Streptococcus equi

What is Strangles? 

The upper respiratory disease commonly referred to as strangles is caused by Streptococcus equi subsp equi. Strangles is spread from horse to horse through direct contact. Horses can also contract the disease by coming into contact with contaminated surfaces. The disease is highly infectious.

Clinical Signs: The incubation period for Strangles is 3 to 8 days, at which point the following clinical signs may appear: 

  • Fever, usually preceding other clinical signs by 24-48 hours 
  • Abscesses in the mandibular lymph nodes (in the throatlatch and below the jaw)
  • Nasal discharge: often thick white and yellow mucus 
  • Inflammation of the throat • Difficulty swallowing 
  • Wheezing
  • Coughing 

Purpura hemorrhagica is a vasculitis which can be caused by Streptococcus equi. It results in bleeding which causes red spots on the mucous membranes and swelling of the limbs and head (rare; only in cases with complications)

Diagnosis: Diagnosis is made through culture of nasal wash, nasal swab, or pus aspirated from abscesses or through PCR testing. 

Treatment: Supportive care is the primary treatment. Use of antibiotics in infected horses is restricted to those with severe clinical signs such as respiratory difficulty as most horses recover without antibiotic treatment. Horses treated with antibiotics early in the course of infection may avoid lymph node abscesses but may not develop immunity to the disease. Treatment decisions should be made by a veterinarian.

Prevention: An intranasal vaccine is available but is not effective against all infections. Any surfaces that are contaminated with mucus or other nasal discharge from infected horses pose a threat of infection to healthy horses. Affected horses should be isolated and increased  biosecurity practiced.


May 20, 2024
Newaygo County, MI
Confirmed Case(s) - Voluntary Quarantine
May 18, 2024
Emmett County, MI
Confirmed Case(s) - Voluntary Quarantine
May 18, 2024
St Clair County, MI
Confirmed Case(s) - Voluntary Quarantine