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kills the worm and its oocysts. For these and
other reasons that cooks in well-developed
countries need no longer worry about trichinellosis
from pork, see Misconceptions About Pork,
page 179.
The common fretting about trichinella is
a symptom of an enduring problem with the
transmission of all kinds of food safety information
from health professionals to the public: it’s
not getting where it needs to. While millions of
cooks in restaurants and homes overcook their
pork with almost religious zeal, few have ever
heard of the noroviruses that, through food,
sicken nine million Americans every year.
Overemphasis on the wrong pathogen also
occurs with botulisma foodborne disease that
strikes fear into the hearts of cooks everywhere.
The CDC study mentioned earlier estimates that
a mere 58 cases a year of botulism occur in the
U.S., causing four deaths. Any death is tragic, of
course, but one needs to place the numbers in
perspective; more than 20 times as many people
die every year in the U.S. from hornet, wasp, or
bee stings (82 in 2005).
Meanwhile, Toxoplasma gondii, a protist
primarily found in the feces of pet cats, sickens
112,500 people a year, killing 375 of them and
thus claiming nearly 100 times as many victims
as botulism does. Indeed, toxoplasma is the
primary reason that protists command such a fat
slice of the pie chart on page 113T. gondii
alone accounts for 98% of all protist-related
fatalities. Toxoplasma may cause schizophrenia
and other psychological damage as well (see
page 126).
Annual mortality rates in the U.S. from:
Not all microbial infamy is undeserved, of
course. Salmonella really is as dangerous as most
people imagine. But here, too, confusion reigns
over the true source of contamination.
Salmonella bacteria do not live in chicken meat
(muscle tissue), the source most commonly
fingered as the culprit. Instead, the bacteria
normally live in the intestinal tracts and feces of
chickens and can contaminate the meat during
slaughter and processing (except S. enteritidis,
which can infect hen ovaries and contaminate
intact eggs regardless of fecal contact).
The poultry industry has made enormous
strides in containing contamination, and chickens
are far from alone in spreading the disease. In
2008, for instance, U.S. investigators traced
a major outbreak of salmonellosis to tainted
peanut butter and other peanut-containing foods.
Investigations of the sources of other recent contagions
have implicated hot peppers and tomatoes.
Similar misinformation underlies an even
broader food-related safety belief. The public tends
to view meat, fish, and poultry as being more
suspect than fruits and vegetables, particularly
with regard to the frequency of contamination by
bacterial pathogens like Salmonella species and
E. coli O157:H7. Yet this is emphatically not so.
What matters most are the specific ways foods
are handled. Because bacterial foodborne illness
generally results from exposure to feces, it follows
that agents such as E. coli O157:H7 can contaminate
any food.
E. coli does infect cattle and is found in their
feces, but meat-packing plants have worked hard
to avoid contamination in the slaughterhouse, and
widespread outbreaks have been relatively rare in
recent years. Investigators, in fact, traced the
largest recent outbreak of E. coli infections in the
United States to contaminated baby spinach.
The 2006 episode led to 205 confirmed illnesses,
three deaths, and a tentative link to wild
boars living in the coastal mountains of California.
Epidemiologists discovered that the boars had
become infected with E. coli O157:H7, probably by
consuming the feces of infected cattle. The boars
presumably passed on the bacterial contamination
when they defecated in spinach fields. The harvested
spinach was washed, but this seems to have
simply diluted and spread the contamination from
a few isolated samples to the entire output of the
processing plant.
THE ETYMOLOGY OF
Disease Names
Just as biologists follow naming conventions for pathogens,
medical professionals have developed a method of naming
diseases. Several different approaches are used, which can
make things confusing to the uninitiated.
One common convention is to append “-osis” or “-asis” to
the root of the pathogen’s genus. An infection with Trichinella
spp. therefore becomes trichinellosis. Medical authorities
sometimes modify this straightforward method to yield
less obvious derivatives. Thus, infection with the protist
Previous outbreaks of E. coli infections in the
U.S. have involved strawberries, lettuce, and other
produce. Meat, particularly ground beef, also has
been implicated, but the common assumption that
E. coli contamination is primarily a problem with
meat doesn’t square with the facts.
Why do trichinella and botulism evoke such
paranoia while toxoplasma and noroviruses are
virtually ignored? Why do so many people
disregard the most common and easily thwarted
sources of contamination from foodborne bacteria?
It seems clear that people don’t know all that
they should about the true distribution and traits
of parasitic worms, protists, bacteria, viruses, and
other food pathogens. We hope the rest of this
chapter sheds some light on the subject.
Strawberries, spinach, and peanut butter
are just as likely to harbor foodborne
pathogens as meat, fish, and poultry are.
Most recent outbreaks of foodborne
illness have, in fact, been linked to fruits,
vegetables, and nuts.
Entamoeba histolytica is called amebiasis.
When the pathogen is unknown or ill-defined, medical
researchers may name a disease or condition after its symptoms.
The term gastroenteritis, for example, describes an
acute infection of the gastrointestinal system without specifying
the responsible pathogen.
Finally, doctors refer to some diseases or disease conditions
by ad hoc names, bowing to popular usage or medical tradition.
Botulism and strep throat are all well-known examples.
Traffic Accidents:
one in 6,500
Foodborne Toxoplasmosis:
one in 728,000
Hornet, Wasp, and Bee Stings:
one in 3.6 million
Foodborne Botulism:
one in 68 million
118 VOLUME 1 · HISTORY AND FUNDAMENTALS
MICROBIOLOGY FOR COOKS 119