I want to share a resource prepared by Cynthia Schuck and Wladimir Alonso, two public health experts who are also passionate about the plight of farm animals. They’ve prepared a short free e-book to provide factual information on the connection between farm animals and pandemics to the general public.
Below are excertps from the E-book. All info in this post should be credited to the authors (Cynthia and Wladimir).
A brief account of our history with animals
In our interactions with wild animals, companions, livestock and commensals, pathogens commonly known to us were imported: scavenging and hunting gave us tapeworms, and probably hepatitis and poliomyelitis through the hunting of our close relatives, primates; companion animals, rabies; livestock gave us measles, Salmonella, smallpox and anthrax (a disease that became famous for its potential use as a biological weapon); commensals, the plague, hantavirus and typhus. Of course, the reverse is also true: most human infectious diseases can also be transmitted to animals.
But the advancements in technology and the rapidly growing population were also catalysts of a massive increase of food animal populations and the intensification of farming practices, which accelerated sharply in the decades following World War II. As is discussed in the E-book, these conditions created efficient routes for the transmission of pathogens that gained, or re-gained, access to human populations. We are now in what scientists call the ‘third epidemiological transition’, characterized by a resurgence of familiar infections along with the emergence of new ones. Many have their origin in those animals we use as food.
With the human population approaching 8 billion people interconnected in a global village, where all forms of interactions with animals (from hunting to industrial complexes with enormous numbers of animals) are not only still present, but amplified (80 billion land animals are used for meat every year), new challenges are bound to happen in the form of local epidemics and global pandemics 6–9. These challenges will test not only our ability to react to these events appropriately, but also to identify (and rectify) the elements that most contribute to their emergence.
Direct contact with wild viruses
The brutality of Ebola (its death rate and the dreadful course of the illness on patients) is well known. Ebola is one among many other infectious diseases that find its way into humans when we expose ourselves to the large diversity of viruses that are tolerated by wild animals, but that can be harmful if they spill over to people. In the case of the Ebola outbreak in West Africa, such a jump was traced back to a two-year-old boy from Meliandou, a small village in Guinea. The boy used to play with other children in a hollow tree full of bats. According to the villagers, children would sometimes catch them, and perhaps even roast them on sticks to eat them.
Eating wild animals is an important route of human exposure to pathogens harbored by wild animal species. Of course, it is not the only one: another popular means of human infection is through a vector, such as a mosquito or a tick, through which the pathogen makes its way from an animal to a person. Yet, because every infection transaction requires the intermediation of a middleman (the vector), the spread of the disease can be addressed more objectively by targeting the vector. In contrast, diseases that find their way to a person, and from that single human case (the ‘patient zero’) can be transmitted from human-to-human in a sustained way are more likely to become pandemic, especially if transmission occurs through behaviours that are common (such as physical greetings, sharing of objects, close proximity and sex).
There are many ways through which pathogens can find their way to human beings without the help of a vector. In the water, breathing dust from highly contaminated environments (such as caves), eating food chewed by infected animals or having close physical contact with those animals are among them. But one route that has been particularly important is the use of wild animal species as food. The origin of most Ebola outbreaks – which still happen, mainly in Central Africa – is believed to be associated with the consumption of bushmeat. It is not so much the consumption of a cooked animal that is risky, but the process of hunting and butchering the animal. In this (literally) bloody affair, plenty of opportunities exist for the direct exposure of vulnerable human tissues (skin wounds, mucosa) to the pathogens and for the cross-contamination of other food items with the bodily fluids of the infected animal. Humans were most likely infected with precursors of the human immunodeficiency virus (HIV) in this way, when hunting chimpanzees for meat. Interestingly, chimps got infected in the same way, when hunting two other smaller species of primates. HIV infection, which leads to the acquired immunodeficiency syndrome (AIDS), has spread to all corners of the globe since the 1980s, with 39 million people killed of HIV/AIDS-related complications as of 2018.
Based on those accounts, one could hope that the prevention of infectious diseases imported from wildlife would be just a matter of addressing these practices and the standards of life of populations on the fringes of urban societies. Unfortunately, the outbreaks of SARS in 2002-03 and the 2019 pandemic remind us that this is not the case.
SARS and COVID-19 outbreaks can be also traced back to the consumption of wild animals, but not in small villages from poor rural areas of developing countries. Both SARS and SARS-CoV-2 emerged in the wet markets of vibrant urban centers in China. In the case of SARS-CoV-2, the origin has been pinpointed to Wuhan, the most populous city in Central China, with approximately 11 million people .
Wet markets are places where animals are sold for consumption, along with other perishable goods. Described this way, they would not be different from countless other grocery stores or street markets around the globe. What makes some of those places different is not only the large diversity of animal species that are sold, but also the way in which many are kept on display, to be butchered on site on the customers’ request. Cages and stand spaces are so limited that animals are mostly crammed into tight spaces, piles and shelves, where lower levels are constantly flooded with the droppings of upper ones. Wild animals (such as turtles, bamboo rats, badgers, hedgehogs, otters, civet cats, snakes, bats, pangolins) might have been taken directly from the wild, but more often they are raised in the numerous farms run by family enterprises. Many pathologists and virologists have warned authorities of the public health dangers that these conditions represent 6,7,25. The regular mixing of a high diversity of pathogens, from wild and domestic species, in an environment of acute stress for the animals and poor sanitary conditions, and where hosts from all species meet, creates the perfect conditions for the emergence of novel pathogens that can make their way to humans, be it through a wound, the cross-contamination of food or by the air, through the aerosolization of organic material.
Inconvenient truth
We tend to approach each new epidemic and public health crisis independently, rather than recognizing their common drivers. Domesticated animals have served humanity for millenia, but in today’s modern societies we must be honest and admit that the way we commonly raise animals is a major threat for global health and the well-being of human populations. Moreover, the extensive human and financial losses associated with infectious disease outbreaks and drug resistance make this an enormous economic and social problem too. As global meat consumption continues to rise even further (it has doubled in the last 50 years, from a global average of 20 kilograms per person in 1961 to around 43 kilograms in 2014122), these risks and costs are expected to increase even further.
The world spends billions every year in the design and control of measures to protect us against infectious diseases. In 2015, funding for the investigation of emerging and zoonotic diseases in a single US institution, the Centers for Disease Control, was nearly half a billion dollars 121. The annual cost of pandemic preparedness alone is estimated to lie somewhere within $ 3 billion to $ 5 billion 123. Yet it is disturbing that many of the most basic control policies supposed to be well established have failed when tested, even in high income countries such as the United States 121. Should we insist on making public health safety an exclusively reactive endeavor?
While large investments are currently being poured into the development of vaccines and treatments to control the damage of the 2019 coronavirus outbreak, these (most needed and welcomed) developments are unlikely to shield us from a future epidemic. We must have this same sense of urgency to accelerate the development of modern methods of food production, which include the development of substitutes of animal protein. In fact, this is a revolution in the food sector that has already started, with a diverse range of products on that menu that include meat-like products made from plants or even grown in vats 124. Ultimately, however, the demand for alternative protein sources must come from the population, and the market will respond appropriately. Just as we exercise our citizenship by adopting the necessary measures to curb the advancement of COVID-19 and protect our communities, we must also exercise it with our wallets at the supermarket, and think how best our purchasing and dietary choices can build a safer future for generations to come.
