Daniel Karp, Ph.D., with the University of California-Davis, is examining the prevalence of different wild bird species in agriculture and whether they carry and transmit foodborne pathogens. Karp is also developing a photographic guide to help growers identify birds and the potential food safety risks they may pose.
The project is titled, “Towards a holistic assessment of the food-safety risks imposed by wild birds” and its co-principal investigator is Jeffery McGarvey, Ph.D., with the U.S. Department of Agriculture’s Agricultural Research Service.
“We’re trying to figure out how we can co-manage these agricultural systems for food production, food safety, and bird conservation at the same time,” Karp said. “It’s not like you can exclude all birds from farms. We’re trying to understand the relative risks of different species and how farm management affects those risks.”
The project is collecting fecal samples from birds caught in fields and assaying them for 3 pathogens, Campylobacter, Salmonella, and Shiga toxin-producing E. coli. The birds are banded before being released so they can be quickly identified if recaptured.
Crews also are conducting fecal transects, where they grid out an area, search for feces and sample any they find to determine how long pathogens survive in bird feces. So far, Karp said, they’ve collected about 1,000 samples. Using DNA testing, McGarvey is often able to identify the species from which the feces came and whether pathogens are present.
In addition, the researchers inoculated about 200 fecal samples from wild turkeys and Western bluebirds with E. coli in experimental field plots. The samples were placed on one of three different substrates — bare soil, plastic mulch or lettuce leaves — to determine how long pathogens survive in bird feces under field conditions.
“Early on, we wanted to know if the bird’s identity mattered or if survival just depended on the size of feces,” Karp said.
Preliminary results found both fecal size and the substrate type affected die-off, with the pathogens dying off faster in the smaller masses than in the larger ones. Bacterial survival also was lower on soil and plastic mulch than on lettuce leaves.
From their results, Karp said he plans to develop a holistic food safety risk assessment for farmland birds.
More on Karp and McGarvey’s research can be found here.
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