““Factory farms are the best way to select for the most dangerous pathogens possible,” said Rob Wallace, an evolutionary biologist at the Agroecology and Rural Economics Research Corps in St. Paul, Minnesota. To explain why, he offered a crash course in zoonotic transmission, from the point of view of the pathogen.
“If you’re a pathogen in a host,” Wallace said, “you don’t want to kill your host too fast before you can get into the next host — otherwise you’re cutting off your own line of transmission. So there’s a cap on how much of a badass you can be. The faster you replicate, the more likely you end up killing your host before the next host can come along.”
If you’re deep in the wildernessor on a small farm, you (the pathogen) are not going to regularly come across hosts, so you’ve got to keep your virulence, or harm inflicted on the host, pretty low so that you don’t run out of hosts. “But if you get into a barn with 15,000 turkeys or 250,000 layer chickens, you can just burn right through,” Wallace said. “There’s no cap on your being a badass.”
This is part of why factory farms are a bigger risk for zoonotic outbreaks than the natural world or small farms.
The biologist added that because we’re increasingly trading poultry and livestock across international borders, we’re ramping up the danger even more. Strains that were previously isolated from each other on opposite sides of the world can now recombine.
“Take influenza,” Wallace said. “It has a segmented genome, so it trades its genomic parts like card players on a Saturday night. Usually, most hands are not too terrible, but some hands come out much more dangerous. An increase in the rate of recombination means an explosion in terms of the diversity of pathogens that are evolving.”
The world has already seen a really frightening example of this. Between 1997 and 2006, highly pathogenic strains of H5N1 bird flu were linked to poultry farms in China.
“Our entire understanding of how bad a pandemic could potentially be changed in 1997 with the emergence of the H5N1 avian influenza virus. All of a sudden, there was a flu virus that was killing over half the people it infected,” Greger said.
When people became infected with H5N1, it had a 60 percent mortality rate. For comparison, experts estimate that Covid-19’s mortality rate is probably somewhere in the neighborhood of 1 percent to 3 percent, though these estimates continue to evolve and vary widely by country and by age. (If you’re wondering why H5N1 didn’t become as big a deal as Covid-19, it’s because it mostly infected poultry rather than people; it wasn’t as good at infecting humans as the coronavirus unfortunately is.)”
“The other pandemic risk associated with factory farms has to do with “highly drug-resistant forms of bacterial pathogens,” as Shah put it — that is, antibiotic resistance.
When a new antibiotic is introduced, it can have great, even life-saving results — for a while. But as we start to use and overuse antibiotics in the treatment of humans, crops, and animals, the bacteria evolve, with those that have a mutation to survive the antibiotic becoming more dominant. Gradually, the antibiotic becomes less effective, and we’re left with a disease that we can no longer treat.”
““We have abundant evidence documenting the fact that when you put animals in crowded, unsanitary conditions and use low-dose antibiotics for disease prevention, you set up a perfect incubator for spontaneous mutations in the DNA of the bacteria,” said Robert Lawrence, a professor emeritus of environmental health at John Hopkins University.
“With more spontaneous mutations,” he explained, “the odds increase that one of those mutations will provide resistance to the antibiotic that’s present in the environment.” Those resistant bacteria could become strains that spread all over the world. “That’s the biggest human health risk of factory farms.””
” factory farming presents us with a double bacterial risk. Say a bacterial outbreak emerges among chickens. The poultry can pass that bacteria on to us humans, causing serious infection. We’d normally then want to use antibiotics to treat that infection, but precisely because we’ve already overused antibiotics on our farmed animals, the bacteria may be resistant to the antibiotic. If the infection happens to be one that transmits well between people, we can end up with an untreatable bacterial pandemic.”
“Laborers in meat plants are typically stationed very close together along processing lines, which makes social distancing all but impossible.”
“We can absolutely have a meat production system that is better for human health, the climate, and animal welfare — if we’re willing to abandon factory farming.
“The de-intensification of the livestock industry would go a long way toward reducing pandemic risk,” Greger said. “I mean decreasing long-distance live animal transport, moving toward a carcass-only trade, and having smaller and less-crowded farms. Basically, the animals could use a little social distancing, too.””
“We also need to reintroduce more biodiversity into our farms. Raising animals that are slightly different from each other genetically (rather than selecting for specific genes) will build in immunological firebreaks to help prevent the spread of infectious diseases”