Wild boar has been linked to the E. coli outbreak in September that sickened 204 people in 26 states and one Canadian province, and left three people dead.
In addition health authorities announced at a Thursday night press conference, nine samples of the bacteria found on one ranch in California's Salinas Valley match both the contaminated fresh spinach as well as the human "isolates" from the outbreak.
Dr. Kevin Reilly, deputy director of the prevention services division for the California Department of Health Services, said, "Clearly, we have positive results on one property that are helping to refine our investigation. We have not closed any possibilities on three other [nearby] ranches, but the information is accumulating that our environmental findings are consistent on this one property."
The samples of E. coli were found in a water sample in a creek, from cattle fecal specimens and in the gastrointestinal tract of a wild boar on the property. Reilly said that none of the nine positive matches came from a nearby spinach field which was the source of the contaminated produce.
Wild boars are assumed to have been responsible for bringing E. coli from the ranch to the spinach field.
Reilly said," Animals, wildlife and water were in close proximity to the field. We have evidence for fences torn down, wildlife going into the actual spinach fields themselves. That's where the investigation is centered right now. There's clear evidence that the pig population has access and goes onto the fields. Is that the ultimate means of contamination or is that one potential means, including water and wildlife? We're still investigating that."
Investigations are still continuing into three other ranches in the Salinas Valley. Although several E. coli samples were found there, none of them matched the outbreak strain when put through more advanced genetic testing.
Reilly said, "It is not unusual or unexpected that we would find E. coli associated with domestic cattle and/or wildlife but, to date, we have not matched it up with the outbreak strain other than on the single ranch."
Although authorities have not identified the ranch they did mention the presence of a beef cattle operation and fields where spinach and other ready-to-eat produce were grown. Agricultural and health authorities have long expressed their concerns about the proximity of fresh produce fields to farm animals.
Jack Guzewich, director of the emergency coordination and response staff at the U.S. Food and Drug Administration's Center for Food Safety and Applied Nutrition said, "We're definitely concerned about the spread of organisms in fields, and that's why we're working with [the agriculture] industry to encourage them to come up with practices to prevent this kind of contamination."
Earlier health officials had pointed the source of the E. coli outbreak to one processor, Natural Selection Foods, in San Juan Bautista, Calif following which they recalled all of its spinach products with use-by dates of Aug. 17 to Oct. 1.
Only this, the FDA said that consumers could resume eating fresh spinach. Health officials again said that fresh spinach was safe to eat at the Thursday night press conference.