Summary
The purpose of this Rapid Response field study was to assess the potential public health hazard, within a unique on-farm data gathering opportunity, of a cantaloupe field adjacent to a small dairy operation. Our objective was to document the likelihood of presumed, localized dispersal of contaminants due to ag-traffic, animal activity, and other direct and indirect transfer of fecal indicators and pathogens from the animal facility before the intended initiation of harvest at that location. In addition, the Rapid Response opportunity permitted the assessment of commercial kits and in-house UC Davis developed molecular methods (up to six different methods) to detect EHEC and Salmonella enterica in melons harboring low levels of stress-adapted pathogen populations against a high background of microbial populations and adhering soil.
Research Objectives
The purpose of this Rapid Response field study was to assess the potential public health hazard, within a unique on-farm data gathering opportunity, of a cantaloupe field adjacent to a small dairy operation. Our objective was to document the likelihood of presumed, localized dispersal of contaminants due to ag-traffic, animal activity, and other direct and indirect transfer of fecal indicators and pathogens from the animal facility before the intended initiation of harvest at that location. In addition, the Rapid Response opportunity permitted the assessment of commercial kits and in-house UC Davis developed molecular methods (up to six different methods) to detect EHEC and Salmonella enterica in melons harboring low levels of stress-adapted pathogen populations against a high background of microbial populations and adhering soil.
Findings & Recommendations
In this study, production of melons intended for commercial marketing were grown in close proximity to a dairy cattle facility. Proximity issues due to animal presence and activity, abundant vector potential between the dairy and the crop, as well as crop and dairy-related human activity appear to have significantly compromised the safety of this crop. However, the pre-plant application of manure and lagoon waste, including prior applications over a long period of time, appear to have made the establishment of clear spatial buffer and gradient between the AFO and cantaloupes targeted for harvest impossible. While we feel that a case for in-season transfer of STEC from the AFO, within 200 feet of the eastern boundary, might be made scientifically the risks associated with this site necessitated and supported the full crop-destruct decision. Within this opportunity to evaluate natural persistence and contamination events, our findings clearly and strongly support existing guidance to maximize the distance between agricultural operations (fresh produce production) and animal activity, however it remains inconclusive to establish a science and data-based spatial limit. We feel broad dissemination of the results from this study, especially the documented spatial distribution of fecal indicators and pathogenic bacteria in both crop and soil across a large parcel, will be of significant value to the research community and public health agencies in refining ag-environmental sampling plans for food safety assessments or outbreak investigations. Equally, the key outcomes from this Rapid Response study site may be used by industry to reassess or validate current and evolving standards.