Factory-farmed chicken has led to more than a 100-fold increase in a common disease that causes food poisoning, a study has suggested
More than a billion chickens are produced and slaughtered for meat each year in the UK
Researchers have found industrial farming, and in particular densely populated chicken flocks, has allowed strains of a bacterium called Campylobacter that once circulated in wild birds to mix extensively in commercial poultry populations
Campylobacter is the most common bacterial cause of diarrhoea worldwide, causing more than 3.5 times as many gastroenteritis cases in the UK each year than all other monitored foodborne bacteria combined.
Rising rates of antimicrobial resistance, in which bacteria resist drugs designed to kill them, are making Campylobacter infections increasingly difficult to treat
Sam Sheppard, professor of microbial genomics and evolution at the University of Oxford, said: “Industrial farming has created one of the largest animal habitats on the planet. Our findings provide new evidence that human-driven environmental change can increase the spread of infectious diseases
“As chicken populations have grown, bacteria that were once largely confined to wild birds have gained far more opportunities to enter poultry flocks, spread and become established. Understanding these evolutionary consequences is essential if we are to reduce future risks from zoonotic disease and antimicrobial resistance.”
For the study, published in the journalProceedings of the National Academy of Sciences, researchers analysed nearly 2,800 bacterial genomes collected from chickens and wild birds in 30 countries, including the UK and the US, between 1979 and 2024
They found the huge global expansion of chicken farming has created ideal conditions for the bacterium to spread, mix and acquire new traits that help it survive
Since the 1960s, global chicken numbers have increased seven-fold to approximately 31 billion birds. This increase has not just made meat more affordable globally, but also allowed for genetic changes in Campylobacter
Researchers suggest vast, densely populated chicken flocks may act as ecological “pathogen sponges”, absorbing and amplifying bacterial strains from multiple
Mathematical modelling showed that once chicken populations reach a critical scale, strains originating in wild birds can become self-sustaining within poultry populations
A previous study from Ineos Oxford Institute for Antimicrobial Research found 80 per cent of human Campylobacter infections in Oxfordshire are associated with poultry meat, and many of these infections are resistant to antibiotics
“Understanding how farming practices influence bacterial evolution is an important step towards reducing the burden of foodborne disease,” study author Oakem Kyne said
Campylobacter infections are generally mild, according to the World Health Organization (WHO), but the bacteria can cause fatal infections among young children, the elderly and immunosuppressed individuals
The bacteria, which can cause diarrhoea, abdominal pain, fever, headache, nausea and vomiting, can be killed by thoroughly cooking food. That’s because it spreads
According to the WHO, if you catch the disease, treatment is not usually required, but replacing electrolytes and staying hydrated is advised
