As a result of the then-ongoing Coronavirus pandemic, the 11th Annual CPS Research Symposium was conducted virtually over the course of five consecutive weeks in 2020.
In Session 3 we reviewed three final reports and one interim report on produce safety research projects examining mitigations for frogs that intrude on produce fields, the potential cross-contamination risks posed by co-managed farms where cattle and poultry are raised in close proximity to fresh fruits and vegetables, and the risks posed by Cyclospora when resident in irrigation water. These outstanding presentations and discussions generated the following executive summary and more lengthy Key Learnings.
These learnings are meant to inform and provoke thought with an eye towards inspiring readers to examine their own produce safety programs and to use the research to make improvements. They are not meant as a directive on what must be done to produce safe food.
This and other recordings of CPS webinars are available via CPS’s website. The latest information about specific research projects mentioned in this document is available via CPS’s website, including our extensive research database and other produce safety resources.
Key Learnings Executive Summary
- A strategic fence can be good for everyone. Intrusion by frogs and other amphibians into produce fields can be impeded by using fences equipped with a lip that prevents the frogs from climbing over. It is important that the fence be constructed of a material that is rigid enough to withstand high winds and tall enough so the frogs cannot just jump over the fence.
- Environmentally sound solutions can be found that fit with produce safety goals. Employing fencing to control frogs is an example of a holistic, biological systems approach to solving a produce safety challenge. The biology of the frogs’ toe pads and the recognition of the mating behaviors of frogs and their movements following rainfall events guided the researchers to develop an effective barrier and the ability to position the barrier strategically to prevent entry into fields. In this way, frogs remain an important part of the ecosystem and the grower has a solution to manage the risk of contamination.
- Vegetative buffer zones can be leveraged to control the movement of airborne pathogens. Rapid growth vegetative buffer zones can be an effective tool in controlling airborne pathogens. A four-level vegetative buffer zone constructed with different height trees, shrubs, and grasses was shown to trap pathogens emanating from an adjacent poultry and dairy cattle operation on an experimental co-managed farm. Over the course of the two-year project, 11 produce samples were positive for STEC or generic E. coli and only one produce sample was positive for Salmonella, whereas 77 samples positive for STEC, generic E. coli or Salmonella were detected in the vegetative buffer zone, air, soil, and on manure in the poultry and dairy cattle areas. This indicates that vegetative buffer zones can help control pathogen movement into produce fields.
- Once again, a “one size fits all” approach will not work. Since no two co-managed farms can be identical in terms of risk, the deployment of vegetative buffer zones needs to be tailored to the specific characteristics of the operation. Animal types, densities, distances to produce fields, wind patterns, weather and other factors need to be considered when constructing buffer zones.
- Improved testing for Cyclospora. New detection methods for Cyclospora have made it easier to detect in irrigation water sources. Over the course of three years of testing, an average prevalence of 7% Cyclospora positive samples was observed in Yuma area irrigation canals. Importantly, new DNA-based testing methods for Cyclospora do not distinguish between live oocysts and dead oocysts so the public health risk of a positive Cyclospora test is not clear. Since Cyclospora must pass through humans, the prevalence rate means that wastewater from sewage treatment plants or other sources containing human wastes are likely infiltrating the canal system. Adherence to good agricultural practices like inspection of irrigation water sources to make sure they are not compromised by effluents from sewage treatment plants and monitoring the health of workers and providing facilities and enforcing strict handwashing practices remain important tools for controlling this risk.
This is the Key Learnings Executive Summary only. See the PDF link for more extensive information.