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  • When you think of an American farm,

  • you probably think of something like this.

  • A barn,

  • a field,

  • a diverse group of animals

  • Until relatively recently, if you ate meat,

  • it probably came from a farm that looked basically like this.

  • And that was true around the world.

  • But in the last few decades, the global production of meat has skyrocketed.

  • And that's been driven by a change in how livestock is raised.

  • In order to increase profits and raise livestock more cost-effectively,

  • farms like this one started to consolidate and to mechanize.

  • Take chicken farms for example.

  • In the 1970s, the US had around 30,000 chicken farms.

  • By 1995, it had only about 20,000.

  • But the amount of chicken produced in the US had tripled.

  • This is what one of those consolidated farms looks like.

  • Farms like this are controversial.

  • There are ethical concerns,

  • environmental concerns...

  • But infectious disease experts worry about them for a different reason.

  • A farm like this is called a concentrated animal feeding operation, or CAFO.

  • CAFOs are basically huge industrialized farming operations.

  • They contain tens of thousands of animals, sometimes hundreds of thousands of animals,

  • and they're often very crowded.

  • American CAFOs were efficient and profitable.

  • And soon, they became a model for farming all over the world.

  • Today, almost all the meat we eat comes from farms like this.

  • Factory farms supply an estimated 90 percent of meat globally

  • and around 99 percent of the meat we eat here in the US.

  • So if you're eating a burger or bacon or whatever it is today,

  • it probably came from a factory farm.

  • A CAFO is an environment built for one purpose: to house as many animals as possible.

  • What worries scientists is that that also makes it an ideal environment

  • for the pathogens that cause pandemics.

  • A virus is really just a bit of genetic code that makes copies of itself.

  • But that replication process isn't always perfect.

  • They're introducing lots of mutations as they replicate.

  • Martha Nelson studies viruses at the National Institutes of Health.

  • Most of those mutations are going to be deleterious and won't help the virus at all.

  • Lots of mutations just lead to the virus dying.

  • But occasionally, a mutation will happen that will give the virus a new ability:

  • to be more deadly, for example, or to be able to jump from one species to another.

  • A virus can only replicate when it's inside another organism — a host.

  • But it can only replicate inside a host for so long. Every host eventually dies.

  • That means, even if a virus does mutate in a beneficial way,

  • without hosts, that mutation will eventually die out.

  • And out in the wild, or even on a small farm, new hosts can be hard to come by.

  • But in a CAFO...

  • Let's say you're a pathogen. If you're in a factory farm,

  • where you have hundreds of thousands of potential hosts, it's a bonanza.

  • More hosts, means more chances to replicate, more chances to mutate,

  • and a higher likelihood that a mutated virus will survive.

  • In other words, factory farms are also factories for new viruses that we haven't seen before.

  • And that's also helped along by the larger system that CAFOs are part of.

  • There's a lot of international trade going on of live animals.

  • We're sending these animals from city to city and from country to country.

  • We're flying them across oceans.

  • Some viruses have a genetic code that's segmented into parts.

  • And sometimes, two of these viruses come into contact with each other.

  • Occasionally, you can have two separate viruses co-infect a single cell.

  • When they replicate, they can just kind of swap out entire segments with the other virus.

  • And through that, you can kind of create these chimeric, you know, offspring that have pieces

  • from the two parents.

  • Just like with mutations, this swapping and shuffling of segments between viruses is basically random.

  • And that means sometimes the new virus is a dud.

  • But every now and then, you hit jackpot, and you come up with a radically new combination

  • that has properties that neither of the two parents had.

  • In CAFOs, viruses have an opportunity to come into contact with each other all the time.

  • That's making it easier for a virus that exists over here on one side of the world

  • that normally would just stay on that side of the world,

  • to travel quite quickly to another part of the world.

  • With viruses from different parts of the world mixing and shuffling and mutating inside animals,

  • humans have made it very easy for a nasty virus to emerge.

  • And actually, it's happened already.

  • We are continuing to closely monitor the emergency cases of the H1N1 flu virus."

  • In 2009, a new virus quickly spread around the world.

  • It became known as the "swine flu" because of its links to pig farms in North America.

  • It came from the major swine production region that's right outside of Mexico City.

  • That particular virus was able to evolve there because you had pigs

  • coming from the United States over the border into Mexico. You have pigs from Europe.

  • And so you have this sort of mixing bowl of pigs from all over the world that are able to share their viruses

  • and exchange genetic components and create this really unusual pandemic variant.

  • By the time public health measures and a vaccine were able to get it under control,

  • swine flu had killed hundreds of thousands of people.

  • But viruses are just one kind of pathogen that CAFOs are really good at incubating.

  • Because bacterial disease can spread so easily in a CAFO,

  • farmers typically treat their livestock with antibiotics, which limits the bacteria's spread.

  • And often, every animal gets that antibioticwhether they're sick or not.

  • At first, that prevents bacterial disease from running rampant through the population.

  • But over time, just like viruses, bacteria will mutate.

  • The antibiotic will kill most of those mutations

  • unless the mutation gives them the ability to resist it.

  • And over time...

  • As the bacteria evolve, those that have the mutation to survive the antibiotic

  • will become more and more dominant.

  • This is how we end up with antibiotic-resistant bacteria.

  • And that becomes really dangerous if it spreads into humans.

  • And so then when we humans come along and try to treat the bacteria with antibiotics

  • in our own bodies, the bacteria might not respond to those antibiotics.

  • One way to lower the risk of CAFO-borne pathogens would be to change the CAFO system to make

  • the spread of pathogens harder.

  • We could decrease the long-distance transport of live animals.

  • We could have smaller and less crowded farms,

  • so that pathogens don't have so much opportunity to rip through huge numbers of animals.

  • But making CAFOs safer for humans wouldn't address other concerns about them,

  • like animals' quality of life, or the lagoons of liquid manure they produce.

  • Ending CAFOs entirely, and returning to a smaller model of farming, would.

  • It's actually entirely possible for us to have a meat production system that is better

  • for human health as well as for the climate and for the animals themselves.

  • We just need to abandon factory farming to get that.

  • We could also just eat less meat.

  • After all, the amount of meat we eat today is a recent development.

  • But now that we know what it's like to experience a pandemic,

  • we should understand the risks of the animal pathogens cooking in our food systems.

  • It's just a matter of time before one ends up in the human population.

  • Whether that happens next year, whether that happens in a decade,

  • that's a crystal ball. We don't know.

  • But we do know that we are playing with probabilities.

  • And we're continually increasing the probability

  • as we increase the pool of viruses in these farms.

When you think of an American farm,

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B2 Vox bacteria replicate meat factory antibiotic

The next pandemic could come from factory farms

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    林宜悉 posted on 2020/08/18
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