Molecular epidemiology of Streptococcus zooepidemicus isolated from the respiratory tracts of Thoroughbred racehorses in training.

The research article investigates the molecular characteristics of the bacterium Streptococcus zooepidemicus, found in the respiratory systems of Thoroughbred racehorses in Newmarket training yards. It explores the diversity and prevalance of various types of the bacterium, pointing out potential challenges in developing effective vaccines against it.

Objective of the Study

• The primary objective of the study was to examine the molecular epidemiology of Streptococcus zooepidemicus (S. zooepidemicus) that was isolated from the respiratory tracts of 198 Thoroughbred racehorses.
• The horses were all from three different training yards located in Newmarket and the research was carried out over a 10-month period.

Methodology

• To classify the type of S. zooepidemicus, researchers used two separate PCR (Polymerase Chain Reaction) procedures.
• These PCR procedures targeted the M-like protein hypervariable region and the 16S-23S RNA gene intergenic spacer regions of the bacteria.

Results of the Study

• S. zooepidemicus was isolated in 23% (224 out of 983) of the study samples. The bacteria was not of the same type; 24 different types were identified in varying prevalance.
• Out of these different types, four (A1HV4, A1HV2, C1HVu, and D1HV1) were found to be the most common and they accounted for 45% of all the types of isolates.
• In similarity with a preceding research conducted on Welsh Mountain ponies, S. zooepidemicus was confirmed not to be a homogeneous clonal population in horses, but instead represented a wide diversity of strain types.

Implications of the Findings

• This wide range of S. zooepidemicus strains indicate potential challenges in controlling infections in horses through vaccination.
• Given the diverse strain types, it is probable that the development of a protective immunity against the bacteria may require the induction of a heterogeneous, cross-protective response.