Pinning the tail of the evolution of Streptococcus equi in populations of horses and donkeys - Normandie Université
Communication Dans Un Congrès Année : 2024

Pinning the tail of the evolution of Streptococcus equi in populations of horses and donkeys

Résumé

Background: Streptococcus equi subsp. equi continues to evolve and disseminate globally causing disease and considerable economic losses. Largescale genomic analysis of S. equi and its ancestor S. zooepidemicus can be utilised to identify evolutionary events leading to the successful expansion of S. equi. Study design: Genomic analysis. Methods: 1201 S. equi sequences and 66 sequences representative of the diversity of S. zooepidemicus were used for genetic analysis. Results: A novel S. equi lineage was identified, comprising isolates from donkeys in Chinese farms, which diverged nearly 300 years ago, after the emergence of S. equi from S. zooepidemicus, but before the global sweep identified by Harris et al. [1]. Ancestral state reconstruction demonstrated that slaA, seeL and seeM were acquired by the global S. equi after the divergence of the basal donkey lineage. We identified the equibactin locus in both S. equi populations, but not S. zooepidemicus, reinforcing its role as a key S. equi virulence mechanism. Evidence of a further population sweep beginning in the early 2000s was detected in the UK. This clade now accounts for more than 80% of identified UK cases since 2016. Several sub-lineages demonstrated increased fitness, within which the acquisition of a new, fifth prophage containing additional toxin genes was identified. Main limitations: The global SARS-CoV2 pandemic meant that genomic data outside of the UK was not available after 2020. Conclusions: Acquisition of the equibactin locus was a major determinant in S. equi becoming an equid-exclusive pathogen, but that other virulence factors were fixed by the population sweep at the beginning of the 20th century. Evidence of a secondary population sweep in the UK and acquisition of further advantageous genes implies that S. equi is continuing to adapt and therefore continued investigations are required to determine further risks to the equine industry. Ethical animal research: Not required: analysis of microorganisms. Informed consent: Not applicable. Competing interests: A. Waller is CSO at Intervacc AB. Funding: Petplan Charitable Trust grant: S19-741-780. Reference: [1] Harris, SR, Robinson, C, Steward, KF, Webb, SK, Paillot, R, Parkhill, J, Holden, MTG, Waller, AS. Genome specialization and decay of the strangles pathogen, Streptococcus equi, is driven by persistent infection. Genomic Res. 2015;25:1360–1371. 10.1101/gr.189803.115.
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hal-04723315 , version 1 (07-10-2024)

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Hayley Wilson, Andries J. van Tonder, Christopher Ruis, Noémie Lefrancq, Abigail McGlennon, et al.. Pinning the tail of the evolution of Streptococcus equi in populations of horses and donkeys. 12th International Equine Infectious Diseases Conference, Sep 2024, Deauville, France. pp.23 (n°20), ⟨10.1111/evj.14215⟩. ⟨hal-04723315⟩
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