Study Links Intensive Chicken Farming to Faster Spread of Diarrhoea Bacteria

A new study has found that intensive chicken farming is speeding up the spread of *Campylobacter*, the world's leading bacterial cause of diarrhoea. Researchers say the rapid growth of the global chicken population has increased the movement of the bacteria between wild birds and poultry, allowing it to evolve more quickly.

The study, published in the *Proceedings of the National Academy of Sciences*, examined nearly 2,800 bacterial genomes collected from chickens and wild birds in 30 countries between 1979 and 2024. Scientists found that the exchange of *Campylobacter* strains between chickens and wild birds has increased sharply over the past century.

Researchers also reported a rise in antimicrobial resistance, meaning some strains are becoming harder to treat with antibiotics. They say genetic changes linked to the chicken farming environment are helping the bacteria survive and spread in modern poultry production systems.

According to the researchers, global chicken numbers have risen from the 1960s to about 27 billion birds today, making chickens around 70 percent of the world's bird biomass. They warn that large-scale poultry production has created conditions that encourage the bacteria to evolve and spread more widely.

The findings have raised fresh concerns about food safety and public health, as an estimated 60 to 80 percent of *Campylobacter* infections are linked to raw chicken. The researchers say proper food handling and thorough cooking remain important in reducing the risk of infection while efforts continue to address antimicrobial resistance.