Scientists continue to work to identify the source of COVID-19, and while the origin is still unknown, one possibility is that it jumped from animals to people in a wildlife market. In wildlife markets, sometimes called “wet markets,” a variety of species are kept in highly cramped quarters, similar to factory farms. At some wildlife markets, customers can purchase an animal to be slaughtered on the spot. Such wildlife markets exist around the world, including in the United States.
The conditions on factory farms — where most U.S. animal food products originate — are similar to those of wildlife markets, which could potentially be the source of the next pandemic. For example, the 2009 H1N1 influenza outbreak originated in an industrial pig farm in North Carolina and the H5N1 avian influenza was transmitted from poultry to humans.
Zoonotic diseases — diseases that can spread from animals to humans and vice versa — are a significant public health concern, with an estimated 75% of emerging infectious diseases among humans being zoonotic. Further, once a pathogen has spilled over from nonhuman animals to humans, it can be passed back to animals, a process called spillback. Spillback is particularly dangerous, giving the pathogen more time to evolve into a more hazardous and transmissible disease.
A Humane Society International paper identifies five primary pandemic risks associated with intensive agriculture:
- Virus ‘spillover’: when the expansion of farms into previously wild areas brings wild and domestic species together.
- Viral amplification: where novel viral strains are created by confining vast numbers of stressed animals indoors.
- Farm concentration: where dense geographic concentration of farms increases the risk of pathogens spreading.
- Global live animal trade: where vast numbers of live animals are transported between countries and continents, allowing pathogens to spread even further.
- Live animal markets, agricultural fairs, and auctions: where “hubs” are created such that animals from many different places are brought into proximity with the public.
In terms of viral amplification, during swine flu or avian flu outbreaks, factory farms, in particular, can act as evolution vessels. Many diseases that start in wildlife, such as birds or bats, are not viable in humans at first, but when introduced to hog and poultry farms, viruses evolve to be able to infect humans.
To ensure “quality control,” animals on hog and poultry farms are virtually genetically identical, making for less variation wherein less susceptibility to a virus could emerge. Animals are also packed tightly within a containment area that offers little to no space between animals. Additionally, they are stressed, therefore suffering from weakened immune systems. Pigs, and often poultry, are also genetically similar to both wildlife and humans, so they act as the ideal evolution center for viruses to transform from a wildlife disease to a zoonotic one.
Problems, however, are not limited to factory farms where animals are killed for food. Evidence has shown that the coronavirus spread on European and U.S. mink fur farms, where hundreds of millions of wild, fur-bearing animals are confined in small, barren, wire cages. In Denmark and the Netherlands, farmed mink spread the mutated virus to humans, the only known animal-to-human transmission outside the source. To protect public health, in 2020, Denmark took the drastic step of killing 17 million mink at infected farms, where Covid-19 had been documented as spreading from human to mink, mutating, and then spreading back to humans. Learn more about the link between fur farms and pandemics.
A final concerning factor for transmission and a pandemic outbreak is that factory farms regularly overuse antibiotics. Many factory farms prophylactically administer low doses of antibiotics in animal feed, and the CDC notes that 70% of all antibiotic use in the U.S. is on factory farms. About half of the antibiotics used are nearly identical to those used in humans.
Regular low-dose antibiotic use can lead to extreme health risks for both humans and animals. As portions of the antibiotics aren’t fully metabolized, they will show up in manure, which can enter water systems. Also, although the consistent presence of antibiotics is provided to maintain healthy animals, the reality is that it can create more severe illnesses. Strains of pathogenic, antibiotic-resistant bacteria, for example, are transferable to humans through the handling of meat or manure.
To decrease the health risks that come with factory farming, we encourage consumers to demand better welfare and regulations for the farms. The USDA and the World Health Organization have taken steps to oppose antibiotic use and set stricter governance for how antibiotics can be used. However, until animals are given proper spacing, food, enrichment, and even genetic variation, the problem of emerging zoonotic diseases will persist.
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