Human Culpability in COVID-19 and Other Zoonotic Diseases

Being responsible and sheltering at home is one way to limit the spread of COVID-19. Changing our relationship with wildlife and farm animals, however, would help keep deadly zoonotic diseases out of the human population to begin with.

Photo by kapulya
Photo by kapulya

While much speculation exists about the origin of COVID-19, the near-total consensus among epidemiology experts is that it originated in a wild animal and infected humans at a live animal market in Wuhan, China. At such open-air markets, domestic and wild animals—live and dead—are sold for human consumption. 

COVID-19 is a zoonotic disease, one that “jumps” or “spills over” from animals to humans. The original source was likely a bat—like other coronaviruses, COVID-19 exists naturally in bat populations, where it does not necessarily harm the host animal. However, before it jumped to humans, an intermediate host may have been involved —perhaps a pangolin, since they, as well as bats, were sold at the market and are known to play host to similar viruses. (The sale of bats at the market was legal, while the sale of pangolins was not. Widespread, illegal trade in pangolin meat and scales—used in traditional medicine—is rampant and is devastating pangolin populations.)

COVID-19 is but the latest in a long and accelerating history of such diseases. The Centers for Disease Control and Prevention (CDC) estimates that at least 70 percent of new and emerging infectious diseases are zoonotic. With our interconnected world, these zoonotic disease outbreaks spread rapidly and, with relative ease, become global pandemics. While COVID-19 almost certainly emerged from direct contact with wildlife, other zoonotic diseases are transferred to humans via domestic animals. 

In just the past 40 years, the worst pandemics and epidemics—including SARS, Ebola, HIV/AIDS, the H5N1 avian flu, the H1N1 swine flu, and COVID-19—have all happened against a backdrop of increasing trade and consumption of wildlife and destruction of wild habitat and an increasing number of farm animals warehoused in concentrated animal feeding operations (CAFOs). So, while the origins are sometimes shrouded in mystery and subject to scientific sleuthing, the answer as to which species is responsible for the COVID-19 pandemic—as well as other disease outbreaks—is clear: It’s us. 

Wildlife Trade
The ever-growing global wildlife trade is bringing people and animals into close and prolonged contact in ways that enable diseases for which we have no immunity to spill over to humans. Live wild animals are traded domestically and internationally as pets, food, and for use in laboratories and zoos, while dead wild animals and their parts are traded as food, traditional medicine ingredients, trinkets, trophies, and clothing. A sobering 18 percent of the planet’s known terrestrial vertebrate wildlife—over 5,500 species—are already part of the wildlife trade, with several thousand additional species predicted to enter the trade in the years to come. As more and more species become part of this trade, the likelihood of pathogen transmission will continue to rise. 

The United States is one of the top importers of such wildlife, having grown into the second largest market for wildlife trade in the world. A significant proportion of this multibillion-dollar industry is legal and largely unregulated. For example, tens of thousands of monkeys are imported for use in medical research and tens of thousands of birds and small animals, including African grey parrots, sugar gliders, and slow lorises, are imported for the pet trade. Permits may be required, but they are cheap and rarely denied. The regulations that do exist are often limited in scope and inadequately enforced. Animals in trade—even legal trade—are often transported under abysmal conditions. It is also very difficult to ensure that animals allowed in under the assertion that they were bred in captivity were not in fact caught in the wild.

The societal ramifications of wildlife trafficking are severe. According to the United Nations, “Wildlife trade is a big business, run by international criminal networks, trafficking wildlife and animal parts much like illegal drugs and arms.” The Al-Shabab terrorist group, to cite just one example, is partially funded by ivory poaching. UN Environment Programme Executive Director Achim Steiner warns, “The victims of wildlife crime are not only the animals and ecosystems that are devastated by poaching and trafficking, they are people as well. The human cost of poaching and illegal trade in wildlife is measured in lives lost to the criminal networks involved and livelihoods destroyed by the erosion of a natural economic foundation.” 

Moreover, legal and illegal wildlife trade are often inextricably linked, with legal trade used as a cover for trafficked animals and parts. And while stricter enforcement of domestic laws and international treaties could help, these laws and agreements are not focused on preventing zoonotic disease transmission and are therefore insufficient for preventing the next pandemic. Discussions are underway, therefore, on ways to revise national and international law to address zoonotic disease risks. Two areas of focus are live animal markets and the trade in wildlife itself. In April, a bipartisan group of US lawmakers called on the World Health Organization, the World Organisation for Animal Health, and the Food and Agriculture Organization of the United Nations to achieve “a global shut down of live wildlife markets and a ban on the international trade of live wildlife that is not intended for conservation purposes.” 

Meanwhile, habitat destruction around the world is accelerating, resulting in staggering declines in the abundance and diversity of wildlife, with over 1 million species facing extinction worldwide in the coming decades. When wild animals’ habitat is destroyed or degraded, the likelihood and frequency of humans coming into contact with those animals increases, as does the corresponding risk of pathogen transmission. Incidents of emerging zoonotic diseases have increased significantly since 1940, a trend that strongly correlates with accelerating habitat destruction. 

Animal Agriculture
We also catch zoonotic diseases from farm animals. This kind of transmission often occurs when a wildlife reservoir for a disease transmits an infective agent to a farm animal, which is then transmitted to humans. In addition to the human toll, this kind of transmission often leads to “depopulating” (killing, but not for consumption) of large numbers of farm animals suspected of carrying the virus, even when no diagnosis is confirmed. 

One example, avian influenza, is a viral infection originating in aquatic birds. While such viruses are particularly adapted to birds, they can be transmitted to humans who interact with infected birds. Once in humans, person-to-person transmission is possible. Highly pathogenic avian influenza strains can move through domestic bird populations rapidly due to the close, unhygienic conditions in which these animals are usually raised. Such strains are typically fatal to domestic poultry, and depopulation of infected flocks is extremely common globally to protect uninfected flocks. From December 2014 to June 2015, for example, nearly 50 million chickens and turkeys in the United States were killed after being exposed or potentially exposed to avian influenza. 

The 1918-1919 influenza pandemic that infected one-third of the world’s population and killed at least 50 million people was caused by an H1N1 virus with genes of avian origin. (The “H1” and “N1” refer to particular proteins that inhabit the outer shell of the virus.) In April 2009, a novel H1N1 swine flu strain, likely emerging from pigs in central Mexico, caused another global pandemic. Though it was less deadly than the 1918-1919 H1N1 virus, the CDC estimates that in the United States alone, 60.8 million individuals became infected in the year after the swine flu emerged, and over 12,000 of those people died. While it is unclear how many pigs may have been depopulated to prevent the spread of this virus, Indonesia ordered that 9 million pigs be inspected for the illness, and Egypt ordered the slaughter of all 300,000 pigs within the state where an outbreak occurred.

The Nipah virus, first identified in 1998 in Malaysia, can spread to humans from bats and pigs, food sources, and human-to-human contact. As of May 2018, about 700 human cases of Nipah virus had been reported, and 50 to 75 percent of these cases were fatal. A second outbreak in Kerala, India, occurred in May 2018, resulting in 17 human deaths. Millions of pigs were depopulated in Malaysia in response to the first outbreak to curb the spread of the disease. 

Current agricultural production practices greatly increase the risk of zoonotic disease transmission. In today’s industrial systems, the vast majority of farm animals are raised in CAFOs—factory farms where they are often confined by the thousands in crowded, unsanitary environments that facilitate the rapid transmission of virulent pathogens and infectious diseases from host to host. Farm animals in these environments may also experience high levels of stress from overcrowding and the inability to perform natural behaviors, which can weaken their immune systems and increase susceptibility to infection. 

The limited genetic diversity among farm animals—a result of decades of selective breeding to maximize productivity and efficiency—further contributes to the spread of disease in large-scale animal agriculture operations. A number of studies suggest that lack of genetic variation allows for pathogens to rapidly adapt to the host population and hinders the animals’ ability to develop resistance to the pathogen. 

And live animal markets are not only found “elsewhere.” At live animal markets across the United States, birds are held and slaughtered on-site, and pigs, cows, sheep, goats, domestic rabbits, and various species of wildlife, are confined in close proximity, further increasing the risk of disease transmission and outbreaks. To date, the United States has not taken steps to close down its live animal markets.
The routine administration of antimicrobials to farm animals—another byproduct of industrial farming—is also extremely troubling. In this case, though, it does not directly increase the risk of viral disease transmission, but rather hinders our ability to fight life-threatening bacterial infections. Although some antimicrobials are used in animal agriculture to treat disease and illnesses (some of which can be attributed to poor management practices and extreme confinement), the most controversial use of antibiotics in farm animals has been to promote growth and increase the efficiency with which animals convert feed to flesh. In recent years, the use of medically important antibiotics for growth promotion in animals has been outlawed in dozens of countries worldwide, and it has been prohibited in the United States since 2017. However, antibiotics may still be used in the United States for “disease prevention” in animals. (See AWI Quarterly, summer 2019). When provided in this manner for prolonged periods at low doses, such antibiotics help build bacteria’s resistance to them, and these antibiotic-resistant bacteria can be passed to humans, with devastating effects. According to the World Health Organization, antibiotic resistance is one of the biggest global threats to human health, food security, and economic development.

If we are to reduce the risk of future catastrophic zoonotic disease outbreaks, it is imperative that we recognize how our relationships with animals—particularly livestock and wild animals subject to trade—are exacerbating these risks and that we take immediate action to mitigate such risks. This includes curtailing wildlife trade and closing live animal markets in order to reduce the risk of disease transmission between animals and humans. While reining in wildlife trade will significantly aid in reducing the risk of future zoonotic disease in humans, we must also protect wildlife habitat to reduce direct contact with wild animals not tied to trade. And we must improve conditions for farm animals by transitioning to systems that promote human safety and the health and welfare of the animals, rather than prioritizing assembly line efficiency and productivity. 

Humanity has the capacity to prevent the next pandemic—we need only to exercise the will to do so, for the benefit of animals and people alike.

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