Strangles diagnostic testing and outbreak control

Strangles diagnostic testing and outbreak control:
Centre for Equine Infectious Disease (Melbourne University)


  • Strangles is caused by Streptococcus equi (S. equi).
  • Strangles is the most frequently diagnosed infectious diseases of horses world-wide.
  • In Victoria strangles is a notifiable disease under the Livestock Disease Control Act 1994, and must be reported within seven days.

Diagnostic testing

  • Antibody testing: (Please call James Gilkerson 03 83449969, or Nino Ficorilli 03 8344 7370). CEID currently offers an ELISA test (developed at the Animal Health Trust in the UK) to determine if horses have been recently exposed to S. equi. Requires two blood samples collected 10-14 days apart.
  • Bacteriological testing: (Please call J Gilkerson 03 83449969, or N Ficorilli 03 8344 7370). CEID currently offers bacteriological culture from nasal swab, naso-pharyngeal swab, guttural pouch lavage, or nasal lavage samples to detect infectious S. equi. Polymerase chain reaction testing (developed at the Animal Health Trust in the UK) to detect the presence of S. equi DNA will be available by Christmas 2015. Aspiration of pus from an unburst, abscessed lymph node is the sample of choice from which to culture to make the initial microbiological diagnosis.

Clinical signs of strangles

  • Include fever, loss of appetite, depression, coughing, thick nasal discharge and pain, swelling and abscess formation in the lymph nodes under the jaw and in the throat region.
  • Not all horses in an outbreak will develop all of these clinical signs.

Treatment of cases of strangles

  • Primarily supportive therapy.
  • Includes nursing care and anti-inflammatory medication.

Management of strangles outbreaks

  • Strict biosecurity policies are recommended to reduce the spread of the disease, including isolation of affected horses, screening in contact horses by blood tests and determining if exposed horses are infectious by bacteriological testing.
James Gilkerson
BVSc, BSc (Vet), PhD
Professor of Veterinary Microbiology
Centre for Equine Infectious Disease

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