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<h1 class="css-19v093x">Industrial Hog Farms Are
Breeding the Next Pandemic</h1>
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<div class="css-7kp13n">By</div>
<div class="css-7ol5x1"><span class="css-1q5ec3n">Tom
Philpott</span></div>
<div class="css-8rl9b7">motherjones.com</div>
<div class="css-zskk6u">14 min</div>
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<p><span>In March of 2009,</span> people
in the rural Mexican village of La
Gloria started coming down with a
nasty respiratory infection. The town,
located in the state of Veracruz, sat
5 miles from an industrial-scale hog
farm. Within a few weeks, clusters of
this rapidly progressing pneumonia
arose among Mexico City residents.
Researchers soon identified the bug as
a “novel swine flu.” It quickly jumped
to the United States and spread
worldwide, and in June, the World
Health Organization declared a
pandemic, the first time it had done
so since the deadly avian flu outbreak
of 1968.</p>
<p>The 2009 swine flu strain didn’t turn
out to be as deadly as originally
feared. Although indeed novel, it was
similar enough to older flu strains
that about a third of people over
60—the most vulnerable population—had
preexisting antibodies to the virus,
helping them shake it off. Even so, it
killed more than 284,000 people around
the world, including at least 12,469
Americans.</p>
<p>We might not be so lucky next time.
As the COVID-19 crisis lingers with no
end in sight, it’s no fun to think
about other emerging contagions that
could be coming our way. But given the
gaping holes the coronavirus fiasco
has exposed in our infectious-disease
response systems, it seems prudent to
squarely face what’s coming down the
pike—in hopes we can prepare to do
better. </p>
<p>The likely source of the next
pandemic is all around us: It’s the
same one that triggered the 2009
scare. Industrial-scale hog and
chicken farming—innovated in the
United States and rapidly spreading
globally—provides an ideal environment
for the evolution and transmission of
novel pathogens, especially influenza,
that can infect people. (Cattle
generally aren’t susceptible to
human-adapted flus.) </p>
<p>“Another influenza pandemic occurring
at some stage of the future is
exceedingly high,” said Richard Webby,
professor of infectious diseases at
Memphis-based St. Jude Children’s
Research Hospital and director of the
World Health Organization’s
Collaborating Center for Studies on
the Ecology of Influenza in Animals.
“The chances that it’ll come from some
sort of farmed animal—my personal
opinion is, that’s high as well.” </p>
<p>Gregory Gray, a professor of
medicine, global health, and
environmental health at Duke
University and an expert on
animal-to-human disease transmission,
is even more direct. His biggest worry
for the next viral pandemic?
“Influenza A viruses that originate in
pigs,” he said. “Hands down.” </p>
<p>The 2009 flu scare inspired the US
government to ramp up its effort to
monitor factory-scale farms for new
pathogens, Gray added. But its
surveillance was limited from the
start, and in recent years has
dwindled. </p>
<p><span>Pigs have a special </span>
capacity to incubate new viruses.
Although birds are hosts to many kinds
of influenza, avian flus don’t bounce
easily to humans. There have been some
exceptions: The 1997 H5N1 outbreak in
Hong Kong sickened at least 18 people
and killed six. But that event, as
well as smaller outbreaks since, was
relatively easy to control, because
once the pathogen invaded the human
immune system, it didn’t show much
ability to spread person-to-person.
Most infections involved people who
had been in direct contact with birds.</p>
<p>Hogs are different. While pure swine
flus don’t jump easily to humans, pigs
can catch flu viruses that are from
birds and humans, and then pass them
back and forth. When more than one flu
virus has infected a single host, the
viruses have the sinister ability to
swap genes, a process researchers call
“reassortment.” Like DJs creating
something new by grabbing and
combining snippets from old vinyl
records, flus use the bodies of pigs
to make the viral equivalent of a
mixtape. If a pig catches an avian flu
and a human flu at the same time, the
two viruses can morph into novel
strains that contain swine, human, and
avian genetic material, with the
potential ability to infect all three
species.</p>
<p>That’s why many epidemiologists call
“mixing vessels” for flu strains; they
provide a host in which avian- and
swine-evolved flus can reach people.
And since human immune systems have
little exposure to bird flus, it can
be quite dangerous for us when genetic
traces of these bird flus invade our
bodies through a strain that was
reassorted inside of a hog. </p>
<p>So scientists were alarmed earlier
this summer when Chinese researchers
published a paper in the peer-reviewed
US journal <em>PNAS</em> reporting
that<strong> </strong>an “avian-like”
swine flu strain had become pervasive
in the nation’s vast hog operations,
containing “all the essential
hallmarks” of a virus that can cause a
human pandemic. The team tested 338
workers who routinely come into
contact hogs and found that 10.4
percent had antibodies to the new
strain, meaning they had unknowingly
contracted and recovered from the
virus. They also tested 230 people who
aren’t associated with the hog
industry and found antibodies in 4.4
percent of them. In other words, the
virus is out there, infecting people
and evolving; likely being swapped
back and forth between workers and
hogs. </p>
<p>The strain recently identified in
China, known as G4 EA H1N1, is related
to the H1N1 flu that caused the global
pandemic in 2009. The 2009 strain
contained genes from avian, swine, and
human flus—a classic “triple
reassortment.” It has also taken on
avian genes through reassortment that
makes it novel to our immune
systems—meaning it could be very hard
to fight. </p>
<p>The new flu hasn’t caused major
problems yet; it hasn’t proven either
highly contagious or particularly
virulent. But that could change as it
circulates among the workers and
animals in China’s hog industry. The
fact that it’s out in the world, the
paper warns, “greatly enhances the
opportunity for virus adaptation in
humans and raises concerns for the
possible generation of pandemic
viruses.” The WHO’s Webby put it like
this: “It’s a numbers game. These
viruses throw out mutations every time
they replicate, so the more chances
the virus gets, the more interactions
with humans, the more chance that one
day the stars will align in the right
order, the virus will get the right
mutation, and take off.” </p>
<p><span>Changes in our </span> eating
habits and farming practices have
dramatically ramped up pigs’
propensity to gin up new pathogens.
Humans domesticated them at least
9,000 years ago, and we’ve probably
been swapping flus with them ever
since. But for almost that entire
history, hog farming was essentially a
backyard activity, with relatively few
animals per operation, and broad
genetic diversity in the population.
The numbers game Webby describes
exists when hogs are kept on a small
scale, outdoors, with the herds
largely isolated from each other. But
what’s happening now is different.</p>
<p>Starting in the 1980s, US pork
packers began to change their model,
inspired by what the poultry industry
had done decades before. Instead of
buying hogs from small producers,
meatpacking companies moved to a
vertically integrated model, pushing
to source their pigs from large,
confined operations working under
production contracts.</p>
<p>The shift turned the industry upside
down. According to US Census of
Agriculture figures, in 1982, 330,000
farms raised 55.4 million hogs. By
2017, just 66,000 farms were churning
out more than 72 million pigs. In
other words, 80 percent of US hog
farms exited the business over that
period even as total output jumped 21
percent—and so the average number of
hogs per farm spiked from 168 to
2,000, a 12-fold increase. And that
figure understates the scale of modern
hog production. The 2017 Ag Census
show that three-quarters of US hogs
are raised on the 3,600 largest
operations, each averaging more than
14,000 animals.</p>
<p>Today, an industrial-scale hog “barn”
is an enclosed facility holding as
many as 4,440 pigs. A typical
operation consists of several of these
buildings clumped together, each with
ventilation systems that has the
potential to suck up airborne flu
pathogens from each barn and pass them
to the barn next door. </p>
<p>China’s pork sector, the globe’s
largest, is rapidly mimicking the US
model, though it’s at an earlier stage
of the trajectory. Between 1975 and
2013, growth in China’s pork
consumption rose by a factor of eight.
(Though this growth has flattened in
recent years.) Giant factory
facilities took the place of the
micro-scale operations that had
sustained the region for centuries. In
2000, 74 percent of Chinese pork
production came from backyard farms.
By 2015, household sources were
providing just 27 percent of the
nation’s domestic pork. The
contribution from commercial farms
with at least 1,000 hogs, meanwhile,
tripled over that decade.</p>
<p>What could possibly go wrong? Rob
Wallace, an evolutionary biologist
with the Agroecology and Rural
Economics Research Corps and author of
<em>Big Farms Make Big Flu</em>,
argues that the industrial animal
farming model delivers a perfect
habitat for flus to proliferate,
evolve, mutate, and adapt—to
essentially hack the numbers game for
creating pandemic strains.
Factory-scale farms provide a huge
playground for human and avian flus to
“trade multiple combinations of
genetic segments,” he said. They’re
“an explosive evolutionary
accelerant.”</p>
<p>For most of the 20th century, the
flus circulating among US pigs didn’t
evolve much genetically, meaning our
immune systems had plenty of time to
adapt the ability to fight them off.
It wasn’t until the 1990s—when the
consolidation of US hog production was
reaching a crescendo—that pig flus
began to reassort wildly with human
and avian flus and create new strains
that can jump to people. In a
prescient paper he co-authored with
other researchers, published five
years before the 2009 outbreak, the
WHO’s Webby sounded the alarm. “The
influenza reservoir in the United
States swine population has thus gone
from a stable single viral lineage” to
a “dynamic viral reservoir containing
multiple viral lineages,” making the
US swine population an “increasingly
important reservoir of viruses with
human pandemic potential,” they wrote.
</p>
<p>In addition to capitalizing on the
sheer number of potential hosts
breathing in each other’s exhalations
and excretions in a modern hog
facility, viruses also take advantage
of the pigs’ genetic similarity. With
a genetically diverse drove, some pigs
will have a mutation in their immune
systems that blocks infection,
limiting the pathogen’s range. But “if
you’ve got a couple thousand
genetically similar hogs packed in a
barn, then it’s all food for flu,”
Wallace said. As the industry breeds
hogs to deliver consistent, uniform
pork products, the genetic diversity
of hog populations erodes, and what
Wallace calls an “important firewall”
to developing pandemic flu strains
crumbles.</p>
<p>The workers who tend these pigs are
prime targets for moving the virus
into surrounding communities. And
global trade ensures that the flu can
travel the world. “The United States
and Canada, the largest exporters of
hog, are also the largest exporters of
swine flu,” Wallace said. After the
North American Free Trade Agreement of
1994, Mexico began to dramatically
scale up its own hog sector, leaning
heavily on hogs imported from the
United States and Europe. That flow of
hogs and their attendant flus is the
likely source of the 2009
triple-assorted pandemic strain, a
2016 analysis by US, Mexican, and
European researchers shows. Wallace
also points to a 2015 <em>Nature</em>
study by a global team led by US
National Institutes of Health
researchers with a chart showing how
flu bugs circulating on US farms
disperse globally: </p>
<div class="RIL_IMG" id="RIL_IMG_2">
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alt=""> </figure>
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<p><span>The US pork industry,</span>
for its part, asserts that the workers
who tend hogs are unlikely to swap
viruses with them, because hog farmers
follow stringent biosecurity measures.
“Modern US pig barns are designed
specifically for pig health and
safety,” Jason Menke, director of
marketing communications for the
National Pork Board, wrote in an
email. Farmers wear special boots and
clothing that stay in the barn. Many
farms require caretakers to shower in
special facilities attached to the
barn, which “minimizes the chance that
the pigs will be exposed to a pathogen
that will make them ill.” Workers are
also “encouraged” to wear
personal-protective gear like masks to
“protect themselves from both illness
and injury working on the farm,” Menke
wrote. He added that “sick leave
policies encourage workers to stay
home when ill to prevent unnecessarily
exposure to other workers on site or
to the pigs, since pigs can be
infected with human influenza
strains.”</p>
<p>But no biosecurity system is perfect,
Wallace counters. In a 2015 paper
looking at flu strains circulating on
US pig farms, the National Institutes
of Health and US Department of
Agriculture researchers found that,
despite the industry’s biosecurity
efforts after the 2009 H1N1 pandemic,
industry workers “continuously” kept
reinfecting the US hog herd with their
flus. That meant hogs, mixing vessels
for human and bird flus, got a steady
infusions of human-adapted flus, free
to re-assort and create novel strains
that can infect people. </p>
<p>Wallace thinks that factory-scale
livestock farming inherently generates
viral pandemic threat, and should thus
be dismantled—a view that gained
political traction late last year when
Sen. Cory Booker (D-N.J.) floated a
bill that would do just that. Booker’s
proposal, which has since gained
support from Sen. Elizabeth Warren
(D-Mass.) and Rep. Ro Khanna
(D-Calif.), remains unlikely to pass;
the meat industry remains a powerful
lobbying force in Washington. But as
Ezra Klein recently reported in <em>Vox</em>,
an “odd-bedfellows coalition” of
animal-rights activists, economic
populists, and small-scale farmers is
rallying around it. </p>
<p>Mainstream university-based flu
researchers are far more cautious
about challenging the industry so
directly. While Duke’s Gray insisted
that the next pandemic might come from
hogs, he does not advocate for banning
industrial hog farming. “We have some
of the safest and lowest-cost pork
production in the world, and that’s
wonderful,” he said. “And we are
exporting that technology to many
places around the<strong> </strong>world
and they’re all shifting to
large-scale farming—it’s the way to go
to keep the hogs safe and produce low
cost meat.”</p>
<p>He adds, however, that the pork
industry and the US Department of
Agriculture—which regulates the safety
of meat production—aren’t doing enough
to monitor the viral pathogens that
can flourish on large hog operations.
Through surveillance, researchers can
see what’s out there and kick-start
the development of human vaccines when
novel strains emerge. </p>
<p>Back in 2010, in response to the
previous year’s pandemic, the Animal
and Plant Health Inspection Service
(APHIS), a division of the US
Department of Agriculture, launched a
program to monitor and analyze flus
circulating in the hog population.
It’s an important but limited effort,
Gray said. It relies on hog producers
and veterinarians to swab animals
showing flu symptoms (coughing,
sneezing, runny nose, etc.) and send
them in to USDA-affiliated labs. Gray
characterized the program as “<span>very
spotty” because of its focus on
“passive” testing, which relies on
farmers to volunteer samples from
sick animals. </span></p>
<p><span>Active testing, on the other
hand, would randomly select samples
from both visibly sick and
asymptomatic animals. “T</span><span>here
are influenza viruses that infect
both humans and pigs [but] do not
necessarily cause signs of infection
in both,” he said. Similar to how
people can be infected with COVID-19
and spread it without showing
symptoms, pig flu often hides in
animals that appear healthy. “</span><span>Hence,
I have long argued that passive
surveillance among only sick pigs
has the potential to miss novel
emerging swine influenza viruses
that may harm humans.” <br>
</span></p>
<p><span>The US hog industry is “really
good” at detecting and preventing
the spread of diseases that make
pigs sick and lower production, Gray
says. But viruses that don’t
directly harm hogs—including those
that might do worse damage to
humans—”are tolerated, permitted to
spread and to mutate.”</span></p>
<p>Worse still, Gray adds, as the 2009
flu pandemic recedes into the past,
funding for the APHIS surveillance
program—and the participation of hog
farmers—has dwindled. In the agency’s
most recent report on the program,
released in July 2020, total samples
received from farmers peaked in 2015
at 35,792 and had fallen to 3,098 in
2019. An APHIS spokesperson attributed
the drop to changes made in 2016 to
shift costs from the USDA budget on to
hog farmers. </p>
<p><span>Meanwhile, influenzas aren’t</span>
the only viruses that circulate on hog
farms. Coronaviruses do, too—like the
porcine epidemic diarrhea virus, which
killed 10 percent of US hogs in
2013-14. (PEDV does not infect
humans). As for SARS-CoV-2, the
coronavirus causing the current
COVID-19 pandemic, a study released in
June by Chinese researchers found that
pigs are at least theoretically
susceptible: They have lung and kidney
cells that can be invaded by this
particular pathogen. But laboratory
attempts to infect pigs with it have
so far not succeeded. “Given that the
COVID-19 pandemic is still progressing
and SARS-CoV-2 strains are constantly
evolving,” they wrote, “we need to
keep monitoring and evaluating the
possibility of pigs to become
intermediate hosts” of the pathogen.</p>
<p>Gray finds the prospect of
hog-adapted SARS-CoV-2 daunting. As
they do for flu, pigs could emerge as
what disease researchers call a
“reservoir” for the pathogen—a large
host population that keeps the
pathogen circulating, giving it more
opportunity to infect people. “My
chief concern is that the current
SARS-CoV-2 virus adapts to commercial
hogs, becomes amplified in them, and
cause<strong>s</strong> widespread
infections, increasing the risk of the
virus moving from the pigs to infect
humans who have not been previously
infected,” he said. He expressed an
even darker possibility: The “remote
chance” that if it does manage to
enter the pig population, it could
mutate into something different, yet
another “novel coronavirus” that would
require a whole new scramble for a
vaccine.</p>
<p>“Honestly, I don’t know if we’re much
better off post-2009 than we were
pre-2009,” the WHO’s Webby said.
Governments devoted resources to
preventing the next big flu outbreak
for a few years, but interest faded as
the event receded into the past, he
said. With COVID-19, “we’re really
seeing for the first time in most
people’s living memory the impacts
these pandemics can have on society.
So I’m hoping a silver lining from
this will be more sustained resources
into preparedness.”<strong> <br>
</strong></p>
<p>Another possibility would be to
rethink how we produce meat. The
coronavirus pandemic has sparked calls
to ban “wet markets”—the informal food
markets that often include live wild
animals, the possible point at which
SARS-CoV-2 jumped from bats to people.
As Wallace points out, globally, the
biomass of the animals we eat—their
sheer physical weight—is now “far
greater” than their wild counterparts.
“Planet Earth is basically Planet
Farm,” he said. “When you populate the
globe with cities of hogs and poultry,
you’re going to generate novel
pathogens” that confound human
immunology, he added. Maybe the fear
of another pandemic will finally force
us to ramp down the scale of our
livestock operations and adapt to
diets that depend on way less meat.</p>
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