Research published by a UK consortium marks a further leap forward towards combatingthe plague of the horse world – strangles – and other diseases ofanimals.

The consortium (including the Animal Health Trust, the University of Cambridge and the Wellcome Trust Sanger Institute) has solved the DNA sequences of Streptococcus equi – the causative agent of strangles, and Streptococcus zooepidemicus , a versatile relative that causes a range of diseases in animals, including horses and dogs, and occasionally humans.

A strangles abscess According to the consortium, these DNA sequences shed new light on how these bacteria cause disease. They also highlight many new areas for developing better diagnostic tests, therapies and preventive vaccines.

Andrew Waller, head of bacteriology at the AHT, said: “The publication of these genomes in PLoS Pathogens is the culmination of over seven years of research. We are extremely excited about their implications for future international research towards improving animal and human health.”

The research, funded by The Horse Trust and the Horserace Betting Levy Board (HBLB), has already enabled the AHT to develop DNA and blood tests to diagnose strangles. It is now concentrating its efforts on developing safe and effective vaccines against strangles and the many diseases caused by S. zooepidemicus .

Horse Trust chief executive Paul Jepson said: “The news that the research we funded has not only resulted in reducing the distress caused by strangles, but will now also help to prevent diseases in horses and other animals is brilliant. We’re delighted to be involved in this world-leading scientific research, from which we are already seeing such positive results.”

Professor Willie Donachie, chairman of the HBLB’s veterinary advisory committee said: “ S. zooepidemicus causes a host of diseases in horses that affect their health and welfare. This research is an important contribution towards the prevention, diagnosis and treatment of inflammatory airway disease, upper respiratory disease and abortion in equines. Reducing the impact of S. zooepidemicus on the training, racing and breeding of Thoroughbreds will be a significant benefit to horseracing.”

S. equi evolved from S. zooepidemicus , which is usually harmless. However, S. zooepidemicus is opportunistic and can cause respiratory disease and abortion in horses, acute fatal haemorrhagic pneumonia in dogs and mastitis in cattle, goats and sheep.

A strangles pony in isolation Surprisingly, S. equi has, in its enhanced arsenal of biological weapons, genes that are very similar to those found in a type of Streptoccocus that causes pharyngitis, toxic shock syndrome, impetigo and scarlet fever in humans: the S. equi sequence will also help with those human studies.

Dr Matthew Holden, leader of the analysis team at the Wellcome Trust Sanger Institute, claims that the genomes show weaknesses in S. equi . He said: “ S. zooepidemicus and S. equi are brothers in arms who share a common ancestry but, while acquiring some genes, S. equi has been discarding others it no longer needs. The makings of this pathogen may very well be its undoing: it has lost functions found in its more versatile relatives, and consequently finds itself backed into a corner.

“With the new improved diagnostics, and the prospect of an effective vaccine round the corner, eradication becomes a real possibility.”


The following organisations were involved in the work to solve the DNA sequences of Streptococcus equi and Streptococcus zooepidemicus :

  • Animal Health Trust
  • Imperial College London
  • University of Cambridge
  • University of Oxford
  • University of Newcastle upon Tyne
  • Wellcome Trust Sanger Institute
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