Location: Foodborne Toxin Detection and Prevention Research
Title: Assessing foodborne pathogen survival in bird feces to comanage farms for bird conservation, production, and food safetyAuthor
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SPENCE, AUSTIN - University Of California, Davis |
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McGarvey, Jeffery |
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Lee, Sang In |
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SMITH, OLIVIA - Michigan State University |
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OLIMPI, ELISSA - Virginia Polytechnic Institution & State University |
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YANG, WENTAO - University Of California, Davis |
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ZHANG, MEIRUN - University Of California, Davis |
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KARP, DANIEL - University Of California, Davis |
Submitted to: Journal of Applied Ecology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 10/11/2024 Publication Date: 1/20/2025 Citation: Spence, A., McGarvey, J.A., Lee, S., Smith, O., Olimpi, E., Yang, W., Zhang, M., Karp, D. 2025. Assessing foodborne pathogen survival in bird feces to comanage farms for bird conservation, production, and food safety. Journal of Applied Ecology. 2025;00:1–11. https://doi.org/10.1111/1365-2664.14853. DOI: https://doi.org/10.1111/1365-2664.14853 Interpretive Summary: Birds can harbor pathogenic bacteria in their gastrointestinal tracks and thus may be a food safety risk when they enter produce fields growing fresh ready to eat produce such as lettuce. We examined what type of birds are found in California lettuce fields and how often they carried pathogenic bacteria. We also examined various types of bird feces and determined how well pathogenic bacteria can survive in there feces. Our results indicated that most birds found in lettuce fields were of low food safety risk and that pathogen survival in feces was associate with fecal mass and not bird type. Technical Abstract: 1. Because birds can carry foodborne pathogens, there is widespread concern that birds impose food-safety risks to farms. Growers are thus often encouraged to deter birds and forego harvesting crops near bird feces (e.g., no-harvest buffers). Developing a holistic understanding of the pathogen spillover process – from individual infection to pathogen persistence on crops – is essential to understand and manage food-safety risks associated with birds. 2. Here, we coupled field experiments, greenhouse experiments, and bird surveys to understand the relative risks associated with different bird species on California farms. We first compared E. coli survival in bird feces on lettuce, soil, and plastic mulch to identify where pathogens are likely to persist. Next, we quantified pathogen survival in feces from 10 bird species to identify higher-risk species. Finally, we combined pathogen survival data with bird surveys and fecal transects to assess food-safety risks in crop fields across 29 California lettuce farms. 3. E. coli abundance rapidly declined in bird feces, but rates varied across substrates. E. coli survival was higher on lettuce compared to soil and plastic mulch, likely because of lettuce’s cooler and wetter microclimate. E. coli persistence was also much higher in feces from larger birds—which produce larger feces—than small songbirds. Importantly, minimal differences in persistence among species were observed after all feces were standardized to the same mass. 4. Though bird feces were common on farms, most birds entering farms, contacting crops, and defecating on crops were small songbirds that defecate small feces. Coupled with the fact that ~90% of feces were deposited on soil, these results suggest that most birds on farms present relatively low food-safety risks. 5. Synthesis and applications. Growers are often encouraged to deter all bird species and forego harvesting crops near all bird feces, but our work suggests not all birds and feces pose the same food-safety risks. If growers ignored small bird feces on soil, then we estimate that the area of California lettuce farms affected by no-harvest buffers could decrease from ~10.3% to ~2.7%. More broadly, our results suggest farmers could promote small, insect-eating birds by erecting nest-boxes or preserving habitat without necessarily compromising food safety. |