After wild pigs were linked to the deadly E. coli outbreak in California spinach nearly three years ago, Central Coast growers started shooting and poisoning wildlife.
Workers on one large farm killed 33 deer in a single year. Farmers poisoned ponds to get rid of frogs, ripped out trees and bushes and erected miles of expensive fencing.
But two years of testing wild animals and birds in the region suggests that only a small fraction actually carry the strain of Escherichia coli responsible for the contamination.
The results, released by the state Department of Fish and Game this week, "show that wildlife are not the Typhoid Marys some people think they are and some of the extreme measures are not necessary," said state wildlife biologist Terry Palmisano.
As part of an ongoing study of the pathogen, researchers collected samples from 866 animals, including 311 black-tailed deer, 184 feral pigs, 73 birds, 61 rabbits, 58 tule elk, squirrels, mice, skunks and coyotes.
Only four -- from a pig, a coyote and two elk -- tested positive for the lethal bacterium, E. coli 0157:H7. That is slightly less than half of 1%.
Three people, including a toddler, died in the spinach outbreak in the late summer of 2006. Federal authorities estimated that several thousand people were sickened across the country.
The contamination was traced to spinach grown on a cattle ranch east of Salinas. Although the precise source was never determined, the virulent E. coli was found in river water as well as in feces from cattle and wild pigs on the ranch.
The produce industry later adopted a voluntary set of standards for growing and handling leafy greens that amounted to a big "Keep Out" sign for any wildlife considered potential carriers of E. coli 0157:H7.
Big produce buyers also struck their own safety agreements with farmers, calling for even more precautions.
Requests jumped for state depredation permits allowing farmers to shoot wildlife damaging their crops. Growers who might otherwise have tolerated a deer browsing some lettuce shot the animals, fearing they couldn't sell a crop if safety auditors found droppings or tracks in a field.
"The buyers don't want even mice getting close," Palmisano said.
Baited PVC pipes with traps are a common sight along the edge of fields. Much of the Salinas River has been fenced. Grass along irrigation and runoff ditches has been dug up, leaving wide strips of bare ground.
"Folks are having to do stuff they don't want to do in order to sell their crop," said Paul Robins, executive director of the Monterey County Resource Conservation District.
In a 2007 survey by the district, one grower reported he had lost $17,500 worth of a crop because there were deer tracks in a field. A harvest was stopped when frogs and tadpoles were found in a creek.
The district's program director, Melanie Beretti, said farmers are resisting anti-erosion and water quality projects that involve vegetation that could attract wildlife.
She cited a strawberry grower who wanted to plant a hedgerow next to a long ditch. He dropped the idea because another farmer sometimes grew leafy greens in the field and couldn't plant within 50 feet of the shrubs.
Hank Giclas, vice president of the Western Growers Assn., said farmers are caught in a bind between satisfying wholesalers' demands and conservation practices.
"We're very supportive" of the E. coli study, he added. "We want to fundamentally understand where the risks are -- and are not -- and have designs that minimize the risk with the least negative impact on the environment in which people farm."
But he said his group, which helped draw up the voluntary standards, would wait until the research was finished before taking any action on the guidelines. In the meantime, an effort is underway to expand the safety program nationally.
The E. coli testing is part of a broader investigation by government and university scientists that will sample livestock, water and soil. More wildlife will also be tested.
"You can't make the interpretation yet that there is not a problem with wildlife," said Robert Mandrell, the lead researcher and a microbiologist with the U.S. Department of Agriculture. "But so far the data don't indicate there is a major red flag here."
For the survey, fish and game workers collected fecal samples from freshly killed deer and live animals and birds that were trapped and released. One technique is to place birds in a brown paper bag to collect droppings. But for the most part, fish and game spokesman Harry Morse said, "gloves and little bitty jars" are used.