Delaware Department of

Disease Information

Strangles (Streptococcus equi)

Strangles is a bacterial infection caused by Streptococcus equi. While the disease is common, with most horses exposed and/or infected at a young age, it is considered to be highly contagious. The incubation period is from 3 to 14 days.

What are the signs and symptoms of Strangles in horses?

  • Fever >101.5°F, usually preceding other clinical signs by 24 – 28 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
  • Cough

How is Strangles spread?
Strangles is spread from horse to horse through direct contact or from contact with a contaminated surface, including contaminated clothing of caretakers, shared water and feed buckets, and equipment. S. equi is present during the incubation period and the horse can be a carrier without any clinical signs. Horses who have been infected but are clinically healthy can continue to incubate and shed S. equi. A recovered horse may be a potential source of infection for at least six weeks after the clinical signs have disappeared. After recovery, it is possible that some horses will become long-term, periodic shedders of the bacteria that can cause new outbreaks.

Horse owners, trainers, and staff should practice good biosecurity to help prevent the spread of this infectious disease. These measures include:

  • Any horses displaying clinical signs compatible with strangles including, but not limited to, fever > 101.5◦F, nasal discharge, cough, submandibular swelling, lethargy, and inappetence, should contact their veterinarian and isolate suspect horses at least 50 yards away from other horses.
  • Do not share water, feed, or equipment with other horses.
  • Wash hands in between handling horses with soap and water to prevent spreading infectious agents.
  • Sanitize equipment using a 10 percent bleach in water (or other effective disinfectant) to kill bacteria and viruses.
  • Shower prior to and wear freshly laundered clothes and clean shoes (not worn at a farm), when presenting to any other equine premises for work.

What to do if you suspect Strangles on your farm?
Immediately contact your veterinarian. Your veterinarian will need to make a diagnosis through culture or PCR testing to confirm the disease. You should isolate the suspected horse(s) at least 50 yards away from other horses to prevent contact. Continue to practice the biosecurity measures listed above.

Equine Disease Communication Center: Streptococcus Equi (Strangles) Disease Factsheet

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