A trait-based framework for predicting foodborne pathogen spillover from wild birds

Olivia M Smith and Joseph M Taylor, Department of Entomology, University of Georgia, Olivia M Smith, Kevin Cornell, Johnna Eilers and Chika Sato, School of Biological Sciences, Washington State University, Elissa M. Olimpi, Wildlife, Fish, and Conservation Biology, University of California, Davis, Davis, CA, Nora Navarro-Gonzalez, Oniris, BIOEPAR, INRAE, Luke Frishkoff, Department of Biology, University of Texas at Arlington, Arlington, TX, Tobin D. Northfield, Tree Fruit Research and Extension Center, Washington State University, Timothy M. Bowles, Environmental Science, Policy, and Management, University of California Berkeley, Berkeley, CA, Amanda Edworthy and Jeb P. Owen, Entomology, Washington State University, Pullman, WA, Zhen Fu, Department of Entomology, Washington State University, Karina Garcia and David J Gonthier, Entomology, University of Kentucky, Matthew Jones, Tree Fruit Research and Extension Center, Washington State University, WA, Christina M. Kennedy, Development by Design, The Nature Conservancy, Fort Collins, CO, Christopher E Latimer, Global Protect Oceans, Lands and Waters Program, The Nature Conservancy, Erin E Wilson-Rankin, Department of Entomology, University of California, Riverside, William E. Snyder, Entomology, University of Georgia, Athens, GA, Daniel Karp, Wildlife, Fish, and Conservation Biology, University of California, Davis, CA

Background/Question/Methods
Fear that wildlife carry foodborne pathogens into farm fields has created strong pressure on growers to deter wildlife from entering their farms. Birds are of particular concern as they cannot be easily fenced, regularly frequent farm fields, and are known to occasionally carry pathogens. As a result, many produce growers are removing habitat around farms and are no longer allowed to use nest boxes to attract pest-eating birds to their farms. Critically, managers of agroecosystems lack data to determine the risk associated with different bird species and between landscapes and farms with high vs. low amounts of surrounding seminatural habitat. Collecting sufficient pathogen testing data to determine food safety risks for the hundreds of bird species inhabiting agroecosystems is highly unrealistic due to the time and financial costs of doing so. Using >11,000 tests of Salmonella spp., Shiga-toxin producing E. coli, and Campylobacter spp. and 1,565 bird surveys covering 139 bird species from >350 locations across the western U.S.A., we used a “barriers-to-spillover” framework to examine the importance of 11 traits in mediating wild bird risk to food safety. We tested whether traits associated with pathogen exposure (e.g., habitat use, movement, and foraging strategy) and pace-of-life (clutch size and generation length) mediated foodborne pathogen prevalence and proclivities to enter farm fields and defecate on crops.
Results/Conclusions
Our efforts yielded at least four insights of potential interest to scientists, managers, and policymakers. First, Salmonella spp. and Shiga-toxin producing E. coli are very rarely detected in birds (0.46% and 0.22% prevalences, respectively), but Campylobacter spp. is more common (8.0%). Second, we found that traits related to pathogen exposure substantially increased pathogen prevalence; most notably, species associated with cattle feedlots were more likely to shed Campylobacter spp. Third, we found that species associated with feedlots were also more likely to enter fields and defecate on crops. Fourth, we found that insectivorous and canopy-foraging species were less likely to carry pathogens and enter farm fields, respectively. Our results suggest that separating crop production from livestock farming may be the best way to lower food safety risks from birds. However, promoting insectivorous birds may represent a win-win-win for bird conservation, crop production, and food safety. More broadly, our trait-based framework suggests a path forward for co-managing wildlife conservation and food safety risks in farmland by providing a strategy for holistically evaluating the food safety risks of wild animals, including under-studied species.