The industrial farming of animals such as pigs, poultry and cattle to provide meat to hundreds of millions of people could reduce the risk of pandemics and the emergence of dangerous diseases, including Sars, BSE, bird flu and Covid-19 compared to less intensive agriculture, according to a large-scale study by veterinarians and ecologists.
Despite reports from the UN and other agencies in the wake of Covid linking intensive livestock farming to the spread of zoonotic (animal) diseases, the authors argue that “non-intensive” or “low yield” farms pose a more serious risk to human health. health because they need much more land to produce the same amount of food.
This, it is argued, increases the potential for “spillover” of dangerous viruses between animals and humans, as it causes habitat loss, driving disease-carrying wildlife such as bats and rodents into closer contact with farm animals and humans.
The authors of the report, published in the journal Royal Society Open Science, recognize that rapidly increasing consumer demand for meat and other animal products poses a significant risk to humanity.
“The risks of emerging infectious diseases are increasing. Livestock biomass is now much greater than wild mammals and birds, and there are increasing numbers of wildlife hosts for pathogens they share,” it says.
While eliminating livestock production would eliminate much of the disease risk, the authors say, they argue that a dramatic reduction in meat consumption would be “challenging” to achieve.
Instead, the report looked at whether intensive or less intensive farming was a better option for reducing disease risk.
Intensive livestock farming is widely blamed for increasing the risk of avian and swine flu and other pandemics due to long-distance movement of livestock, overcrowded farms, poor animal health and welfare, low animal disease resistance and low genetic diversity.
But data on disease onset on intensive farms is limited, the report says, and generally ignores how land use affects risks.
“High-yield or ‘intensive’ livestock farming is blamed for pandemics, but those calling for a move away from intensive livestock farming often fail to consider the counterfactual – the pandemic risk of farming less intensive and in particular the impact on land use,” said lead author, Harriet Bartlett†
“Low-yielding farms need much more land to produce the same amount of food compared to high-yielding farms. A widespread conversion to low-yield farming would result in the destruction and disruption of vast natural habitats. This increases the risk of viral spillover [ie the first transmission from a wild animal] by disrupting wildlife that could harbor the next pandemic virus and by increasing contact between wildlife, people and livestock.
“Lower-yielding farms typically have larger livestock numbers, poorer biosecurity, more workers and more farmland, resulting in different, but not necessarily lower, disease risks than higher-yielding systems that produce the same amount of food,” says the report from veterinarians and ecologists at the universities of Cambridge and Leeds.
A global shift away from intensive farming would require an area nearly as large as India, inevitably increasing the risk of spillovers, Bartlett says. “The conversion and fragmentation of natural habitats means we are farming in places where livestock and people [come into closer contact] with stressed wildlife populations.”
Evidence that zoonotic diseases are more prevalent in intensive farming systems than in extensive farming systems is hotly debated, with governments and the £150bn a year poultry and livestock sectors claiming that intensive farming is generally extremely safe and now essential. Animal welfare activists argue that such farms are hotbeds of disease.
The report says that poultry farms described as both “industrial” and “backyard” played a role in the 2004 outbreak of highly pathogenic avian influenza (HPAI) in Thailand. Which played a larger role – “overflow into ‘backyard’ production due to poor biosecurity allowing contact between wild and domestic birds, or amplification and reshuffling from low to high pathogenicity in ‘industrial’ systems” – remains open to debate .
It is widely believed that intensive farming of pigs near bat colonies led to the emergence of Nipah virus in pigs and humans in 1999, and of Mers in Saudi Arabian camels. Researchers from the World Health Organization have stated that Covid likely originated in a Chinese wildlife farm before spreading in an urban “wet” market.
dr. Guillaume Fournié, an epidemiologist at the Royal Veterinary College in London, said better biosecurity on intensive farms was not always a defense against the spread of disease.
The recent spate of bird flu outbreaks in Europe has shown “how difficult it can be to ensure optimal biosecurity standards and how this could lead to further spread in areas with high density farms,” he said.
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