Produce Problems: How Pigs, Pollution And Other People Taint Our Fruits And Veggies
The second in a series investigating the complex linkages between human, animal and environmental health: The Infection Loop.
Ashley Armstrong's parents haven't let her eat green salad in five years.
While other parents struggle to get assorted greens into their children's bellies, the Armstrongs have left salad off Ashley's plate since September 2006, when the E. coli from a bag of spinach nearly killed her. Then 2 years old, Ashley was left with just 10 percent kidney function.
"We were totally naive," says her mother, Elizabeth, who now serves on the board of the Center for Foodborne Illness Research and Prevention, a public health advocacy group. "We assumed that the food we bought at our grocery store was safe. We assumed that the FDA, or whomever, had checked to make sure it was safe. We've since found out that's not the case."
Inspectors failed to pinpoint the exact source of the E. coli outbreak that killed three people, sickened 205 and cost the spinach industry $100 million. About a mile from one contaminated spinach field, however, they found a wide range of suspects: high levels of the bacterium in free-range angus cows and their dung, and its genetic match turned up in local feral pigs, soil and surface water.
"There were so many different possible sources that we couldn't say for sure how the spinach got contaminated," Michele Jay-Russell, a food safety specialist at the University of California, Davis, told HuffPost. "But it raised awareness that cattle and wildlife intruding into the field or waterways could be risks for moving pathogens into the produce environment."
As far as Elizabeth Armstrong was concerned, all that mattered was that "somehow poop got in the plant."
It wasn't an isolated incident. Foodborne pathogens strike roughly one in six Americans every year, sickening 48 million, hospitalizing 128,000 and killing 3,000, according to the U.S. Centers for Disease Control and Prevention.
And choosing local and organic options, even going vegan, isn't enough to guarantee safety. Between 1998 and 2007, produce sickened almost 27,000 Americans in the course of nearly 700 foodborne illness outbreaks, according to the Center for Science in the Public Interest. The nonprofit group suggests that produce outbreaks now surpass the number of outbreaks originating in poultry, beef, pork or eggs.
In their wake, these waves of outbreaks helped prompt the U.S. government to implement new regulations, including some standards specific to produce safety.
Contaminated fruits and vegetables tend to be those that grow closest to the ground -- bean sprouts, lettuce and the like -- as evidenced recently by the suspected contamination of California romaine lettuce via manure-laden lagoons and of Oregon strawberries from deer feces.
Now, America's most deadly known foodborne-illness outbreak in more than a quarter-century has added a new danger to the list: cantaloupe contaminated by the bacterial infection listeria. Since the end of July, at least 28 people have been killed and 133 sickened after eating cantaloupe grown at Jensen Farms in southeastern Colorado. (An average produce outbreak can be linked to 39 illnesses, according to the Center for Science in the Public Interest.)
"We have rarely, if ever, seen this pathogen in produce," says Sandra Eskin, director of the food safety campaign with the Pew Charitable Trusts. This outbreak marks the first documented case of listeria in cantaloupe.
Only since the 1990s has produce emerged as an "important vehicle of transmission," says Jay-Russell, noting the heightened attention after the 1996 outbreak of E. coli in Odwalla unpasteurized apple juice.
One of produce's problems is that people tend to eat it raw, and therefore it misses a "kill step" such as heating or cooking. Jay-Russell says that means that oversight has to focus on the entire "food continuum, from the fields to the fork."
In Centennial, Colo., Jeni Exley, her husband and their college-age daughter ate cantaloupe from Jensen Farms with no ill effects. In nearby Littleton, however, Jeni's 84-year-old father, Herb Stevens, was not so lucky.
Before his bout with listeria, Stevens was independent. Since battling the infection, with its attendant fever, muscle aches, diarrhea and other symptoms, he requires daily nursing care and a walker.
Stevens and his wife hadn't worried about their cantaloupes. The elderly couple always bought by the half: not so much that they'd have to throw any leftovers away; cut open to offer a sneak peek inside. But listeria is invisible to the naked eye and easily transferred by knife from the rough, contaminant-inviting surface into the flesh. Once inside, the fruit's low acidity further encourages the bacteria's growth.
According to a federal report released last Wednesday, the Food and Drug Administration, the state of Colorado and Jensen Farms narrowed the listeria outbreak's root cause down to poor sanitation inside a packing facility used by the farm. Tests by the investigators, including experts in agriculture, veterinary medicine and environmental health, ruled out contamination in the farms' fields and irrigation systems, as well as any links to adjacent land use or animal intrusions.
Any of these pathways were reasonably suspect in this case, given listeria's widespread presence in the environment. Research led by Martin Wiedmann, a food science expert at Cornell University, found the pathogen in samples collected throughout New York state -- from sidewalks, parks, ponds, rivers, even the middle of state parks. Another study found that farmers brought listeria home on their clothing and shoes. To a lesser extent, listeria even landed in nonagricultural homes.
The pathogen is persistent, even hardy, withstanding cold temperatures and showing an ability to survive more than a decade indoors. "Bacteria are always trying to be one step ahead of us," says Jay-Russell of UC Davis.
Fortunately, as pervasive and aggressively adaptive as it is, listeria is typically only dangerous on the order of billions of cells, Cornell's Wiedmann said. And only certain subtypes, such as the monocytogenes strain identified on the cantaloupes, repeatedly appear in human outbreaks.
Jensen Farms adhered to safe practices in their melon production operations, such as the use of drip irrigation and plastic mulch to keep cantaloupe from resting directly on the soil, according to Michael Bartolo, a senior research scientist at the Arkansas Valley Research Center in Rocky Ford, Colo. However, there was still plenty of room for contamination.
On Wednesday's media call, Sherry McGarry of the CDC described a few likely culprits in Jensen's packing facility. The building's poor design allowed water to pool on the floor, and the lack of a pre-cooling procedure may likewise have helped incubate bacteria in condensation on melons moving from the warm outdoor air to cold storage.
Of course, that first microbe had to come from somewhere. McGarry suggested that low levels of listeria may have originally been present in the fields and subsequently been carried inside. A truck used to haul culled cantaloupe to a cattle operation was also parked adjacent to the packing facility, suggesting that feces may have hitched a ride.
"The investigation is still open," says McGarry. "There may be details that we are unable to provide at this time."
THE FOUR W'S
A wide range of human and environmental factors can in fact open the door for listeria, E. coli, salmonella and another foodborne pathogens to invade the human body. Eskin points to four general categories that account for most foodborne illness outbreaks: water, waste, wildlife and workers.
Pathogens don't live well on produce that is exposed to the sun and hot temperatures -- unless there's lots of water around.
In the wake of Tropical Storm Irene, Vermont farmers are tossing out perfectly good-looking potatoes and winter squash. The farmers know that if floodwaters come in contact with the edible parts of plants, there is danger of contamination from overflowing septic systems, wastewater treatment plants or soils laden with feces from dogs, deer or cattle. Even planting seeds during or after a flood can be risky.
Those factors are all key to pathogen development and spread, but scientists see one consistent starting point. "It's safe to say that most pathogens that make humans sick begin in the gut of an animal," says Pew's Eskin.
Many animals harbor and deposit microbes that are harmful to humans, but not always to the animal itself, explains Michael Doyle, director of the Center for Food Safety at the University of Georgia. From an animal's intestinal tract, the toxins can travel into feces and then onto an agricultural field through grazing, water irrigation or as fertilizer.
Close proximity between crops and cattle, especially if the grazing cattle are upslope of a field, may be particularly dangerous for produce. In 1985, the first reported outbreak connecting listeriosis to food was traced back to sheep that grazed in the vicinity of a cabbage field harvested for coleslaw.
Wild animals poop, too. "We don't grow food in a sterile environment or in a bubble. It's outside in the dirt," says Jeffrey LeJeune, a professor of food science, environmental and animal health at The Ohio State University. "If a bird flies overhead and decides that it's had enough to eat, it could leave a deposit on a melon or a tomato."
Fences can be helpful, but such restrictions on wildlife movement are controversial among ecologists. Jay-Russell suggests other approaches that have been adopted by many California growers, such as avoiding planting where there is a major wildlife corridor and walking the fields before harvest.
Other species aren't always responsible for contamination. Human waste, a likely contributor to this year's bean sprout E. coli outbreak in Germany, is also a consistent threat to the food supply. Produce can be at risk if a single worker doesn't wash his or her hands thoroughly.
"How many people touch a cantaloupe between the farm and table? A whole lot more than the number of armadillos that do," LeJeune says. "If we could solve all the problems of all of the animals, the problem wouldn't go away."