Salmonella, a pathogen generally associated with undercooked chicken and raw cookie dough, keeps appearing in our salads. At a time when Americans are being encouraged to eat more fresh fruits and vegetables, both growers and the government are struggling to keep them safe.
From 1998 to 2008, the Centers for Disease Control and Prevention linked 12 deaths and 8,570 illnesses to salmonella in produce, according to a News21 analysis of CDC data. The infection causes diarrhea, fever and abdominal cramps for up to a week. In severe cases, patients may require hospitalization, and the infection can be fatal if it spreads to the bloodstream.
Controlling salmonella in produce has proven to be elusive, not only because there are many unanswered scientific questions, but also because the nature of fruits and vegetables makes them more vulnerable to contamination.
Pathogens are killed by heat, but produce is often consumed raw. Also, the surfaces of fruits and vegetables – covered with microscopic holes and fissures – are great hiding places for salmonella from contaminated water and infected animals. If the germs grow into the fruit, like into the netted rind of a cantaloupe, no amount of scrubbing will remove them. (Related story: Salmonella Outbreak Traced to Cantaloupes)
After a cluster of produce-related outbreaks in the mid-’90s, the Food and Drug Administration began seriously addressing the issue of produce safety. In 1998 the agency created voluntary food safety guidelines for growers and shippers, commonly referred to as Good Agricultural Practices, or GAPs.
Because standards could not be written specifically enough to address the concerns of individual fruit and vegetable operations, the GAPs were not created as mandatory regulation.
With the signing of the Food Safety Modernization Act (FSMA) earlier this year, growers and producers for the first time will be required to follow produce safety standards.
The FDA has turned to the produce industry to help write the rules mandated by the FSMA, although their implementation and enforcement could be hindered by potential budget cuts looming over the agency. In the last few years, the industry has implemented voluntary commodity-specific standards to help ward off infectious outbreaks, and the FDA wants to include these standards in its new rules. But industry leaders acknowledge that some of the standards lack the science to back them up.
In the midst of a 2008 outbreak of salmonella that initially was falsely blamed on tomatoes, Florida became the first state to require mandatory government inspections and audits for those who grow and/or process tomatoes.
In 2007, a widespread E. coli outbreak eventually linked to a California spinach processor led farmers in that state to form the California Leafy Green Products Handler Marketing Agreement (LGMA) to improve safety and restore public confidence in the devastated industry.
Salmonella remains the biggest foodborne threat in this country. While the rate of E. coli O157:H7 infections has been cut in half over the past 15 years – and the incidence of some other types of foodborne illness also has declined – the rate of salmonella infection has gone in the other direction, increasing by 10 percent in recent years, CDC reports.
Produce remains an area of concern: From 1998 to 2008, there were 120 salmonella outbreaks tied to produce, compared with 53 from E. coli, the News 21 analysis found.
The progress in fighting E. coli is attributed in part to cleaner slaughterhouses and improved inspections of processing plants. But agricultural research on produce and other crops is costly and time-consuming and must address the individual concerns of specific commodities, researchers say. Different regions have different geographies, microclimates and wildlife issues. Irrigation water comes from different sources: In California’s Salinas Valley, for instance, growers rely on deep wells; in Florida, they use canal water.
“You can’t really do research that covers every variation, every nuance, every microbiological difference,” said Trevor Suslow, extension research specialist at the University of California, Davis.
Scientists and farmers do know that salmonella can enter the food supply through what they refer to as the “four Ws”: water, wildlife, waste and workers. But they are still decoding just much how each factor contributes to contamination – and how to stop it.
For example, contaminated water can contaminated produce. But neither the industry nor the government has developed standards for irrigation water quality. So, California’s LGMA adopted the Environmental Protection Agency’s standards for recreational water – which test for generic E. coli.
Generic E. coli, a bacterium that lives in our guts, is not necessarily harmful but is an indicator of fecal contamination. Too much generic E. coli in the water may be a sign that harmful bacteria such as E. coli O157:H7 and salmonella are also present, although some researchers disagree. They say there is no correlation between finding generic E. coli in the water and the presence of salmonella.
Irrigation is not the only way water can contaminate produce.
Water runoff can carry manure or animal feces from one farm to another. Growers often create buffer zones of unfarmed land to minimize the risk from neighboring animal farms. How much of a buffer should their fields have to be safe?
Scientists don’t know.
California’s LGMA requires that farms be at least 400 feet away from any sizable feeding operation. Florida’s regulations do not specify a distance, so growers are often subject to the requirements of their commercial customers, who may set stricter guidelines.
For the tomatoes it grows for Outback Steakhouse, Pacific Tomato Growers must make sure its fields are at least a half mile away from the nearest cow, according to Beau McHan, harvest manager for company’s East Coast operations.
“We’ve got some customers saying, ‘You’ve got to be a mile away from the nearest animal or were not going to buy from you,’” said David Gombas, senior vice president for food safety and technology at the United Fresh Produce Association. “Is there any science behind the mile? No. No more than there is over the 400 feet.”
Pest control also frustrates farmers. Fences can keep out deer and cattle, but not Canada geese, chickens, snakes, frogs and turtles – the most likely carriers of salmonella in the Mid-Atlantic region.
Impact of the Elements
Heavy rains exacerbate the problem in places such as Florida, where lizards, frogs and snakes may take cover under the canopy of tomato plants. Wire fencing can keep birds from eating crops, but it can’t keep those crops free of bird droppings.
“These pathogens are insidious. You can do everything right and still have a problem,” said Scott Horsfall, chief executive officer of the LGMA.
Amid the ambiguity, people know that without proper hygiene, workers can spread contamination. It’s a problem if workers in the fields don’t have access to restrooms.
Tomato Growers has developed portable restrooms and hand-washing stations that are built to avoid cross contamination. Fieldworkers wash their hands at one station and receive gloves at another. One worker’s sole responsibility is to keep the facilities clean by continuously wiping them down with chlorine. This worker also ensures that harvesters wash their hands before receiving new gloves.
But despite such measures, outbreaks still occur. And when they do, researchers often cannot find the pathogen responsible.
“The thing that we’re all stymied by is: Where does the salmonella hide? It’s so damn difficult to find in the environment,” said Chris Walsh, GAPs trainer for the Joint Institute for Food Safety and Applied Nutrition, a research and education partnership of the FDA and the University of Maryland. “How does it hide in the environment? Why can’t we find it? And then, why can it find us so easily when we eat it?”
When fresh produce is involved, the investigation is complicated by the product’s short shelf life – about 10 days. It takes at least two weeks for the CDC to link an illness to a specific outbreak. By the time an investigation begins, the culprit is likely long gone – either eaten or tossed.
The government has some tools to identify contaminated produce at its source.
Those include USDA’s Microbiological Data Program (MDP), which annually tests about 18,000 fresh produce samples – taken from distribution centers and terminal markets in 11 states – for E. coli O157:H7 and salmonella. The FDA also conducts tests, but on a much smaller scale: about 1,000 samples annually in 1999, 2001 and 2005.
MDP has triggered 20 recalls in the past two years, including a recall of grape tomatoes by Six L’s Packing Co., of Immokalee, Fla., in April.
The produce industry says the program, which was never intended to be a regulatory tool, is ineffective. Recalls are issued weeks after the affected produce likely was eaten, and growers say they are blamed for contamination that could have occurred long after produce left their fields.
Now the program is on the chopping block. In June the House passed a bill that would cut the $4.75 million testing program.
Even if salmonella is traced back to the farm, researchers say they rarely find the pathogen’s source.
“That’s one of the frustrating things about salmonella not showing up in the fields,” said Donna Pahl, a faculty extension assistant at the University of Maryland who is researching the bacterial counts of different water sources. “But then you have an outbreak. It has to be somewhere.”