Industrial farming of livestock a ticking pathogen bomb, scientists say

An illustration.
PHOTO: Perry Tse

Industrial farming of livestock may offend the sensibilities of many people, with animals crushed into pens where they are barely able to stand up, among other distressing images.

But some scientists warn such methods are also breeding grounds for mass production of new diseases.

Three years before the virus that causes Covid-19 started making people sick in China, another novel coronavirus began circulating in the southeast of the country. It was fatal, but its victims were 25,000 piglets, not humans.

That outbreak was swiftly followed in 2018 by a scourge on a much larger scale – the Ebola-like African swine fever , which does not infect humans but killed at least 100 million pigs as it raged across China.

It threw the country’s pork industry into crisis and sent the price of China’s favourite meat soaring. The disease is still spreading in Asia.

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This flurry of outbreaks and the possible link between the Covid-19 human pandemic to China’s wildlife trade has pressed the authorities to tighten rules.

In addition to a ban in February on trade of wildlife for human consumption, China said it would revise or enact several laws related to the control of diseases in or linked to animals over the next two years.

Some regulations, like those updating the animal epidemic prevention law, would be introduced “as soon as possible”, said Zhang Yesui on May 21. Zhang is the spokesman for the National People’s Congress, the country’s legislative body.

China aims to plug the holes that experts say have escalated past problems – low standards of biosecurity, lack of oversight and responsibility, as well as local government cover-ups of outbreaks.

Biosecurity covers methods to prevent disease outbreaks in animals as well as to protect crops from infections and pests.

But veterinary epidemiologist Dirk Pfeiffer says with animals this is not just a China issue; it is a bigger global problem around the competing demand to raise livestock to feed growing populations and of managing the disease risks for animals and humans that come with the expansion of meat production.

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“This is the real story – the connection between our food systems, our meat production and infectious disease,” said Pfeiffer, a professor at City University of Hong Kong.

Meat from the wildlife trade was only one piece of a much bigger picture, Pfeiffer said, pointing to the vast scale of livestock production that came with economic growth.

“It’s a numbers game – the more dense the biomass, the more opportunity for spread of infectious disease,” he said.

Livestock – which makes up 60 per cent of the biomass, or total weight, of mammals globally – compares with just 4 per cent for wild animals, according to researchers at the Weizmann Institute of Science in Israel in 2018.

‘It looks efficient’

The way livestock is raised in industrial-scale farming not only skews biodiversity, it also creates a pathogen bomb for potential disease outbreaks, experts say.

“Cheap chicken, cheap cow, it’s the creation of a pathogen factory … [it] looks like an efficient system, but the costs of failure – and the risk – is high,” said Richard Kock, a professor of wildlife health and emerging diseases at the University of London’s Royal Veterinary College. “It sits there as a time bomb.”

Pathogens can get into livestock farms in a number of ways, including via feed or water contaminated with viruses from bat or bird droppings or humans coughing and sneezing.

But in large-scale, high-density farms, the viruses can spread quickly through the ranks of cows, pigs, or poultry, with ample opportunity to mutate, recombine and otherwise “practise their ability to invade cells”, including those of humans, Kock said.

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This threat may be recognised but it is not being sufficiently monitored, said Gregory Gray, an infectious disease epidemiologist and professor at Duke University.

“We are artificially increasing our human risk from some pathogens, because they are allowed to thrive in these domestic animals, and we don’t have a good pulse on it,” he said.

An example: the H1N1 influenza in 2009, the first flu pandemic in 40 years, was first identified in the United States and only later linked to pig farms in Mexico.

The risk of disease broadens as the domestication of animals expands, such as the breeding farms for “wild” animals in China, which may have had a role in the current Covid-19 pandemic, Kock said.

The World Health Organisation has said that since the 1970s about 70 per cent of emerging pathogens came from animals, which it calls a “burgeoning threat” because “animals are intensively farmed, transported for trade and kept in close contact with other species and humans in market places”.

The Food and Agriculture Organisation of the United Nations (FAO) puts it this way: “Economic growth is accompanied by an increase in consumption of animal products … Changes in livestock production increase the potential for new pathogens to emerge, grow and spread from animals to humans on a global scale.”

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Global meat production grew nearly 20 per cent between 2005 and 2015, according to an FAO report. By 2028 production was likely to be up an additional 13 per cent, the agency predicted last year.

This intensification of livestock production around the world has many forms, from large industrial farms to the growth of smaller, so-called backyard farms that may be on the periphery of forests, butting up with wild animal habitats and creating spillover risks, experts say.

And viruses exploit whatever points of entry are made available.

That is why Juergen Richt says industrialised farming can be part of the solution. The university distinguished professor at Kansas State University’s College of Veterinary Medicine argues that such farms are the ones with the resources needed to build the biosecurity controls to keep people and animals safe from disease.

Some of these farms are taking stringent measures, Richt said. He notes a recent trip to a pig farm in Ecuador where outside vehicles were zoned off, and he needed to quarantine three days before entering and then change clothes twice and shower upon arriving and leaving.

“The small backyard farmer cannot introduce these kinds of measures,” he said.

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China’s transition

This has been one lesson for China in the wake of its African swine fever outbreak, which wiped out 40 per cent of its pig herd in the space of a little more than a year.

China has seen outbreaks this year and while officials say the disease is on a “downward trend”, they have called for vigilance to prevent a rebound.

Now the country is “on a fast track” to replacing the small-scale farms that have dominated the industry with large, industrialised farms that can afford tighter biosecurity controls, according to Holly Wang, an agricultural economist at Purdue University in Indiana.

This year’s proposed revisions to the animal epidemic prevention law may speed up China’s transition to more modern, large-scale production due to the costs of compliance, Wang said.

The draft revisions, which include inspection and quarantine measures for legally bred wild animals, provide more defined guidelines for identifying and eliminating animal diseases. They also clarify the responsibilities of local government, industry groups and farm operators in countering disease.

The latest reforms follow decades of growth in China’s meat consumption, starting from the opening of the economy in the late 1970s and reflecting the country’s development.

In the past two decades, meat demand has grown nearly 20 per cent, according to Angela Zhang, head of business intelligence at IQC Insights, a Shanghai-based agricultural consulting firm.

But other countries are just starting out on their own surges in such demands, making the global situation of disease control a patchwork of different systems and levels of capability.

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For example, a 2019 FAO report focused on Kenya said there would be “an exponential increase” in the demand for animal source foods as GDP per capita was projected to increase over 140 per cent by 2050. This would increase the risk of emergence and spread of zoonotic diseases, the report said.

“In 2050, with human and animal densities expected to double, the impact of such an outbreak on society could be even higher.”

Many countries “struggle to find a balance between sustainable development and meeting the rapid increase in the demand for food”, according to Latiffah Hassan, a professor in veterinary public health and epidemiology at the Universiti Putra Malaysia.

“There is no perfect way to respond to an emerging disease threat,” she said. “There will always be trade-offs.”

That is apparent in the varying opinions between experts in the field about how to solve the problem. Some stress increased surveillance and biosafety, while others call for sustainable practices and reducing global consumption.

Without a consensus, and as demand for meat continues to grow, Richt says the question remains: “Can we continue in the same way as we did it in the past, or do we have a train wreck in the making?”

This article was first published in South China Morning Post.