Studying S. equi transmission in the UK horse population

Strangles, caused by Streptococcus equi, remains endemic in the United Kingdom (UK), with ~300 laboratory diagnoses annually and subclinical long-term carriers are considered the principal drivers of endemicity. The identification of genomic changes in circulating S. equi strains provides valuable insights into pathogen adaptation and transmission. By understanding these dynamics, we aim to highlight the importance of improved biosecurity measures and other interventions which can reduce the transmission of S. equi. We hypothesised that analysis of the genomes of circulating strains could be used to provide valuable insights into the transmission of this pathogen. Our specific objectives were to determine the population structure and diversity of UK S. equi isolates and model transmission using epidemiological and whole genome sequencing data. S. equi bacterial isolates from UK clinical diagnoses of strangles were provided by laboratories participating with the Surveillance of Equine Strangles network.