https://www.sciencedaily.com/releases/2020/05/200504155200.htm

An international team of researchers led by the Universities of Bath and Sheffield, investigated the evolution of Campylobacter jejuni, a bacterium carried by cattle which is the leading cause of gastroenteritis in high income countries.

The researchers, publishing in the journal Proceedings of the National Academy of Sciences, studied the genetic evolution of the pathogen and found that cattle-specific strains of the bacterium emerged at the same time as a dramatic rise in cattle numbers in the 20th Century.