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Flu Outbreak -- Nature Biting Back at Industrial Animal Production?
April 25, 2009 | 06:39 PM (EST)
http://www.huffingtonpost.com/david-kirby/swine-flu-outbreak----nat_b_191408
.htmlSwine 

Officials from the CDC and USDA will likely arrive in Mexico soon to help
investigate the deadly new influenza virus that managed to jump from pigs
to people in a previously unseen mutated form that can readily spread among
humans.

One of the first things they will want to look at are the hundreds of
industrial-scale hog facilities that have sprung up around Mexico in recent
years, and the thousands of people employed inside the crowded,
pathogen-filled confinement buildings and processing plants.

Industry calls these massive compounds "confined animal feeding
operations," or CAFOs (KAY-fohs), though most people know them simply as
"factory farms." You have seen them before while flying: Long white
buildings lined up in tightly packed rows of three, four or more. Within
each confinement, thousands of pigs are restricted to indoor pens and
grain-fed for market, while breeding sows are kept in small metal crates
where they spend most of their lives pregnant or nursing piglets.

In the last several years, U.S. hog conglomerates have opened giant swine
CAFOs south of the border, including dozens around Mexico City in the
neighboring states of Mexico and Puebla. Smithfield Foods also reportedly
operates a huge swine facility in the State of Veracruz, where the current
outbreak may have originated. Many of these CAFOs raise tens of thousands
of pigs at a time. Cheaper labor costs and a desire to enter the Latin
American market are drawing more industrialized agriculture to Mexico all
the time, wiping out smaller, traditional farms, which now account for only
a small portion of swine production in Mexico.

"Classic" swine flu virus (not the novel, mutated form in the news) is
considered endemic in southern Mexico, while the region around the capital
is classified as an "eradication area" - meaning the disease is present,
and efforts are underway to control it. For some reason, vaccination of
pigs against swine flu is prohibited in this area, and growers rely instead
on depopulation and restriction of animal movement when outbreaks occur.

U.S. and Mexican epidemiologists and veterinarians will surely want to take
swine samples from Mexican CAFOs and examine them for the newly discovered
influenza strain (No one knows exactly how long it has been in
circulation). And though it is too early to know if this new virus mutated
and incubated on Mexican hog CAFOs, the industrialized facilities
unquestionably belong on the list of suspects.

Pigs are nature's notorious "mixing bowls" for inter-species infections,
and many swine flu viruses have long contained human influenza genetic
components. Then, in the late 1990's - when industrialized swine production
really took off in North America - scientists were alarmed to find that
avian influenza genetic material was also mixed into the continent's viral
soup (see below). Fortunately, it was not the dreaded and lethal H5N1
strain, which most people know of as "bird flu."

So where did this new, virulent and highly infectious influenza emerge
from? According to Mexico's Health Minister, Jose Angel Cordova, the virus
"mutated from pigs, and then at some point was transmitted to humans." It
sure sounds like something happened on some farm, somewhere.

For years, leading scientists around the world have worried that
large-scale, indoor swine "factories" would become breeding grounds for new
pathogens that could more easily infect humans and then spread out rapidly
in the general population - threatening to become a global pandemic.

We know that hog workers in Europe and North America are far more likely
than others to be infected with potentially lethal pathogens such as MRSA
(Methicillin-resistant Staphylococcus aureus), drug-resistant E. coli and
Salmonella, and of course, swine influenza. Many scientists also believe
that people who work inside CAFOs are more at risk of contracting and
spreading these and other "zoonotic" diseases than those working in
smaller-scale operations, with outdoor pens or pasture and far lower animal
density.

But until now, hog workers with swine flu have rarely gone on to infect
other people, save for close family members. And that is why this new
strain of swine influenza virus is so vexing - and alarming. It seems to
spread quite easily through casual human contact.

This new strain making headlines and killing people contains genetic
components of human flu virus, avian flu virus and - for the first time
ever - two types of swine flu virus: American and Eurasian. "Such a
combination of components (genes) was not found so far, neither among
humans nor among pigs (as far as we know)," CDC spokesman Tom Skinner said
in an email.

Nobody yet knows whether the mysterious mixing of two continents' swine flu
genes is what made this outbreak so deadly, and so infectious among people,
but you can bet that the world's best labs are already on the case. Another
possibility is that a new and more aggressive strain of avian influenza got
into the new mix as well.

How could this happen? There are several plausible explanations.

A New Avian Component?

Avian influenza viral components can easily mix with swine flu virus to
create new bugs - and this can happen on both traditional hog farms and
inside CAFOs, scientists say.

Last year, the Pew Commission on Industrial Farm Animal Production issued a
lengthy report on factory farming that included research on emerging forms
of avian-swine-human influenza viruses. The molecular forensics of rapidly
mutating animal pathogens makes epidemiological investigations all the more
challenging, it said. "Populations exposed to infectious agents arising in
CAFOs are even more difficult to define as some agents - such as a novel
avian influenza virus - may be highly transmissible in or well beyond a
community setting," the Pew report stated.

The transmission of avian or swine influenza viruses to humans, the report
said, (almost wistfully, in retrospect), "seems a rather infrequent event
today."

But the commission also issued this grave and perhaps all-too prescient
warning:

    The continual cycling of swine influenza viruses and other animal
pathogens in large herds or flocks provides increased opportunity for the
generation of novel viruses through mutation or recombinant events that
could result in more efficient human-to-human transmission of these
viruses. In addition, agricultural workers serve as a bridging population
between their communities and the animals in large confinement facilities.
This bridging increases the risk of novel virus generation in that human
viruses may enter the herds or flocks and adapt to the animals.


    Reassortant influenza viruses with human components have ravaged the
modern swine industry. Such novel viruses not only put the workers and
animals at risk of infections, but also potentially increase zoonotic
disease transmission risk to the communities where the workers live. For
instance, 64% of 63 persons exposed to humans infected with H7N7 avian
influenza virus had serological evidence of H7N7 infection following the
2003 Netherlands avian influenza outbreak in poultry. Similarly, the
spouses of swine workers who had no direct contact with pigs had increased
odds of antibodies against swine influenza virus. Recent modeling work has
shown that among communities where a large number of CAFO workers live,
there is great potential for these workers to accelerate pandemic influenza
virus transmission.

"We met with a team of researchers from the University of Iowa who are
studying avian flu, and their real concern was the very scenario that may
have happened in Mexico - that avian flu may get into a swine CAFO and
rapidly mutate and then get passed to workers, and then on to other people
very quickly," Bob Martin, who was executive director of the now-disbanded
commission and currently a Senior Officer at the Pew Environmental Group,
told me.

"Their concern was that new strains of avian flu combining with swine flu
could make the swine flu more deadly," he said. "And because viruses pass
so easily between pigs and people, the new avian component could make swine
flu more virulent."

Researchers such as Gregory Gray, MD, a University of Iowa professor of
international epidemiology and expert in zoonotic infections, warned that
CAFO workers could serve as a "bridging population" to rural communities
sharing viruses with the pigs, and vice-versa. Other scientists suggested
that CAFO workers could theoretically spread disease quickly to great
distances. An outbreak of infectious avian flu on the Eastern Shore of
Maryland, for example, could reach the Rocky Mountains within 36 hours.

The Iowa team was also worried that CAFO production could lead to another
1918-style global pandemic. One theory behind that calamity is that
waterfowl cross-infected U.S. pigs with a new type of avian-swine
super-virus that was quickly transmitted to farm workers, possibly in Iowa,
who went off to military training camps for WWI, and then spread the
pathogen worldwide

"One very big concern was that swine flu mixed with wild bird flu, or bird
flu in a chicken CAFO, tended to be ripe for incubating new types of viral
infections, especially since the animals are so densely packed together,"
Bob Martin said.

Hog CAFOs are supposed to be completely closed environments, in order to
protect the pigs from outside diseases. Visitors are usually required to
shower and don special protective clothing (again, for the animals'
benefit) before going inside a confinement.

But these are not hermetically sealed environments, and pathogens can enter
and exit a CAFO in a number of ways other than via swine workers (or flies,
another proven vector of CAFO diseases).

To begin with, some swine CAFO's recover water from their waste lagoons and
recycle it back into the animal housing, in order to wash out the barns
while also cutting down on dwindling groundwater supplies (a particular
concern in parts of Mexico, to be sure). But wildfowl routinely land in
CAFO lagoons, where they can easily shed influenza virus into the water.
This can also happen at facilities that use water from nearby ponds or
rivers.

Here in the U.S., the National Pork Board had already urged all producers
to take a number of steps to reduce the risk of avian-to-swine influenza
transmission (A new advisory has also been posted today).

"It is in the best interest of both human public health and animal health
that transmission of influenza viruses from pigs to people, from people to
pigs, from birds to pigs and from pigs to birds be minimized," says the
group's website, Pork.org.

"The global reservoir of influenza viruses in waterfowl, the examples of
infection of pigs with waterfowl-origin influenza viruses, the risks for
reassortment of avian viruses with swine and/or human influenza viruses in
pigs, and the risk for transmission of influenza viruses from pigs to
domestic turkeys all indicate that contact between pigs and both wild and
domestic fowl should be minimized," the Pork Board says. It then offers
some "potentially useful" factors to "reduce transmission of influenza
viruses between birds and pigs":

    ? Bird-proofing - All doorways, windows and air-flow vents in swine
housing units should be adequately sealed or screened to prevent entrance
of birds.


    ? Water treatment - Do not use untreated surface water as either
drinking water or water for cleaning in swine facilities. Likewise, it may
be prudent to attempt to minimize waterfowl use of farm lagoons.

    ? Separation of pig and bird production - Do not raise pigs and
domestic fowl on the same premises.

    ? Feed security - Keep pig feed in closed containers to prevent
contamination with feces from over-flying waterfowl.

    ? Worker biosecurity - Provide boots for workers that are worn only
within the pig housing units, thus eliminating.

Dr. Liz Wagstrom, the board's director of veterinary science, said she did
not know if Mexican producers followed the same precautions, though she did
note that none of the Mexican herds under US contract have reported any
unusual health problems.

As for the use of surface water sources on U.S. pig farms, Wagstrom said it
does happen, but her group is moving to avoid that practice industry-wide.
She added that the new virus has not been detected in any U.S. pigs, and
there is no importation of live swine from Mexico.

When Pig Viruses Collide

The CDC, USDA and Mexican authorities will surely focus on this previously
unheard of viral "reassortment" that combines swine influenza components
from both American and Eurasian strains.

Pigs don't fly, so how could this happen? One explanation, again, is the
birds. Every year, more than two million wild fowl fly up to 1,500 miles or
more eastward across the Arctic Ocean from Asia to North America. There,
the migrating Asian birds intersect with North American species along the
great north-south "flyways" of the Americas. There is sharing of viruses
between bird species from both continents, UI's Dr. Gray told me.

Last October, a team from the U.S. Geological Survey published a study in
Molecular Ecology that found genetic evidence of (non-H5N1) flu viruses in
northern pintail ducks in Alaska whose genes were more closely related to
Asian bird flu strains than those in the Americas. "Although some previous
research has led to speculation that intercontinental transfer of avian
influenza viruses from Asia to North America via wild birds is rare, this
study challenges that," Chris Franson, a USGS wildlife biologist, told
reporters.

The question, then, is could the Asian avian virus contain swine flu
components from Eurasian pigs?

"Absolutely," said Ellen Silbergeld, professor of environmental health
sciences at Johns Hopkins Bloomberg School of Public Health, and a leading
researcher of pathogen evolution in CAFOs. "A pig infected by avian virus
can then come into contact with swine virus, which then combines and gets
picked up by a bird again. It's a viral patchwork. Wild birds can carry
virus with swine components in it - a lot of avian viruses contain elements
from pigs."

Silbergeld is by no means convinced that birds brought the Eurasian genetic
material to Mexico.

"Pig's don't fly, but pork does," she said. "There is an active
international transfer of all kinds of animal products, including food,
food components, animal waste, offal, feed made of rendered animals and so
on. Some of it is imported from Asia or Europe."

And of course, people fly, too. Dr. Silbergeld thinks that human travel is
the most likely way that Eurasian swine viral components made their way to
Mexico. "A tourist from China could have gone to Mexico City, and that
Asian strain was picked up by somebody else, who then went to a swine
barn," she suggested. "It's a likely explanation. Sometimes we overestimate
what wild birds can do."

But no matter how the Eurasian strain got to Mexico, Dr. Silbergeld thinks
the genetic swimming pool that is found in modern swine - or poultry -
production is probably the place from whence this killer bug evolved.

"CAFOs are not biosecure," she told me. "They have high rates of
ventilation and enormous number of animals that would die of heat stress
unless the building was ventilated. We and others have measured bacteria
and viruses in the environment around poultry and swine houses. They are
carried by flies, too. These places are not bio-secure going in - or going
out."

"These mixing bowls of intensive operations of chickens and pigs are
contributing to speeding up viral evolution," Dr. Silbergeld added. "I
think CAFOs are contributing."

But, what about traditional outdoor farms? Aren't those animals even more
susceptible to wild type viruses than animals kept indoors, as industry
claims? "Well, let's say that animals in confinement are ten times less
likely to be infected by wild animals," she said, "But there are 100 times
as many of them. You do the math."

The Pork Board's Dr. Wagstrom said her industry has been working closely
with the US Government for nearly a year to set up a new monitoring and
rapid animal-identification system for emerging swine flu strains in the
U.S. herd. Wagstrom added that the new virus "could have" emerged from a
Mexican swine CAFO, though she doesn't think birds were involved.

"Where it happened is not as important right now as locating the virus, and
stopping its spread," she said. "There will be lots of epidemiology done in
the future to find out where this came from."

One hopes the hard detective work will get underway as soon as humanly
possible.