Risk-assessment model factors in 
weather, distance from CAFO

While nearby concentrated animal feeding operations (CAFOs) have been suspected in a few E. coli O157:H7 produce outbreaks, little data exists about how far potential contamination risks may extend and weather’s role.

Kerry Cooper, Ph.D.

University of Arizona

Project Abstract

Although the MARC facility is far removed from most leafy green production, Cooper said it had several advantages that lent itself to research. For example, the USDA provides Cooper’s team complete access to the feedlot and cattle for sampling, something that would be impossible elsewhere.

The researchers established 24 sample sites radiating in eight directions from the feedlot center, with distances varying from 100 meters to 1,500 meters, or roughly a mile. Each site consists of two sets of soil, air, water and surrogate plant surface sampling.

Because it would be nearly impossible to cultivate a leafy green crop at the sites, Cooper said they tried to use a synthetic surface to act as a plant leaf stand-in. But the approach proved ineffective. In the meantime, the researchers are clipping vegetation at the sample sites to see if pathogens have colonized them.

“It’s not perfect, but we’re working on tweaking suggestions from the industry folks to come up with a better surface,” he said.

The researchers plan to collect samples every two weeks from May through September for two years. In addition, they’ll use whole genome sequencing to genetically compare the cattle E. coli O157:H7 strain to those in their samples to confirm transmission from the animal operation.

On the west end of the feedlot is a tree line, which Cooper said they’re also going to monitor to determine its potential role in pathogen dispersion.

At the suggestion of the CPS advisory committee, Cooper added student workers to collect flies possibly emanating from the feedlot and assay them for E. coli O157:H7 following protocols.

As part of the project, the researchers also will collect data from on-site weather stations and conduct enhanced sampling before and after extreme weather, such as flooding, high winds and severe storms. That data will be merged with additional drought and weather indices and wildlife migration information to assess other potential transmission sources.

The researchers will then use the information to develop risk-assessment and predictive models for potential produce contamination based on positive samples, persistence and varying distances from an animal feeding operation.



“We’re trying to gather some key data but also some predictive data to see how we can build off of this to help the industry,” Cooper said.

While the researchers are conducting their work with cattle, he said the general risk-assessment concepts should be applicable to other types of animal feeding operations.

“Our goal is hopefully to create a general model that shows (vegetable) producers what they need to be concerned about,” he said.

View - Project Page, Kerry Cooper, Ph.D., "How does weather influence transmission of E. coli O157:H7 from animal operations to produce fields?"

For more information:

Phone: 530-557-9761

Email: info@centerforproducesafety.org

Website: www.centerforproducesafety.org