Streptococcus equi (S. equi) is a Group C Lancefield Streptococcus and is the main causative agent for the horse respiratory disease strangles. The current mortality rate of strangles is around 1 % but this can increase upon the development of ‘bastard strangles.’ Strangles is a highly contagious disease which spreads via direct contact between infected horses normally through sharing water buckets, stables and grooming equipment.

The main objective of this project was to isolate and develop a phage cocktail that could be used to treat S. equi infections as current treatment with antibiotics is physiologically difficult. Strangles accounts for around a third of all equine based diseases worldwide which emphasises the importance of this work due to the financial burden of this disease and the sentimental associations.

Phages were isolated from manure and water samples collected from a range of geographically discrete locations around the UK including Suffolk, Essex, Tyne and Wear, Perth and Kinross. Isolated phages where enriched and assessed for killing efficacy on a well characterised panel of 22 S. equi strains (provided by the Animal Health Trust). A large cross-infection study was undertaken to determine the host range for each phage. A large cross infection experiment involving temperate bacteriophages induced from the bacterial chromosome with Norfloxacin (DNA Gyrase inhibitor) was also undertaken.

5 lytic and 15 temperate bacteriophages were isolated which targeted a subset of the S. equi isolates and these bacteriophages were subjected to genome sequencing at NU-Omics facility at the University of Northumbria at Newcastle, UK. This work has shown that potentially bacteriophages of S. equi could be utilised to develop an effective phage cocktail that could be used to treat horses topically or through ingestion via water/food samples.