Industrial animal agriculture is a significant cause of deforestation and disease, leaving scientists concerned that pandemics will become more frequent.
As a researcher who studies communicable diseases, Simon Reid has plenty to ponder right now.
Speaking over the phone from Queensland, with the sound of birds squawking in the background, Dr Reid says the first half of 2020 has been surreal. A virus leapt out of the contagion models he has studied for years and into everyday life in the form of a global pandemic.
He is also frustrated that the work of his colleagues has mostly been ignored – for years, communicable disease experts have been warning of exactly this scenario.
“There’s definitely a sense that ‘you were warned’ and we had a couple of dry runs of this,” Dr Reid, an associate professor at the University of Queensland, says.
“We had SARS-coronavirus in 2003, that was like a warning shot from the wildlife.
“There’s not too many surprises in what’s happening. This is basic ‘infectious diseases 101.”
Next pandemic is ‘a probability, not a possibility.’
At the time of writing, COVID-19 has affected nearly 5 million people globally, killing more than 300,000.
Governments are having to chart a path between more deaths and one of the worst recessions in history. Meanwhile, World Health Organisation officials say the virus may be with us forever. Although it seems like a freak biological phenomenon – a so-called “black swan” event – the emergence and spread of coronavirus is anything but. In fact, warnings of a pandemic eerily similar to SARS-CoV-2 appear in published research and reports spanning multiple decades.
The leader of the US government’s Ebola response warned in 2016 a serious pandemic from an airborne infectious disease “was a question of when not if.”
In 2017, the research team who discovered the origins of SARS – which shares 80 per cent of its genetic sequence with SARS-CoV-2 – warned that all the ingredients were in place for the virus to strike again, as its close relative did just two years later.
And as recently as September last year – just a few months before COVID-19 was detected in China – an independent watchdog set up by the WHO warned the world was “grossly” unprepared for the “very real threat” of a pandemic.
But even more alarming is what the new coronavirus indicates about the future.
Researchers say human impacts on the natural world are causing new infectious diseases to emerge more frequently than ever before, meaning the next pandemic – one perhaps even worse than COVID-19 – is only a matter of time.
“We know that it’s a probability, not a possibility,” Dr Reid says.
“The roulette wheel will start to spin again.”
“If you don’t resolve the conditions that generated the problem, then we sit waiting for the next probability equation to come through.
“And it will, and sadly it’s possible that it’s in our lifetime.”
The growing threat to human health
Nearly all emerging pathogens like COVID-19 come from “zoonotic transfer” – essentially when a virus present in animals jumps to infect humans.
The US Centers for Disease Control and Prevention estimates three out of every four new infectious diseases, and nearly all pandemics, emerge this way.
Researchers have counted around 200 infectious diseases that have broken out more than 12,000 times over the past three decades. On average, one new infectious disease jumps to humans every four months.
Animal species like civet cats (SARS), camels (MERS), horses (Hendra), pigs (Nipah) and chimpanzees (HIV) have all been implicated in the spread of new viruses at different times.
SARS-CoV-2, the virus at the centre of the current pandemic, is thought by some researchers to have been carried by the critically endangered pangolin. This elusive, nocturnal animal has been virtually eaten to extinction.
A man holds a pangolin at a wild animal rescue centre in Cuc Phuong, outside Hanoi, Vietnam September 12, 2016. (Reuters: Kham)
Although these animals are a natural reservoir, the research is clear: human societies and practices are almost always responsible for the spillover of new diseases.
“Disease emergence is all about increased opportunity for contact… it’s all about human impact on the natural system that increases the contact between humans and animals,” says Hume Field, a veterinarian who helped trace the animal origins of the Hendra virus in Australia and the SARS virus in China.
These contacts at the human-animal interface are varied and complex. Cutting into forests or previously undisturbed ecosystems, often to expand agricultural land, drives out pathogens that were locked in the wild. Biodiversity and habitat loss helps diseases spread among wild animals.
Dense human populations living together in greater numbers in cities facilitate their spread.
Industrial agriculture means animals are often kept in crowded and stressful conditions that lower their immune defences.
“Land use change, demographic change and agriculture,” Dr Reid explains.
“They are three of the 10 drivers for disease emergence, and everything else in the top 10 is associated with those three things.”
A group of scientists writing in the Lancet in 2015 concluded that far-reaching changes to the Earth’s natural systems posed a growing threat to human health, naming emerging diseases alongside climate change as one of these threats.
For these researchers, governments and health authorities need to address what drives mass epidemics rather than just respond to individual diseases if we want to avoid the next outbreak.
SARS ‘a warning shot from the wildlife.’
Tracing the animal origins of a virus – a crucial part of preventing future outbreaks – can seem like a detective search, one that takes years, or even decades, to unravel.
It involves testing surfaces in wildlife markets, contact tracing back to the earliest known cases and tracking and catching tiny animals in the wild. With an estimated 1.67 million unknown viruses in the wild, Dr Field says it is no easy task.
“It really can be like finding a needle in a haystack,” says Dr Field, a science and policy advisor for China and Southeast Asiawith EcoHealth Alliance.
It took 15 years for the genetic “smoking gun” for SARS to be only published in 2017, 15 years after the initial case. Scientists tracked the virus to a single population of bats living in a remote cave in Southern Yunnan, about 1,000km from where it was first detected in humans in 2002.
The search for both SARS and COVID-19 has focused on the exotic food trade and China’s wet markets, where wild and domesticated animals are sometimes kept in close contact with humans. It’s an environment that increases the likelihood of viral spillover events.
Calls for the markets to be shutdown echo the response that followed the SARS epidemic, when the Chinese government undertook a “patriotic” extermination campaign of 10,000 masked palm civets, a type of cat prized for their meat, which was initially believed to be the original reservoir of the virus.
Only later did it come out they were an intermediate animal host and were likely amplifying a previously unrecognized coronavirus of bats.
Wet markets are under fire again today, despite a quarter of the initial cluster of cases having no contact with the Huanan Seafood Market in Wuhan, and some data on COVID-19 molecular evolution suggesting the first passage to humans occurred nine months earlier than thought.
Responses to the markets in the West have often hinted at disgust at Chinese eating habits. But although wet markets can be vectors for disease spread, disease emergence happens all over the world, and in many different contexts.
“[People think] … emerging diseases happen in places where they have wildlife or where there’s not good hygiene or something like that. That’s part of the story. But the reality is that a lot of these things are socio-economic,” Dr Field says.
Swine flu, the first pandemic of the 21st century, was spread around the world by export from large piggeries. Hendra virus emerged from land-use changes on the peri-urban outskirts of Brisbane.
Like COVID-19, SARS spread rapidly on passenger jets, leading the WHO’s regional director, Dr Shigeru Omi, to designate it “the first emerging disease of the age of globalization.”
Even bats, which have gained a bad reputation for their role in COVID-19, are susceptible to these human-induced environmental changes.
Bats, deforestation and Ebola
The catastrophic Ebola outbreak in West Africa in 2014 is an illustrative example of why most outbreaks of bat-borne zoonotic diseases are linked to human activity.
The virus has been called “the most deadly communicable disease known to man.”
In two-and-a-half-years after Ebola was first detected in Guinea, the epidemic killed 11,310 people – about 40 per cent of those infected.
The virus is believed to have spilt over from bats because of local hunting practices and the reliance of millions of people on wild animal “bushmeat” for survival.
From there, the virus spread through an increasingly dense and mobile population, with Guinea’s underfunded health system and deep poverty offering little resistance.
However, Ebola outbreaks occurred in Africa and were brought under control on more than two dozen occasions over 40 years. And genetic evidence suggests the strain of Ebola responsible for the 2014 outbreak may have been circulating in the region for at least five years prior.
What changed before 2014 for the virus appear far from its usual haunts in Central Africa, let alone in Guinea — a country where Ebola had never been seen before?
The World Health Organisation has noted that Guinea’s Forested region where Ebola emerged has been as much as 80 percent deforested by clear-cut logging, and by foreign mining and agriculture companies.
Bats, Dr Reid says, are particularly vulnerable to overhunting and habitat destruction.
“Deforestation is actually driving bats into areas in greater numbers where perhaps they might not have been before and where humans are present,” he says.
Evolutionary biologist Rob Wallace and others have noted that the global thirst for palm oil has lead to deep-cutting into forests, a disturbance that could be increasing human and fruit bat contact in the dry season, when Ebola virus disease outbreaks often happen.
As the second most diverse group of mammals after rodents, bats host more than 65 known human pathogens, including many coronaviruses, most of which ordinarily circulate harmlessly.
They are also a keystone species that control insects and pollinate and disperse seeds of the plants that humans and animals depend on.
Deforestation partly explains why, although bats have had close contact with humans for thousands of years, pandemics have emerged only recently.
It’s an ongoing problem in the developing world – between 1990 and 2010, Latin America lost 88 million hectares to deforestation, according to the UN’s Food and Agriculture Organisation.
The leading cause was the conversion of forests to farmland and pasture, as it is in Australia, the only developed nation to make the World Wildlife Fund’s (WWF) global list of deforestation hotspots.
And it creates ideal conditions for vectors to breed and spread infectious diseases.
“Agriculture, to me at least, is about land-use change, and the effect that then has on the loss of wildlife community and wildlife structure,” Dr Field says.
Where to from here?
In February, a group of researchers – including seven from the CSIRO – wrote that emerging diseases had been left out of the growing interest in how global environmental change impacts human health.
Most attention, they wrote, has been on climate change, pollution and extreme weather.
“By contrast, little attention has been paid to the interactions between environmental change and infectious disease emergence, despite growing evidence that causally links these two phenomena,” the authors wrote.
Without addressing these causal links, governments could be forever playing catch-up: treating the symptoms of disease emergence at ever greater human and economic cost, rather than addressing the conditions that lead to the next one.
SARS cost an estimated US$30 to 50 billion despite causing illness in fewer than 9,000 people at the start of the millennium.
A final tally for SAR-CoV-2 is yet to be determined, but the pandemic has already halted the global economy, thrown millions onto unemployment, killed hundreds of thousands and cost national governments trillions of dollars globally.
Dr Reid says addressing disease emergence is an example of a “wicked problem” — a complex issue dependent on so many variables that it can be impossible to determine what exactly the problem is, let alone how to tackle it.
Zoonotic diseases are particularly complex because they overlap multiple sectors – environment, agriculture, and health – that are often siloed from one another.
Dr Reid says his dream project would bring together researchers with knowledge of across multiple fields, including from human and animal medicine, ecology, sociology, microbiology and those who study the transmission of pathogens in humans, wildlife, and livestock.
It’s an idea sometimes described as a “One Health” perspective.
“The chances of getting that [project] funded in Australia are nil,” Dr Reid says.
From this perspective, the emergence of this pandemic reveals how connected human societies are to animals and the natural world. Like climate change, it is another reminder that, in a fundamental way, the health of human societies is directly linked with the health of the planet.
For Dr Field, COVID-19 also shows the urgency of gaining a better understanding of how and why new diseases might be emerging.
“You know, when these things happen, [we assume] they happen somewhere else for some reasons that don’t concern us,” he said.
“I think the perception is that people think they happened there, but they won’t happen to us.
“And I think that is dangerous complacency.”
Original source: https://www.abc.net.au