Food safety risks at the fresh produce-animal interface: identifying pathogen sources and their movement on diversified farms.

A potential source of fresh produce contamination is the direct application or indirect transfer of animal manure into the produce farm environment. One clear knowledge gap that exists is in ascertaining the specific metrics and consequences of proximity at the interface of agricultural production involving food animals and fresh produce. Without this information, it is difficult to prescribe practical risk-reduction practices and expect producers to heed measures. This is especially true in case of “Diversified” farms where the integration of growing animal and fresh produce in close proximity predisposes the fresh produce to contamination by animal shed pathogens. To address this, we propose to 1) Identify sources of Salmonella, STEC O157:H7 and non- O157:H7 STEC on diversified farms and determine the impact of buffer distance on their movement at the animal: fresh produce interface; and 2) Validate the outcome of first objective by conducting a controlled study to determine source and the movement of indicators and pathogens at the animal: produce interface on the Piedmont Agriculture Research Station reflective of a diversified enterprise. We strongly believe that the study will result in identifying risk gaps and help the fresh produce industry to strategize control measures to prevent fresh produce contamination.

The emergence and growth of the “Eat Local” movement has contributed directly to the growth of diversified farms which promotes rearing livestock and growing fresh produce within the same agricultural system. The interface of food animals and fresh produce in agricultural production is an area in need of information that could potentially reduce the risk of pathogen transmission and freshproduce contamination. The primary goal of this project will be to determine the potential transmission of Salmonella, Shiga Toxin-Producing (STEC) Escherichia coli O157:H7 and non-O157:H7 STEC from animal operations that are in close proximity to vegetable production systems on an experimental research station and commercial diversified farming operations. To attain this goal, we propose to pilot a controlled study on an agriculture research station to determine the impact of multiple farm variablesincluding buffer zone distances, temporal factors, air and insect on transmission of the above pathogens between animals and fresh produce operations. Information collected from controlled studies will be complemented with data generated on commercial diversified farms which will help identify the key sources, track movement of pathogens, narrow the ‘how-to’ information gap, and help the produce industry to strategize control measures to improve food safety.

1) Conduct a controlled study to determine the impact of buffer zone distances, temporal factors, air and insect on the movement of indicator (fecal coliforms, E. coli and Enterococcus sp.) and pathogenic (Salmonella, STEC O157:H7 and non O157:H7 STEC) organisms at the animal:produce interface on the Piedmont Agriculture Research Station reflective of diversified farming systems. 

2) Validate the outcome of the first objective by studying the movement of pathogenic microorganisms from known animal reservoirs and potential environmental sources into fresh produce field in commercial diversified farms.

The focus was on pathogen transfer from animal operations to diversified vegetable farming practices, however, our findings are not limited to the sustainable agriculture environment since other cropping systems, including standard organic production, conventional farming practices, and biodynamic approaches, will also pose the risk of pathogen transfer when in close proximity to animal operations. Under these scenarios the size of animal operation, proximity to produce fields, and cultural practices seem to impact pathogen transfer to produce and these parameters are irrespective of farming approaches. Consequently, whether farmers are dealing with fruits, vegetables, tree nuts, horticulture, nursery crops, or others included within the definition of "specialty crops," our findings and potential approaches to reduce pathogen transfer could benefit any of them. For our second objective, we collected farm samples, including produce, animal and the environmental, from commercial sustainable farms in North Carolina and Tennessee. There were clear distinctions between the outcomes based on geographic locations of these farms in the two different states. Overall, Salmonella was isolated from multiple samples originating from commercial sustainable farms only in Tennessee and not in North Carolina. None of the fresh produce samples from the farms in either of the two states tested positive for Salmonella. In Tennessee, STEC was isolated from fresh produce and animal and environmental sources as well as flies, while in North Carolina only the fecal and soil samples tested positive. Our results strongly suggest that there needs to be a reassessment of the proposed 400-feet minimum buffer zone distance between animal operations and the location of fresh produce fields. Based on our study, this distance does not seem sufficient to prevent the transmission of pathogens from animal sources to produce. We suggest conducting quantitative studies at varying buffer zone distances to determine the adequate buffer zones to prevent pathogen transmission and the establishment/assessment of other physical barriers to potentially reduce pathogen transfer. Our recommendation for future projects, based on what we learned through this study, is to include funds to offset the financial burden to grower participants. The study has enabled us to form a consortium of fresh produce farmers in North Carolina who are now more eager and willing to collaborate with us on larger projects. We found that working closely with county-based extension staff on identifying and recruiting grower participants to be extremely valuable.