Industrial farming of animals such as pigs, poultry and cattle to provide meat for hundreds of millions of people can reduce the risk of pandemics and the emergence of dangerous diseases, including Sars, BSE, bird flu and Covid-19 versus less intensive farming, a major study by veterinarians and environmentalists has found.
Despite reports from the United Nations and other bodies in the wake of Covid linking intensive livestock farming to the spread of zoonotic (animal-borne) diseases, the authors argue that ‘non-intensive’ or ‘low-yielding’ farms pose a more serious risk to human health because they require much more land to produce the same amount of food.
This, it is argued, increases the chances of dangerous virus ‘spillover’ between animals and humans, as it leads to habitat loss, which displaces disease-carrying wild animals such as bats and rodents and brings them closer to farm animals and humans.
The report authorspublished 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 now greatly exceeds that of wild mammals and birds, and livestock hosts are increasingly more numerous than wild hosts for the pathogens they share,” the report says.
While eliminating animal farming would eliminate much of the risk of disease, say the authors, they argue that a dramatic reduction in meat consumption would be “hard” to achieve.
So the report instead looked at whether intensive or less intensive farming was a better option to reduce disease risk.
Intensive animal husbandry has been widely blamed for increasing the risk of avian and swine flu and other pandemics due to long-distance livestock movements, overcrowded farms, poor animal health and welfare, low disease resistance in animals and low genetic diversity.
But data on disease emergence on intensive farms is limited, the report says, and generally ignores how land use affects risk.
“High-yield or ‘intensive’ farming is blamed for pandemics, but those who call for a move away from intensive farming often fail to consider the counterfactual – the pandemic risk of agriculture less intensively and in particular the implications for land use,” says lead author Harriet Bartlett.
“Low-yielding farms need a lot more land to produce the same amount of food as high-yielding farms. A widespread shift to low-yield agriculture would result in the destruction and disruption of large areas of natural habitats. This increases the risk of viral spread [ie the first transmission from a wild animal] by disrupting wildlife that may well harbor the next pandemic virus and by increasing contact between wildlife, humans and livestock.
“Low-yielding farms typically involve larger livestock populations, lower biosecurity, more workers, and larger crop area, which result in different, but not necessarily lower, disease risks than high-yield systems. yield producing the same amount of food,” says the report by veterinarians and ecologists from the universities of Cambridge and Leeds.
A global shift away from intensive agriculture would require an area of land almost as large as India, inevitably increasing the risk of fallout, Bartlett says. “The conversion and fragmentation of natural habitats means that we farm in places where livestock and people [come into closer contact] with stressed wildlife populations.
The evidence that zoonotic diseases appear more often in intensive farming systems than in extensive ones is hotly debated, with governments and the £150 billion a year poultry and livestock industries arguing that intensive farming is generally extremely safe and now essential. Animal welfare activists argue that these farms are hotbeds of disease.
The report says poultry farms described as both “industrial” and “backyard” played a role in the 2004 highly pathogenic avian influenza (HPAI) outbreak in Thailand. However, which played a bigger role – “spillover in ‘backyard’ production due to poor biosecurity allowing contact between wild and domestic birds, or amplification and reassortment of low pathogenicity? to high in “industrial” systems” – remains open to debate.
It is generally believed that the intensive farming of pigs near bat colonies led to the emergence of the Nipah virus in pigs and humans in 1999, and Mers in Saudi camels. World Health Organization investigators have said Covid is likely to have originated from a Chinese wild animal farm before being widespread in a “wet” urban market.
Dr Guillaume Fournié, an epidemiologist at the Royal Veterinary College in London, said supposedly better biosecurity in intensive farming was not always a defense against the spread of disease.
The recent wave of bird flu epidemics in Europe had “shown how difficult it can be to ensure optimal biosecurity standards and how this can lead to further spread in areas with high livestock densities,” he said.
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