 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.
The relatively low incidence of the bacteria in wildlife stands in contrast to the large number of E. coli O157:H7 outbreaks tied to leafy greens from the area. Thus, researchers are left to ponder other potential sources and explanations.