The overuse of antibiotics, crowded feed lots and other characteristics of intensive farming increase the odds that pathogens make the jump to humans, according to a new study. Photo by Mark Cowan/UPI | License Photo
May 5 (UPI) -- Intensive farming, characterized by the overuse of antibiotics, large numbers of animals and limited genetic diversity, increases the odds of animal pathogens making the jump to humans and triggering an epidemic.
When researchers in Britain analyzed the evolution of Campylobacter jejuni, a bacterium carried by cattle and the leading cause of gastroenteritis in the developed world, they found the emergence of cattle-specific strains corresponded with sharp increases in the number of cattle in the 20th Century.
Researchers at the Universities of Bath and Sheffield estimate shifts in cattle diet, anatomy and physiology enabled gene transfer between general and cattle-specific strains of the bacterium. Through accelerated gene transfer, the bacterium was able to shed unnecessary genes and acquire genes to help it cross the species barrier.
International trade and supply chains, which see animals moving all over the world, serve to heighten the public health risks associated with intensive farming.
"Over the past few decades, there have been several viruses and pathogenic bacteria that have switched species from wild animals to humans: HIV started in monkeys; H5N1 came from birds; now Covid-19 is suspected to have come from bats," researcher Sam Sheppard, professor of bioinformatics at the University of Bath, said in a news release. "Our work shows that environmental change and increased contact with farm animals has caused bacterial infections to cross over to humans too."
Sheppard and research partners hope their study -- published this week in the journal PNAS -- will motivate policy makers to more closely monitor and regulate risky farming practices. The research could also help scientists pinpoint public health risks ahead of time, so that regulators can take action to prevent new epidemics.
"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," said Dave Kelly, professor of molecular biology and biotechnology at the University of Sheffield.