COVID-19 should be a wake up call to humanity. Most of the viruses affecting humans originated in animals and jumped to humans as a result of our use and interaction with animals for food.
By Bronwyn Slater
Virtually all of the viruses and communicable diseases that are endemic in the human population originated in animals. ‘Zoonotic disease’ is the term used to describe viruses and bacterial infections which originated in animals and then ‘jumped’ to humans. These diseases began to emerge when humans started to domesticate animals around 12,000 years ago.
When humans and animals are in close contact viruses can jump species and mutate in ways which allow them to survive and spread in the human population. The flu virus which circulates every year can be traced back to the 14th century or earlier. This virus originally jumped from pigs to humans. The measles virus originated in cattle and was the number one killer of young children for many centuries before a vaccine was found. Even today, 745,000 children die each year from this disease. AIDS originated in chimpanzees and is believed to have jumped to humans who had butchered them for meat. The Spanish Flu of 1918 killed 50 million people. It is thought to have originated in wild birds, then jumped to humans and mutated.
New zoonotic viruses have appeared with increasing frequency over the past 70 years. The reasons for this include increased globalisation, intensive factory farming, slaughterhouses, wet markets, the illegal wildlife trade, increased urbanisation, destroyed habitats and climate change. All of these provide the perfect conditions for new viruses to arise, as we describe below.
60% of the communicable diseases affecting humans are zoonotic, and in the last decade alone 75% of them have come from animals. There are around 200 known zoonotic diseases but there are more in existence and the majority are yet to be discovered.
Table of Zoonotic Diseases – in reverse chronological order
The table below lists some of the well known zoonotic diseases, beginning with COVID-19, throughout the last century and beyond. It is highly likely that they are all linked with animal agriculture.
The following diseases were not included – either because their origin is unknown or because they did not originate from animal agriculture:
- Tuberculosis – origins largely unknown.
- Smallpox – origin is unknown. It has been with humanity for about 3000 years.
- Chickenpox – The ancestral Varicella-Zoster Virus (VZV) that causes chickenpox and shingles co-evolved with apes and humans.
- Bubonic plague – wiped out half of Europe’s population in the Middle Ages and was transmitted by rats and fleas.
- Common Cold – has been with humanity throughout history. May have had its origin in camels or birds.
Evidence points to COVID-19 originating from animals, most likely horseshoe bats, and transferred via pangolins in wet markets where live and dead creatures (both wild and domesticated) are sold as food and slaughtered on demand.
0.07 to 16%
Fever, cough, difficulty breathing
370,000 to June, 2020
Bird Flu - H7N9
Wild birds are the natural hosts of bird flu viruses which can spread to chickens in intensive poultry farms where the virus can easily mutate and spread. Humans contract the virus through handling, eating or slaughtering infected poultry. Most H7N9 infections in people result from contact with infected poultry, by visiting wet markets or having contact with places where infected poultry have been kept or slaughtered. The virus is now ubiquitous in Chinese poultry.
Headache, cough, diarrhoea, stomach pains, aches, bleeding nose and gums
Caused by a coronavirus that jumped from bats to camels. Camels raised in high density systems for milk, meat, wool and for racing in the Middle East are thought to have been the source of human infection.
Respiratory infection ranging from asymptomatic to severe pneumonia
Swine flu is a new strain of H1N1 resulting from a reassortment of bird, swine, and human flu viruses, further combined with a pig flu virus. It is believed to have originated in an intensive pig farm. Millions of pigs infected with swine flu have been killed. Studies have shown that 30% to 50% of pigs in the US have been infected with swine flu.
Flu like symptoms, fever, chills, runny nose, cough, fatigue, nausea
Cave-dwelling bats passed the virus on to humans when they were captured and brought to markets.
The virus normally circulates among specific types of fruit bats. Bats can transmit the virus through infected air droplets, saliva, and excrement. Animals can become infected by eating food contaminated by bats and can transmit the virus to humans. The emergence of Nipah virus in Malaysia in 1998 was linked to intensification of pig production at the edge of tropical forests where the fruit bats live.
Fever, cough, headache, shortness of breath, confusion
Virus originated in non-human primates such as chimpanzees, and is thought to have made the jump to humans as the result of the hunting and eating of chimpanzees by humans.
Weight loss, fever, pneumonia, sore throat, mouth ulcers, flu like symptoms, memory loss
Bats, monkeys and chimpanzees were the original source. Humans can become infected from handling and/or eating any of these infected animals.
Fever, haemorrhage, vomiting, diarrhoea
Hong Kong Flu - H3N2
It descended from H2N2 through a genetic process in which genes from multiple subtypes reasserted to form a new virus. The new subtype arose in pigs infected with avian and human viruses and were soon transferred to humans. Pigs were considered the original intermediate host for influenza because they supported reassortment of subtypes. However, other hosts such as poultry appear capable of similar coinfection, and direct transmission of avian viruses to humans is possible.
Chills, fever, muscle pain, weakness
African fruit bat is the reservoir host. Humans and primates can be directly infected. The first humans infected had been using African green monkeys for experimentation.
Severe haemorrhagic fever
Asian Flu - H2N2
It originated from a mutation in wild ducks combining with a pre-existing human strain. These viruses can jump to humans either directly from birds or poultry, or through an intermediate host, such as a pig.
Fever, body aches, chills, cough, weakness, loss of appetite.
Bird Flu - H5N1
Wild water-birds, such as ducks, geese, swans, gulls, terns and shorebirds are the natural hosts of bird flu viruses. The virus can spread to chickens in intensive poultry farms, where the virus can easily mutate and spread in the flock. Humans contract the virus through handling, eating or slaughtering infected poultry.
Caused by the H1N1 influenza virus of avian origin. One theory is that the virus infected humans directly from birds before the pandemic and that it adapted or mutated in humans into the one causing the outbreak. In other words, it evolved via the mixing of bird and human viruses in human hosts. Another study suggests that the parent virus went from humans to birds then back to humans in a more lethal form. Domestic poultry can easily be infected with the virus from wild birds.
Typical flu symptoms
14th century or earlier
The influenza virus crossed the species barrier from ducks to waterfowl to pigs and from there to humans. Birds serve as a reservoir for a vast diversity of flu viruses to which all the major human pandemics trace their origin. The domestication of pigs was also a factor in the spread of the virus.
Fever, cough, sore throat, runny nose, fatigue, aches and pains
650,000 per year
Measles virus emerged from rinderpest (cattle plague) as a zoonotic disease between AD 1100 and 1200. Measles (MeV) is thought to have evolved in an environment where cattle and humans lived in close proximity.
Skin rash, runny nose, cough, fever, sore throat
200 million between 1855 and 2005
Factory Farms are Ticking Time Bombs
90% of farmed animals across the world are now kept in factory farms where the animals live in crowded, dirty, densely populated sheds. Intensive farming allows viruses and bacteria to spread easily throughout a flock. The animals’ immune systems are compromised as a result of the stress of being crowded together in these unnatural conditions.
Michael Greger, author of ‘Bird Flu: A Virus of our own Hatching’ says: “When we overcrowd animals by the thousands, in cramped football-field-size sheds, to lie beak to beak or snout to snout, and there’s stress crippling their immune systems, and there’s ammonia from the decomposing waste burning their lungs, and there’s a lack of fresh air and sunlight — put all these factors together and you have a perfect-storm environment for the emergence and spread of disease.”
70% of the antibiotics produced worldwide are given to animals in intensive farms in order to prevent the spread of bacterial infections. However, antibiotics are powerless against viruses. Humans who work in factory farms risk becoming infected or becoming hosts for viruses which can subsequently mutate and spread in the human population.
Researchers at the University of Sheffield and Bath have warned that intensive farming, involving overuse of antibiotics, high numbers of animals, and low genetic diversity are hotbeds for pathogens to spread. The researchers say: “Human pathogens carried in animals are an increasing threat and our findings highlight how their adaptability can allow them to switch hosts and exploit intensive farming practices.”
New research shows the next global public health crisis could come to us through industrial animal agriculture. The study, published in Proceedings of the National Academy of Sciences in May 2020, shows that contemporary farming methods—including the overuse of antibiotics, high numbers of animals crammed into small spaces, and a lack of genetic diversity—make it more likely that pathogens will spread to people from farm animals and create an epidemic for humans.
The Scientific Task Force on Avian Influenza and Wild Birds says: “Typically, highly pathogenic avian influenza outbreaks are associated with intensive domestic poultry production and associated trade and marketing systems.”
In the US, Senator Cory Booker has proposed legislation to impose a moratorium on the country’s biggest factory farms and phase them out completely by 2040.
Leah Garces, president of Mercy for Animals says: “We’ve been ringing the alarm bells for a long time. My deep hope is that now people will make the connection — factory farming is a catastrophic risk to our species — and that this permanently changes our behaviour in the long term”.
Slaughterhouses are petri dishes for zoonotic pathogens. Author Mike Davis refers to slaughterhouses as “vast excremental hells, containing tens of thousands of animals with weakened immune systems suffocating in heat and manure while exchanging pathogens at blinding velocity with their fellow inmates.”
Bush Meat and Wet Markets
Wet markets sell live and dead animals and sometimes slaughter the live animals in front of customers. The live animals at these markets are highly stressed. Their immune systems are compromised and they can easily become infected with pathogens. When wild and domesticated animals are put together in large numbers in awful conditions, in close proximity to each other and to people, there is a high risk of these viruses mutating into a form that can infect people. This is how COVID-19 is believed to have originated.
Bushmeat is the name for any wild animal that is killed for consumption including antelopes, chimpanzees, rats, porcupines, snakes and fruit bats. The use of bats as food is a particular concern as bats are reservoirs for more zoonotic viruses than most other animals. In Africa’s Congo Basin alone, people eat an estimated five million tonnes of bushmeat per year. In Ghana it is thought that more than 100,000 bats are killed and sold every year.
Hunting, butchering, handling, cooking and eating wild animals can lead to the transmission of zoonotic diseases through animal bites, scratches, body fluids, tissues or faeces.
Deforestation is a major contributor to recent virus outbreaks, and cases of Ebola have often occurred close to recently deforested land. A number of researchers today think that it is humanity’s destruction of biodiversity that creates the conditions for new viruses and diseases like COVID-19 to arise. It is possible that it was human activity such as road building, mining, hunting and logging that triggered epidemics like Ebola.
Invading and disrupting ecosystems can shake viruses loose from their natural hosts. David Quammen, author of ‘Spillover: Animal Infections and the Next Pandemic’ says: “We invade tropical forests and other wild landscapes, which harbour so many species of animals and plants—and within those creatures, so many unknown viruses.”
Potential for deadly pandemics
The H5N1 bird flu virus has a high mortality rate (60%) but a relatively low number of deaths have been recorded. However, scientists are extremely concerned that if this virus mutates to become more easily transmissable between humans, we could be facing a deadly pandemic with a range of deaths between five and 150 million.
H7N9 is another bird flu virus with pandemic potential. H7N9 doesn’t spread easily between people. However, virologist Professor Yoshihiro Kawaoka of the University of Wisconsin said: “If H7N9 viruses acquire the ability to transmit efficiently from person to person, a worldwide outbreak is almost certain”.
Superbugs or antibiotic-resistant bacterial infections result from the overuse of antibiotics. 70% of the world’s antibiotics are used in animal agriculture. Because of this we now have a serious global threat of antimicrobial-resistance (AMR).
In 2016, a UK government review warned that the 700,000 global deaths caused by AMR each year will rise to 10 million by 2050 if no action is taken. This means that antimicrobial-resistance could kill more people than cancer.
What do we need to do:
- Go Vegan – Thereby ending animal agriculture and animal use
- End deforestation and restore ecosystems
- End the trade in wildlife
Going vegan is the most powerful thing we can do in order to address the threat of pandemics and many other problems. It entirely removes the demand for animals and animal-derived products. Deforestation will end as there will no longer be a need to create pasture for grazing cattle, and there will no longer be any trade in wildlife – for food or medicinal purposes. Ecosystems can be restored as the land-mass required to grow plants for food is a fraction of that required for animal farming.
- “The evidence suggests wide-scale adoption of a plant-based diet may result in a decreased threat of zoonotic disease.” – Joyce et al (2012).
- “Shifting to plant-based farming has the unparalleled ability to restore habitats by freeing up an area of land equivalent to the US, China, European Union and Australia combined.” (Science, 2018).
370,000 people have now died worldwide since the COVID-19 outbreak began. If we use this opportunity to make the changes necessary to avoid such outbreaks in future then their deaths will not have been in vain.
“One Root Cause of Pandemics Few People Think About” – Scientific American
“Industrial animal farming has caused most new infectious diseases and risks more pandemics, experts warn” – article from the Independent
“Destroyed Habitat creates the perfect conditions for Coronavirus to emerge” – Scientific American
Is Factory Farming to blame for Coronavirus – The Guardian
Zoonoses – a ticking time bomb – Viva!
Big Farms Make Big Flu – by Rob Wallace
Scholarly articles and scientific papers:
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