Abstract
BackgroundStreptococcus equi ssp. equi is the causative agent of ‘Strangles’ in horses. This is a debilitating condition leading to economic loss, yard closures and cancellation of equestrian events. There are multiple genotypes of S. equi ssp. equi which can cause disease, but to date there has been no systematic study of strains which are prevalent in Ireland. This study identified and classified Streptococcus equi ssp. equi strains isolated from within the Irish equine industry.ResultsTwo hundred veterinary isolates were subjected to SLST (single locus sequence typing) based on an internal sequence from the seM gene of Streptococcus equi ssp equi. Of the 171 samples which successfully gave an amplicon, 162 samples (137 Irish and 24 UK strains) gave robust DNA sequence information. Analysis of the sequences allowed division of the isolates into 19 groups, 13 of which contain at least 2 isolates and 6 groups containing single isolates. There were 19 positions where a DNA SNP (single nucleotide polymorphism) occurs, and one 3 bp insertion. All groups had multiple (2–8) SNPs. Of the SNPs 17 would result in an amino acid change in the encoded protein. Interestingly, the single isolate EI8, which has 6 SNPs, has the three base pair insertion which is not seen in any other isolate, this would result in the insertion of an Ile residue at position 62 in that protein sequence. Comparison of the relevant region in the determined sequences with the UK Streptococcus equi seM MLST database showed that Group B (15 isolates) and Group I (2 isolates), as well as the individual isolates EI3 and EI8, are unique to Ireland, and some groups are most likely of UK origin (Groups F and M), but many more probably passed back and forth between the two countries.ConclusionsThe strains occurring in Ireland are not clonal and there is a considerable degree of sequence variation seen in the seM gene. There are two major clades causing infection in Ireland and these strains are also common in the UK.
Highlights
IntroductionEqui is the causative agent of ‘Strangles’ in horses
Streptococcus equi ssp. equi is the causative agent of ‘Strangles’ in horses
Multi-locus typing of S. equi ssp. equi does not produce a significant advantage over single-locus typing based on seM, and studies in the UK have shown that based on the seM gene sequence analysis outbreak specific strains can be identified [4,5,6]
Summary
Equi is the causative agent of ‘Strangles’ in horses This is a debilitating condition leading to economic loss, yard closures and cancellation of equestrian events. Equi, which is a biovar of S. zooepidemicus, is the causative agent of ‘Strangles’ in horses. This devastating condition is highly contagious, has high morbidity, and can lead to stable closures. The seM gene is present in the majority of strains but, analogous to the emm genes of S. pyogenes, is highly divergent. Equi does not produce a significant advantage over single-locus typing based on seM, and studies in the UK have shown that based on the seM gene sequence analysis outbreak specific strains can be identified [4,5,6] Multi-locus typing of S. equi ssp. equi does not produce a significant advantage over single-locus typing based on seM, and studies in the UK have shown that based on the seM gene sequence analysis outbreak specific strains can be identified [4,5,6]
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