As COVID-19 has spread rapidly through the world, scientists continue to work to identify the source of the disease. While the origin is still not known, a strong possibility is that 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, not unlike on 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.
People may worry less about the transmission of a virus from animals to humans if they don’t eat wildlife. However, the conditions on factory farms — where most of U.S. animal food products originate — are similar to those of wildlife markets, and could be the source of the next pandemic. In fact, the H1N1 influenza outbreak of 2009 originated in an industrial pig farm in North Carolina, the Nipah virus was also transmitted from pigs to humans, 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 major 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 then subsequently be passed back to animals, a process called spillback. Spillback is particularly dangerous, as it gives the pathogen even more time to evolve into a more dangerous and/or more transmissible disease.
A 2020 paper by Humane Society International identifies five primary pandemic risks associated with intensive agriculture:
- Virus ‘spillover’: when expansion of farms into previously wild areas brings wild and domestic species together.
- Viral amplification: where novel viral strains are created through 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 huge 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 then evolve over time 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 tight within a containment area that offers little to no space between animals. Additionally, they are stressed, and therefore have 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 shows that the coronavirus has 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 human — the only known animal-to-human transmission outside the original source. To protect public health, European governments took the drastic step of killing nearly 20 million mink at infected farms, which nonetheless still remain reservoirs for the virus.
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 practically 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 make its way into water systems. Also, although the consistent presence of antibiotics is provided in an attempt to maintain healthy animals, the reality is that it can create more serious illnesses. Strains of pathogenic, antibiotic-resistant bacteria, for example, are transferable to humans though 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.
Learn more:
- Wildlife Markets and the Coronavirus, MSPCA
- The Fur Trade, MSPCA
- Animals That Infect Humans Are Scary. It’s Worse When We Infect Them Back. The New York Times (January 19, 2022)
- An HSI report: The connection between animal agriculture, viral zoonoses, and global pandemics, Humane Society International (September 2020)
- COVID-19 and Animals, Centers for Disease Control
- Understanding CAFOs, Centers for Disease Control
- Coronavirus: Fear over rise in animal-to-human diseases, BBC (July 6, 2020)
- Factory farms and pandemics, U.S. PIRG website
- Coronavirus could drive the last nail into the mink fur trade, CNN (October 18, 2020)
- Federal legislation, MSPCA
- Farmers and animal rights activists are coming together to fight big factory farms VOX (July 8, 2020) This article includes information about S. 3221/H.R. 6718, the Farm System Reform Act.
- Question 3 Prevails with 78% of the Vote, MSPCA
