Coronavirus: Intensive farming provides perfect conditions for viruses to spread between animals and humans, study shows

Stop the Wildlife Trade: 'I think this is a wake-up call to be more responsible about farming methods, so we can reduce the risk of outbreaks of problematic pathogens in the future,' say scientists

Kate Ng
Wednesday 06 May 2020 16:38 BST
The WHO and governments globally are facing pleas to halt the sale of animals in unhygienic conditions and wildlife trade

Current intensive farming techniques involving overuse of antibiotics, high numbers of animals, and low genetic diversity are hotbeds for pathogens to spread, scientists have said.

A team of researchers led by the University of Sheffield and Bath studied the way a bacteria commonly carried by chickens and cattle behaved and spread between different species.

The bacteria, known as Campylobacter jejuni, are resistant to antibiotics due to the use of drugs in farming, and can be transferred to humans if they eat undercooked meat and poultry, causing gastroenteritis or food poisoning.

Gastroenteritis is the inflammation of the stomach and small intestine, and can lead to diarrhoea and vomiting, according the NHS.

A cattle-specific strain of the bacteria emerged in the 20th century when livestock farming grew exponentially across the world. According to agricultural data by the House of Commons Library, the number of cattle on UK farms increased from six million to 15.2 million between 1875 to 1974.

The authors of the study, published in Proceedings of the National Academy of Sciences, suggest that intensive farming practices led to changes in cattle diet, anatomy and physiology. This in turn triggered gene transfers between general and cattle-specific strains of the bacteria, helping it “cross the species barrier and infect humans”.

Researchers hope the study will hep scientists predict potential future problems posed by farming methods to prevent another epidemic from occurring.

Professor Dave Kelly, who led the study at the University of Sheffield, said; “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.

“Human activities have had a profound effect on the Earth’s ecosystems and biodiversity, particularly among livestock species, such as cattle. Escalating livestock numbers and global trade have been linked with the emergence of zoonotic diseases that pose a significant threat to both animal and human health, with the current Covid-19 pandemic being the most dramatic and serious example to date.”

Currently, there are an estimated 1.5 billion cattle on Earth, said Professor Sam Sheppard of the University of Bath. If around 20 per cent of these cattle are carriers of the bacteria, “that amounts to a huge potential public health risk”, he said.

“Over the past few decades, there have been several viruses and pathogenic bacteria that have switches species from wild animals to humans: HIV started in monkeys, H5N1 came from birds, now Covid-19 is suspected to have come from bats.

“I think this is a wake-up call to be more responsible about farming methods, so we can reduce the risk of outbreaks of problematic pathogens in the future,” added Prof Sheppard.

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