Study Links Industrial Poultry Farming to Increased Spread, Adaptation of Campylobacter
A new genomic study has linked the global expansion of industrial poultry farming to a more than 100-fold increase in the movement of Campylobacter strains, enabling bacteria historically associated with wild birds to circulate and mix extensively within commercial chicken populations.
Published in the Proceedings of the National Academy of Sciences, the study was conducted by researchers from the Ineos Oxford Institute for Antimicrobial Research. The researchers analyzed nearly 2,800 Campylobacter genomes collected from chickens and wild birds in 30 countries, including the U.S. and UK, between 1979 and 2024.
Campylobacter is a major bacterial cause of diarrheal illness worldwide. According to the researchers, rising antimicrobial resistance (AMR) among Campylobacter is also making infections increasingly difficult to treat.
Expansion of Poultry Production Created Opportunities for Campylobacter Spread
Since the 1960s, the global chicken population has increased sevenfold to approximately 31 billion birds, and chickens now account for around 70 percent of global bird biomass.
The researchers found that the expansion of chicken farming created conditions that enabled Campylobacter strains to spread, mix, and acquire traits that could improve their survival in poultry production environments.
Using genomic analysis, the researchers identified genetic changes associated with Campylobacter adaptation to chickens. These included genes involved in AMR, oxidative stress tolerance, metal acquisition, and motility.
“Industrial farming has created one of the largest animal habitats on the planet,” said Sam Sheppard, Ph.D., Professor of Microbial Genomics and Evolution at the University of Oxford and senior author of the study. “Our findings provide new evidence that human-driven environmental change can increase the spread of infectious diseases.”
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According to Dr. Sheppard, as chicken populations have grown, bacteria that were previously largely confined to wild birds have had more opportunities to enter poultry flocks, spread, and become established.
Large Poultry Populations May Act as ‘Pathogen Sponges’
The study suggested that large, densely populated chicken flocks may act as ecological “pathogen sponges,” absorbing and amplifying bacterial strains originating from multiple sources.
Mathematical modeling showed that when chicken populations reached a critical scale, strains originating in wild birds could become self-sustaining within poultry populations, even when the strains were poorly adapted to chickens.
A previous study conducted by the Ineos Oxford Institute, the UK Food Standards Agency (FSA), and other collaborators found that 80 percent of human Campylobacter infections in Oxfordshire, England were associated with poultry meat, and that many of the infections were resistant to antibiotics.
“As Campylobacter strains adapt to life in poultry, they can acquire traits that help them survive in challenging environments, including traits linked to antimicrobial resistance,” said Oakem Kyne, a D.Phil. student at the University of Oxford and first author of the study.
The researchers asserted that understanding how intensive poultry farming influences bacterial evolution could help inform efforts to reduce the burden of foodborne disease, zoonotic disease, and AMR.
