DAVIS, Calif. ― Good agricultural practices already recommend fencing to exclude wildlife and livestock from production fields because some foodborne illness outbreaks have been linked to larger mammals.

But how much risk do smaller animals, such as birds, lizards and mice, pose?

That’s the question that two separate studies funded by the Davis, Calif.-based Center for Produce Safety seek to answer.

Researchers involved with both projects presented updates to attendees of the center’s third annual research symposium in Davis June 28.

One study, led by Michele Jay-Russell, program manager at the Western Center for Food Safety, University of California-Davis, looked at reptiles and amphibians as potential reservoirs of foodborne pathogens.

After all, several recent Salmonella outbreaks have been tied to pet turtles, she said.

According to the Centers for Disease Control and Prevention, currently there are investigation into five multi-state outbreaks linked to turtles. At least 124 people have become sick, according to the CDC.

“But do wild reptiles and amphibians carry them at all?” Jay-Russell asked.

Using live traps, she caught reptiles and amphibians from 10 farms and 44 sites along California’s Central Coast and sampled them for Salmonella and the virulent E. coli O157:H7 strain. In addition, she sampled the waterways in which the animals were caught.

Jay-Russell also worked with colleagues in Georgia who sampled reptiles, amphibians and pond water at five mixed-vegetable operations in the Suwannee River watershed.

Jay-Russell said she plans to continue the project for another season with the hope of developing recommendations to promote food safety and environmental goals.

Andrew Gordius, a staff toxicologist with the California Department of Fish and Game, Sacramento, tested 3,065 animals for E. coli O157:H7 and 1,082 for Salmonella in three California central coast counties.

Although the results showed very low infection rates among most bird and mammal species, Gordius said, “It’s important to understand the natural history of the birds.”

For example, birds that are gregarious and congregate in areas with high pathogen loads, such as blackbirds in stockyards, pose more risk should they move into fields than species that tend to be loners.

Based on his findings, Gordius recommended that growers add wildlife to the list of items, which includes soil, water, equipment and soil amendments, they already test annually.