New research from the University of Oxford reveals how industrial poultry farming has dramatically increased campylobacter bacteria, raising concerns about food safety and antimicrobial resistance
Scientists have uncovered a troubling connection between industrial poultry farming and the rapid spread of campylobacter the leading cause of bacterial diarrhea worldwide. This alarming trend, which has seen the bacteria’s prevalence increase more than 100-fold is directly linked to the global expansion of chicken farming operations.
The study, conducted by researchers at the Ineos Oxford Institute and the University of Oxford analyzed nearly 2,800 bacterial genomes collected from chickens and wild birds across 30 countries between 1979 and 2026. Their findings highlight how modern farming practices have created ideal conditions for campylobacter to evolve and spread.
Global poultry expansion fuels bacterial evolution
The researchers found that the seven-fold increase in global chicken populations since the 1960s – now totaling approximately 31 billion birds – has allowed bacteria from wild birds to circulate within poultry populations. This massive expansion has created what the scientists describe as ecological “pathogen sponges,” where large, densely populated chicken flocks absorb and amplify bacterial strains from multiple sources.
Through genomic analysis, the team identified specific genetic changes in campylobacter that have helped it adapt to modern farming environments. These adaptations include genes associated with antimicrobial resistance making infections increasingly difficult to treat. The study also revealed that once chicken populations reach a certain scale, strains originating in wild birds can become self-sustaining within poultry populations.
Evolutionary consequences of farming practices
Sam Sheppard, professor of microbial genomics and evolution at the University of Oxford and senior author of the study, emphasized the broader implications of these findings: “Our findings provide new evidence that human-driven environmental change can increase the spread of infectious diseases. Understanding these evolutionary consequences is essential if we are to reduce future risks from zoonotic disease and antimicrobial resistance.”
The research suggests that as campylobacter strains adapt to life in poultry, they acquire traits that help them survive in challenging environments. Oakem Kyne, a researcher at the University of Oxford and first author of the paper, noted that “understanding how farming practices influence bacterial evolution is an important step towards reducing the burden of foodborne disease.”
The growing threat of antimicrobial resistance
One of the most concerning aspects of this research is the connection between industrial farming and the rise of antimicrobial resistance. The study found that 80% of human campylobacter infections in Oxfordshire were associated with poultry meat, with many strains showing resistance to antibiotics. This trend is particularly worrying given that chickens now account for around 70% of all bird biomass on earth.
Mathematical modeling from the study demonstrated how large-scale chicken farming creates conditions where bacterial strains can thrive and evolve. The researchers warn that without changes to current farming practices, we may see continued increases in foodborne illnesses and more difficult-to-treat infections.
The findings underscore the need for a better understanding of how agricultural practices influence bacterial evolution. As our food systems continue to evolve, so too will the microorganisms that thrive within them, presenting ongoing challenges for food safety and public health.
