Study to Central Coast growers: don’t blame wildlife for E. coli outbreak.
Thursday, April 23, 2009
It may be too early for Salinas Valley growers to tear down deer fencing or return frog poison, but a recently released study indicates wildlife isn’t a huge threat for contaminating crops with E. coli bacteria.
The study found less than one half of 1 percent of Central Coast wildlife tested positive for the dangerous strain E. coli 0157:H7. Following a massive E. coli outbreak linked to San Benito County spinach in 2006, retailers pressured growers to rip out vegetation, shoot deer and take other drastic measures to keep wildlife out of their fields.
“SPENDING ALL THIS MONEY TO KEEP WILDLIFE OFF PROPERTY ISN’T THE END ALL AND BE ALL.”
“What they were doing before was just based on fear and conjecture,” says Terry Palmisano, a Monterey-based senior wildlife biologist with the California Department of Fish and Game. “Now we finally got some numbers to put behind this towards some good science. If wildlife are not the true sources of E. coli, they are merely carriers. Then spending all this money to keep wildlife off their property isn’t the end all and be all.”
Since the results are preliminary, however, the study is unlikely to trigger immediate changes to the state Leafy Green Products Handler Marketing Agreement, a voluntary set of farming and processing practices adopted after the 2006 outbreak. Still, Joe Pezzini, chairman of the Leafy Green advisory board and chief operating officer of Ocean Mist Farms, says the results are encouraging. “This is exactly the kind of research that helps us create better standards,” he says.
The study, conducted by UC Davis, DFG and U.S. Department of Agriculture, took 866 wildlife samples from 2007 through 2008. Only four animals – one wild pig, one coyote and two tule elk – came back positive for E. coli. None of the 311 black-tailed deer tested carried the pathogen.
But Michele Jay-Russell, co-investigator of the study and program manager at UC Davis’ Western Institute for Food Safety and Security, cautions against ruling out wildlife as a factor in the E. coli equation. “[Wildlife is] a low level of risk, but not a zero level of risk,” she says, pointing to a 15 percent positive E. coli match among wild pigs during the 2006 investigation. While E. coli was detected in pig and cattle feces near the Central Coast farm, an exact source was never discovered.
Jay-Russell says growers should continue to follow the agricultural practices in the marketing agreement, adding that the controversial practices of poisoning wildlife and pulling out non-crop plants – including hedgerows and erosion control grasses – are not a part of the pact. But some produce buyers have required growers, especially suppliers of bagged salads, to go above and beyond the agreement and take a scorched-earth policy.
Rob Gularte, co-owner of Rincon Farms in Chualar, says he has had to plow over crops when animal tracks were found in a field. “We have people watching around fields,” he says. “That’s important to build consumer confidence in the product.”
The study will strengthen the case for keeping riparian habitat intact, Gularte adds, noting that no birds or rodents tested positive for E. coli. “Fifty percent of the E. coli was found in elk,” he says. “The last time I checked there aren’t many elk around here.”
Palmisano hopes retailers get the message and stop requiring growers to put up fencing and shoot deer. “We don’t necessarily have to sell the farmers on this; we have to sell the buyers,” she says. “And the buyers are not the ones that come to the meetings and work with us.”
It will be at least another year before the wildlife study of 2,400 samples is completed, Jay-Russell says. Wildlife is part of a broader study examining water, soil and livestock to determine how E. coli moves through the environment and contaminates food.
Farrar says Zero, who is trained to detect E. coli and salmonella, was used in two outbreak investigations in the past year and half, including one in the Salinas area. “[Dogs] were able to identify this fecal material in weeds and areas that would be very difficult for average investigators to find,” he says.
Farrar admits growers have been hesitant to allow a territory-marking dog in their crops: “We have taken great pains to ensure the dog doesn’t defecate in the fields.”
The grant-funded pilot project will also explore using dogs to inspect produce imports and screen poop samples coming into the laboratory. Growers like the idea of using pooches before planting crops to prevent future outbreaks, he says.