Health/Science

A chain of weak links on spinach

The system's set up to maximize profits at every level, not to ensure safety or to forestall health threats

BY DR MARC SIEGEL. Dr. Marc Siegel is an associate professor of medicine at the New York University School of Medicine. He is the author of "False Alarm: The Truth About the Epidemic of Fear."

September 25, 2006

The current outbreak in spinach of Escherichia coli 0157:H7 that's scaring my patients didn't occur in a vacuum. It is part of a culture of dealing with animals, plants and food that allows the spread of harmful bacteria.

There is a chain of events that occurs from cow to manure to contaminated water to crops to food that eludes regulation. Farmers concentrate on beefing up their cattle or maximizing their milk without sufficient regard to collateral damage from contagion. There is a crucial gap between U.S. Department of Agriculture supervision of animals and plants and Food and Drug Administration efforts by the time a product is labeled as food.

Outbreaks occur mainly because those monitoring each link in the chain of infection are not paying attention to the next link.

Cattle farmers are not thinking of the harmful effects of manure; they are concerned about selling their product. Sellers of organic fertilizer made from manure are hoping their product will grow vegetables, not concerned that it will contaminate water or spinach. Salad makers screen and cleanse their food but can't always afford the expensive equipment to detect the most elusive bacteria. There is also not enough separation between animal and animal products before they become human food.

Multiple studies in the agricultural literature have shown that dairy cows shed harmful bacteria at variable rates. This shedding is dependent on several factors that could be controlled, including the animal's feed. Studies have shown that changing feed from grain to hay decreases the acidity in the gut of cows that allows bacteria to thrive. Because very small amounts of 0157:H7 can cause human infection and because shedding of the bacteria by cows is so variable, proper surveillance of manure is also crucial in preventing outbreaks. But sophisticated laboratory techniques that are most effective at detection are very expensive and not commonly used. Current agricultural attempts to contain manure and organic fertilizers at the farm are not sufficient to prevent occasional seepage into water supplies, which sparks outbreaks.

Once an outbreak occurs in humans, the FDA is forced to play catch-up, in this case by putting an umbrella advisory over all spinach that sends the inadvertent message that the disease is much more widespread than it is. Because food is processed and packaged in one state and then mixed and sold across several states, containment and control become more difficult.

E. coli 0157:H7 is a strain that produces a toxin that breaks down the lining of blood vessels, causing bloody diarrhea in humans and sometimes kidney failure. Because cows lack the receptor on their cells to absorb the toxin, they don't show symptoms that they are carriers of the bacteria.

Before the current outbreak, there were close to 20 outbreaks linked to salad since 1995 in which the crops were fed water contaminated with E.coli from manure.

By feeding cows antibiotics, our meat industry promotes drug resistance and helps create genetically altered superbugs that can then be passed to produce as fertilizer. The current strain of E. coli that has caused the outbreak appears to be very virulent, making people sicker in dozens of states and causing more kidney failure than is usual for this strain.

A greater degree of vigilance and a new system of coordinated prevention and regulation are necessary to help prevent outbreaks. Studies also have shown that sodium chlorate as well as "pro-biotic" bacteria fed to cows - besides feeding them hay - may help to decrease the prevalence of this deadly strain. Feeding cattle antibiotics is a practice that should be banned.

Beyond the cow, it would help if there were more preventive measures in place on farms, especially in California. Since 1995, nine of the outbreaks in lettuce or spinach have been traced to the Salinas Valley. Currently, state investigators there are still trying to trace the outbreak to specific equipment in the salad factories, belatedly backtracking the spread from Natural Selection Foods out to other salad makers.

This outbreak is best understood by seeing it in perspective. Media-driven fear can cause us to wrongly perceive all salad as unsafe. But this fear also can serve as an important wake-up call.

As a physician, I am very aware of the bacteria or viruses a dog or cat harbors that can infect my patients during a bite. I know how to treat them, but, more important, health agencies are geared to prevent these infections through pet-control programs.

We need the same kind of comprehensive approach when it comes to animal management and food safety. Food safety needs to be better regulated with a more integrated prevention-oriented system involving the Agriculture Department, FDA and a new food safety agency to bridge the gap.

Dr. Marc Siegel is an associate professor of medicine at the New York University School of Medicine. He is the author of "False Alarm: The Truth About the Epidemic of Fear."
 

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Copyright © 1990-2007 Marc K. Siegel, M.D.