An international team of researchers led by the Universities of Bath and Sheffield has investigated the evolution of Campylobacter jejuni , a bacteria carried by cattle that is the leading cause of gastroenteritis in high-income countries .
Their study has concluded that the overuse of antibiotics, high numbers of animals, and low genetic diversity caused by intensive farming techniques increase the likelihood that pathogens will become a major public health risk .
Genetic evolution of the pathogen
The study , published in the Proceedings of the National Academy of Sciences , focuses on the genetic evolution of the pathogen , finding that livestock-specific strains of the bacteria emerged at the same time as a significant increase in livestock numbers in the 20th century.
Specifically, changes in cattle diet, anatomy and physiology triggered gene transfer between general and specific strains of cattle with significant gene gain and loss.
This helped the bacteria infect humans : In recent decades, there have been several pathogenic viruses and bacteria that have changed from wild animal species to humans: HIV started in monkeys; H5N1 came from birds; Covid-19 is now suspected of originating from bats.
For the infection to be a pandemic, other factors that are already common are added, such as the movement of animals worldwide and intensive agricultural practices.
According to Sam Sheppard of the Milner Center for Evolution at the University of Bath:
There are an estimated 1.5 billion cattle on Earth, each of which produces around 30 kg of manure every day; if about 20 percent of them carry Campylobacter , that amounts to a huge potential public health risk.
Campylobacter is estimated to be present in the faeces of 20% of livestock worldwide . It should be remembered that Campylobacter causes three times more cases than E. coli, Salmonella, and listeria combined.