The prevalence of C. daubneyi infection in the United Kingdom has increased, but despite thepotential for rumen flukes to cause production loss in ruminant livestock, understanding of theiremergence and spread is poor. Here we describe the development of a method to explore themultiplicity of C. daubneyi infection and patterns of the parasite’s emergence and spread, based onIllumina MiSeq deep sequencing of meta barcoded amplicons of a fragment of the mt‐COX‐1 locus.Our results show high levels of genetic diversity per infection and between populations of 10 to 47 ofadult C. daubneyi, each from a total of 32 finished prime cattle consigned to slaughter from northernUnited Kingdom; with 18 unique mt‐COX‐1 haplotypes. This has implications for the adaptability ofenvironmental and intermediate host stages of the parasite to changing climatic and animalmanagement conditions, or of parasitic stages to exposure to anthelmintic drugs; potentially allowingfor greater pathogenicity, or the development of anthelmintic resistance, respectively. Our resultsillustrate the impact of high levels of animal movements in the United Kingdom, whereby multiplecommon mt‐COX‐1 haplotypes were identified in 26 populations in the absence of geographicalclustering of clades.