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Strangles, a disease caused by the bacterium Streptococcus equi equi, is one of the most common infections of the equine respiratory system world-wide.

Signs of strangles can include:

  • Depression
  • Loss of appetite or difficulty eating
  • Raised temperature
  • Cough
  • Nasal discharge
  • Swollen glands in the throat region
  • Rupture of glands with abscess material (pus)
  • Difficulty breathing

Symptoms in affected horses can vary widely, so if your horse begins to show signs of becoming unwell it is essential that you seek veterinary advice. Mild symptoms may be mistaken for other respiratory diseases such as a dust allergy or viral infection, but compromised horses showing nothing more than a mild nasal discharge will play a significant role in spreading disease, and may still go on to develop complications.


Often we will make a presumptive diagnosis on history and clinical signs alone. Typically, we will then use an endoscopic camera or a sequence of throat swabs to confirm the diagnosis while providing biosecurity advice which must be adhered to scrupulously in order to prevent further spread of disease.

Contrary to popular belief, there is no blood test which can directly diagnose strangles. We are however able to test for recent exposure to the Strangles organism. The test comes with significant limitations, so please discuss with the treating vet the most appropriate test for your circumstances.

Unlike equine influenza, strangles is not airborne – but it can spread quickly through either direct contact between horses or indirect contact such as shared tack, drinking facilities, handlers and even yard dogs and cats. The incubation period of disease is anything from 3-14 days.

What to do in an outbreak

Don’t panic! Veterinary advice and oversight is essential, as your circumstances will be unique, but broadly speaking – once the first case of strangles on a yard has been diagnosed, all other horses are at risk:

  • Isolate the affected horse(s)
  • Close the yard to new arrivals. Horses should not be moved from the yard, even if they appear healthy
  • All healthy animals on the yard should be monitored closely to pick up new cases of strangles as early as possible. Monitor rectal temperatures twice daily

It is useful to move horses into three distinct groups based on risk:

  • Red group – horse(s) known to be affected
  • Amber group – horses that have in some way been in contact with the red group and are therefore at elevated risk – for example, stabled close by or turned out together or in otherwise close contact
  • Green group – no known exposure to either of the other groups of animals

This approch limits the spread of disease once it is known to be present. Equipment (forks, feeding buckets, rugs etc.) and staff should not move between groups. Horses showing signs of disease or a raised temperature should be moved into the red group. Engaging veterinary help early will reduce the costs and time involved in the ’clean up’ procedure after an outbreak.

Treatment usually revolves around supportive care, good stable management and hygiene. Antibiotics are rarely used.


Ensure everyone on the yard is kept informed and behaves appropriately. People who are in regular contact with horses from outside the yard should stay away from the infected premises. Use disinfectant foot dips and wear protective clothing and gloves when handling ‘red group’ horses.

An outbreak can mean a lengthy period of closure for a yard.


  • Many yards will now insist on a recent negative strangles exposure blood test before admitting new liveries. This is a good start, however, as the blood test is limited and will not in any case pick up other infectious problems, a period of quarantine for new arrivals is still recommended (use the opportunity to attend to other requirements such as vaccination and worming)
  • Avoid sharing tack or equipment with horses with an unknown health state
  • Design your biosecurity plan BEFORE disease strikes

Further reading

  • The Animal Health Trust’s STEPS (‘Strategy To Eradicate and Prevent Strangles’) protocol is the gold standard advice to have on hand when dealing with disease. Click here to download in PDF form.