The E. coli O157:H7 saga shows how the denizens of an animal's GI
tract find their way to our own digestive systems. This brings up a delicate
point, rarely discussed in polite company, but one central to the rest of this
chapter. Put simply, animal and human waste is the source of most foodborne
illness. And what we eat usually becomes contaminated long before it reaches us
-- during processing, at the slaughterhouse, or right on the farm.
Of course, that's a resonant theme in public health. The sanitary revolution of
the nineteenth century -- the discovery that the diseases of squalor and
overcrowding could be prevented with sewage removal and clean water -- was
occasioned by fear of cholera, typhoid fever, and other pestilential diseases.
Before this transformative event, daily life was unimaginably filthy.
"Thousands of tons of midden filth filled the receptacles, scores of tons lay
strewn about where the receptacles would receive no more," observed an English
medical officer in Leeds in 1866. "Hundreds of people, long unable to use the
privy because of the rising heap, were depositing on the floors."
Which is precisely how the animals that become our food live today. And why, at
the CDC, officials in the foodborne and diarrheal disease branch long for a
sanitary revolution: clean piped water and sewage disposal and treatment -- for
animals. Like the nineteenth century innovations that controlled typhoid fever,
animal sewage would be separated from the human food and water supply, and also
from the animal food and water supply. "It's a paradigm shift," says the
CDC's Fred Angulo. "Farmers don't consider themselves food handlers."
The site of modern meat production is akin to a walled medieval city, where
waste is tossed out the window, sewage runs down the street, and feed and
drinking water are routinely contaminated by fecal material. Each day, a
feedlot steer deposits 50 pounds of manure, as the animals crowd atop dark
mountains composed of their own feces. "Animals are living in medieval
conditions and we're living in the twenty-first century," says Robert Tauxe,
chief of the CDC's foodborne and diarrheal diseases branch. "Consumers have to
be aware that even though they bought their food from a lovely modern deli bar
or salad bar, it started out in the sixteen hundreds."
The feedlot is just the start of their fetid journey. At the head of the
slaughterhouse line, a "knocker" wields a pistol-like device to drive a metal
bolt into a steer's head. Other workers cut the animal's throat to drain blood,
and use machines to sever the animal's limbs, tear off its hide, pull out its
organs. More than 300 animals may pass through the line in an hour, each
carcass weighing 650 to 800 pounds. At the slaughterhouse, writes journalist
Eric Schlosser, "The hides are now removed by machine; but if a hide has not
been adequately cleaned first, pieces of dirt and manure may fall from it onto
the meat. Stomachs and intestines are still pulled out of cattle by hand; if
the job is not performed carefully, the contents of the digestive system" --
i.e., waste -- "may spill everywhere."
A United States Department of Agriculture study published in 2000 found that 50
percent of feedlot cattle being fattened for slaughter during the summer months
carried the E. coli O157:H7 bacterium in their intestines -- a far
higher figure than previous government estimates. Another study found that
about 43 percent of the skinned carcasses tested positive before being
eviscerated, suggesting that microbes were being spewed within the plant.
In early July 2000, the Excel Corporation -- the nation's second largest beef
processor -- allowed an Associated Press reporter to visit its huge Fort
Morgan, Colorado, meat packing plant. Asked about the dangers of tainted meat
reaching consumers, Excel's food safety director replied: "It's like a roll of
the dice or a game of Russian roulette." Two weeks later, the face of
three-year-old Brianna Kriefall, of South Milwaukee, appeared on front pages
across the country. She had died from eating a slice of watermelon at a Sizzler
restaurant. The watermelon had been sliced in the restaurant kitchen, on the
same countertop where a meat grinder was used to convert steak trimmings --
E. coli-contaminated steak trimmings -- into hamburger. The trimmings
came from sirloin meat packed in heavy vacuum-sealed bags. The bags had been
shipped just a few days earlier from Excel's Fort Morgan plant.
Chicken farming is just as noxious. But before delving into that, a word about
chickens: they're not all created equal. In the agribusiness world, there are
two kinds of chickens -- the broilers that give us meat, and the layers that
give us eggs -- and they are totally separate industries governed by different
practices, riddled with different problems, and even centered in different
parts of the country (the top broiler states are Georgia and Arkansas, while
the top egg-producing locales are Ohio and California).
First, a look at broilers. In her book Spoiled, journalist Nicols Fox
writes that "If chicken were tap water, the supply would be cut off." Oddly
enough, the government doesn't have hard numbers on Salmonella and
Campylobacter contamination rates, and what they do have is hardly
appealing. A 1999 study from the USDA's Agricultural Research Service, for
instance, found that 7 percent of chickens sampled at slaughterhouses had
Salmonella and 30 percent had Campylobacter -- but, as one
scientist there admitted, those numbers are probably low. For many years,
researchers assumed that clearing feces, rodents, and insects from the broiler
houses where the birds live out their five to nine weeks would solve the
problem. But new studies suggest that the source of chicken contamination may
be more deep-rooted. The 9.5 billion young broilers that Americans eat each
year are actually the fourth generation in a carefully husbanded line.
Scientists now believe it's the three previous generations -- the "breeders" --
that regularly pass down infection. When he tested birds at the top of the
pyramid -- the great-grandparent breeder flocks -- microbiologist Nelson Cox
at the USDA's Russell Research Center found that 36 percent were positive for
Salmonella. Cox suspects that these birds transmit pathogens to
subsequent generations by contaminating their own eggs with feces that carry
high levels of Salmonella, Campylobacter, Listeria, and Clostridium
perfringens. Because the hen's body temperature is quite warm -- between
104 and 107 degrees Fahrenheit -- she usually lays her egg on a day in which
the air is cooler than her body. That temperature gap forces bacteria on the
porous surface of the egg to get sucked into the membrane underneath, where
most organisms live contentedly while the fertile egg is incubating. When the
chick pecks its way out, it eats the pathogens. "The largest contributor to
contamination of a broiler flock," says Cox, "is the mother hen -- the feces of
the parent bird." That means the human disease on our end of the food chain
won't end until farmers either clean up the three generations above, or
scientists figure out how to snap the links of contamination. Vaccines may not
be the answer, since they are only effective against diseases that make
chickens sick -- and both Salmonella and Campylobacter are benign
commensals, living happily in the birds' intestinal tracts without causing
harm. Another possibility, slaughtering the priceless great-grandparent breeder
birds, would drastically raise chicken prices.
Now on to layers. Modern houses for egg production are avian megalopolises. In
1945 the typical henhouse sheltered 500 birds; today it can contain 80,000 to
175,000, with up to 20 houses in a single operation. (As in the livestock
industry, this huge scale is a result of industry consolidation; in 1996 there
were approximately 900 egg operations in the United States, compared to 10,000
in 1975.) Laying flocks stay in the same house for up to a year and a half,
which means that detritus builds up. "You have a lot of everything," says
Richard Gast, a microbiologist at the USDA's Southeast Poultry Research
Laboratory. "A lot of birds, a lot of manure, a lot of moisture, a lot of dust.
Everything that walked into that house -- every two- and four- and six-legged
creature -- is a potential vector for moving it around."
What spreads in this tenement is Salmonella enteritidis, or SE, the
villain behind most egg-related outbreaks. SE is a versatile bug, capable of
infecting birds through two different routes. One is orally, since chickens eat
feces. Another route -- more troubling, because scientists haven't figured out
how to interfere with it -- ascends through the cloaca, the cavity in birds
into which empties the products of both the intestinal and reproductive organs.
SE is sucked up into the bird's reproductive tract and eventually into the
ovaries. From there, it gets inside eggs even before the shell is laid down --
indeed, most eggs become systemically contaminated with Salmonella
enteritidis in this way. Just where SE came from, or why it spread
so suddenly in the 1980s, remains a mystery. Found in 1 of every 20,000 eggs,
SE makes French toast, Hollandaise sauce, and raw cookie dough risky culinary
excursions.
Animal waste and its dangerous microbes aren't confined to the farm, of course.
Manure -- spread through fertilizer, irrigation water, insecticide solutions,
dust, even wild birds and amphibians -- gets on produce too. Typical is an
outbreak that took place in 1998, when patrons of a Kentucky Fried Chicken
restaurant in Indianapolis became ill with E. coli O157:H7.
Zeroing in on KFC's cole slaw, investigators discovered that some of the
cabbage came from fields supplying a Texas vegetable company -- and that,
during a severe drought, the fields were flooded with untreated water from the
Rio Grande, where cattle had waded and relieved themselves in the irrigation
canals. Similarly, at Disney World in Orlando, Florida, thousands of visitors
from all over the country were believed to have been infected with
Salmonella in 1995 after drinking unpasteurized orange juice at special
"character breakfasts" at the park, in which costumed Disney characters mingle
with the guests. The orange juice came from a small processing plant nearby --
a plant where the walls and ceiling of the processing room had cracks and
holes, and where frogs congregated near the equipment. Outside the plant,
investigators found Salmonella in a toad, in tree frogs, in soil, and on
unwashed oranges. E. coli O157:H7 contaminates unpasteurized cider when
fallen apples touch cattle or deer waste and are then mixed with other pieces
of fruit. Numerous lettuce outbreaks have occurred after the heads were exposed
to cattle manure. Organic foods are hardly immune to these pitfalls. In fact,
microbiologists have found more bacterial contamination on organic than on
conventionally grown produce, and no one is quite sure how much composting it
takes to knock off pathogens in manure. That gap in knowledge has real-life
consequences. In rural Maine in 1992, a woman who abided by a lacto-vegetarian
diet, consisting almost exclusively of vegetables fertilized with manure from
her cow and calf, developed E. coli O157:H7 when she failed to wash the
vegetables well enough. Through improper handwashing, she passed the infection
on to three neighborhood children, one of whom, a three-year-old boy, died of
kidney failure.
Farm conditions create a wide-open channel down which emerging pathogens travel
from food animals and produce to people, and the modern food industry has
converted a two-lane country road into a 12-lane interstate. "Salmonellosis is
rare in developing countries, where sanitation is poor and diarrheal diseases
are endemic, but where food production and consumption are local," writes
Martin Blaser, chairman of the department of medicine at New York University,
in the New England Journal of Medicine. Blaser's dispiriting conclusion?
"Salmonellosis -- with the notable exception of typhoid fever -- is a disease
of civilization. "
And outbreaks are not so much "point source" as pointillist. Changes in
agriculture and food manufacture -- vaster and fewer farms, slaughter plants,
and processing facilities -- have given pathogens a larger stage on which to
strut. In this miraculous food economy of scale, when things go wrong, they go
wrong in a big way. Mass-distributed items with spotty or low-level
contamination are consumed by people living far from the source. This leads to
a new, insidious kind of epidemic: one with low attack rates (less than 5
percent of the people who eat the contaminated food) but huge numbers of
dispersed victims. Take the massive 1994 outbreak of Salmonella enteritidis.
Usually, SE is linked to undercooked eggs or egg products. But Schwan's ice
cream, made in Minnesota and delivered to homes in all 48 contiguous states,
was made from premix that had been transported to the plant in tanker trailers
-- trailers that had previously carried unpasteurized liquid eggs. Though the
insides of the tankers were supposed to be washed and sanitized after hauling
eggs, drivers sometimes skipped that laborious step. Across the country, an
estimated 224,000 ice cream aficionados -- mostly kids -- paid the price in the
largest outbreak of salrnonellosis ever recorded from a single food source.
home + industrial meat + interviews + the politics of meat + is your meat safe? + the inspection system
inside the slaughterhouse + producer chat + introduction + discussion + video
tapes & transcripts + press reaction + credits + privacy policy
FRONTLINE + wgbh + pbsi
web site copyright WGBH educational foundation
| |
