Strangles: A guide for horse owners

Strangles is a highly infectious bacterial disease caused by Streptococcus equi subspecies equi (commonly abbreviated as Strep. equi), affecting horses of all ages. It spreads quickly and can cause severe illness, making early detection and management critical.

Horses infected with strangles may show the following symptoms: 

  • Depression or dullness 
  • High temperature (fever) 
  • Loss of appetite 
  • Thick nasal discharge (purulent) 
  • Laboured breathing 
  • Soft, moist cough 
  • Painful, swollen lymph nodes around the throat (typically seen seven days after fever onset) 
  • Difficulty breathing or swallowing in severe cases (the "strangles") 

Note: Even mild cases are highly infectious.

The bacteria spreads through: 

  • direct contact with infected horses 
  • contaminated equipment (troughs, feed bins, halters, saddlery) 
  • handlers (via clothing, footwear and hands) 
  • infected nasal and oral secretions.

Clinical signs appear 3-14 days after exposure. Horses begin shedding bacteria from their nose 4-7 days after exposure, but not within the first 24 hours of fever. This means you have 24 hours to isolate sick horses and prevent spread.

Note: Some horses may become asymptomatic carriers, shedding bacteria for weeks to months.

Strep. equi is present in the mucus from the nose and mouth of infected horses. It doesn’t survive long in the environment (hours to days), but indirect transmission via contaminated equipment or water sources is common. Horses typically become infected through direct contact, but asymptomatic carriers can cause unexpected outbreaks when moved to new properties.

You can take the following steps to reduce the risk of an outbreak.

  • Vaccination: While not 100% effective, vaccination can reduce the severity of disease. Consult your veterinarian for advice, as frequent boosters are required.
  • Good hygiene: Regularly disinfect equipment and practise thorough handwashing after handling horses.
  • Separation: Keep infected and healthy horses at least five meters apart to prevent airborne transmission.
  • Vigilance: Monitor for signs of illness and contact your vet promptly if you suspect strangles.
  • Isolation: Sick horses should be isolated immediately to limit spread.

If strangles is suspected: 

  • Isolate symptomatic horses immediately.
  • Contact your veterinarian for diagnosis and management advice. Laboratory confirmation via swabs or blood samples is crucial.
  • Monitor temperatures regularly with a thermometer for early detection.
  • Use Personal Protective Equipment (PPE), including:
    • disposable gloves
    • hand sanitizer
    • rubber boots that can be washed and disinfected
    • protective outer clothing (eg overalls) that can be laundered thoroughly.
  • Disinfect all equipment and clothing after contact with infected horses.
  • Test horses post-recovery to ensure they are not carriers before moving them off the property.

  • Abscesses usually burst naturally. In severe cases, a veterinarian may need to lance them.
  • Antibiotics are generally not required unless prescribed by a vet during active outbreaks to prevent abscess formation.
  • Most horses recover with supportive treatment. In rare cases, complications like 'bastard strangles' (infection spreading to other lymph nodes) can occur, which may be fatal without intervention.

When to call your vet

Always consult your veterinarian for advice on diagnosis, treatment and outbreak control measures.

Stay informed, stay vigilant, and work closely with your veterinarian to protect your horses from strangles.

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