The best approach to reducing incidences of foodborne illnesses in U.S. produce is prevention.
And frequent hand washing may be one of the most important preventive steps a produce facility manager or a grower can encourage employees to take to reduce risks.
“Prevention is the key,” said Patrick Hiller, Texas AgriLife Extension, delivering a talk prepared by Extension vegetable specialist Joe Masabni, who was unable to attend the recent Texas Plant Protection Association annual conference in College Station.
Masabni’s remarks indicated that recent foodborne illness outbreaks focused more attention on the produce industry, resulting in recent legislation to address the issue.
Good Agricultural Practices (GAPS) are being adopted by the industry to reduce potential for contaminants infecting produce and causing illness for consumers and workers.
From 1998 through 2008, 72 outbreaks involving contaminated produce were reported. Crops involved included lettuce, tomatoes, green onions and cantaloupes.
Contamination comes from three areas—chemical, physical and pathogens. “Pathogens are the most common contaminant,” he said.
Chemical contamination includes lubricants, cleaners, sanitizers, coating and pest control products. Physical contaminants include glass, wool, stones, insulation, plant parts and other foreign materials.
“Microbial contaminants are the most common cause of foodborne diseases,” Masabni said. ‘Most are present in the field.”
E-coli, Salmonella, Shigella and Listeria are all possible agents of foodborne illnesses.
“There are more than 200 different types of E-coli,” Masabni said, “and only a few of those affect humans.”
Fecal matter from humans, deer, sheep, goats, and insects may carry E-coli.
Salmonella also comes from fecal matter. “We have more than 2,000 types of Salmonella,” Masabni said, “and again very few affect people.”
Salmonella may be found in fecal matter from people, rodents, fowl, insects and snakes.
Shigella is a bacteria “more common in restaurants than in produce. It causes the third most common foodborne illness.”
“Listeria occurs in the soil, not fecal matter,” Masabni said. It can be deadly. “Mortality rate with Listeria is about 20 percent compared to 4 percent with Salmonella. It doesn’t multiply rapidly in the soil but can stay in pond water for 60 days or more.”
Raw manure is often a culprit in contaminating produce. “Pathogens have been found to survive in raw manure for one year, so it’s best not to use manure on produce. Keep fresh manure away from produce.”
Feedlots surrounded by crop land could also be cause for concern. Manure could move by wind or heavy rain into the nearby produce fields.
Masabni said properly composted manure reduces potential for contamination. In a publication on organic production he addresses using manure in vegetables.
Issues with manure
“There are food safety issues arising from the use of manure in that animal feces contain high levels of human pathogenic organisms which can be transferred to crops on which it is used. Aged or properly composed manure tends to reduce the risk from the use of animal waste materials. However, it is important that all farms using manure follow good agricultural practices to reduce any microbial risk that may exist. These include:
- Consider the source, storage, and type of manure.
- Store manure as far away as practical from areas where fresh produce is being grown and handled. If manure is not composted, age the manure at least six months prior to field application.
- Where possible, erect physical barriers or wind barriers to prevent runoff and wind drift of manure particles.
- Store manure slurry for at least 60 days in the summer and 90 days in the winter before applying to fields.
- Compost manure using proper temperature and turning techniques.
- Plan manure application in a timely and careful manner.
- Apply manure in the fall or at the end of the season to all planned vegetable fields, preferably when soils are warm, non-saturated, and cover-cropped.
- Use only properly decomposed manure on crops like lettuce and leafy greens.
- Avoid planting root or leafy crops in the year that manure is applied to a field.
- Incorporate manure into the soil.
- Do not harvest vegetables until 120 days after manure (is applied) if possible.
- Document rates, dates and locations of manure applications.
After-harvest sanitation is also critical. Hygiene is the basis for good practices and proper hand washing is the key. “Wash hands for at least 20 seconds before beginning work with produce,” Masabni said.
He also recommends checking worker health daily. “A big percentage of contamination comes from sick workers.”
Watching for foodborne illnesses in employees is also important to assure their safety. Masabni said symptoms to look for include loss of consciousness, nausea, sweating or fever and abdominal cramps.
“Educate employees about good agricultural practices,” he said. “The Extension Service offers GAP training.
“But prevention is the key and proper hand washing is the best method to reduce potential for contamination. And make certain to prevent raw manure contamination.”