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Strangles: What's the Deal?

What is Strangles: A bacterial infection caused by Streptococcus Equi subsp. Equi

Current outbreak: Includes Pierce, Stevens, Pasco, Thurston, Spokane, Snohomish, and Franklin counties in WA according to the Equine Disease Communication Center.

What does is look like: Can include some or all of the following symptoms

  • Fever**

  • Nasal discharge**

  • Swollen lymph nodes**

  • Difficulty swallowing and/or breathing

  • Swelling of the throat latch region if severe

  • Can cause internal abscesses

Incubation time: Usually 3-14 days from exposure

Typical duration: Average course of disease is 23 days

Diagnosis: Culture or PCR detection on nasal swab, nasopharyngeal wash or guttural pouch wash. Nasal shedding of strangles usually occurs 2-3 days after the onset of fever and can last several weeks. Minimum of 3 consecutive nasal washes 1-2 weeks apart with negative results needed to confirm absence of infection/shedding.

Carrier State: Some horses can become carriers of Strangles by developing chondroids after being infected. These horses can carry the organism for YEARS.


  • Practice good biosecurity: limit nose-nose contact with other horses when traveling, limit others from petting/feeding your horse when traveling/showing, wash your hands frequently, etc. Quarantine new horses to a facility for a minimum of 4 weeks (horses can continue to shed the bacteria for weeks after recovery of clinical signs).

  • Vaccination: The vaccine is NOT 100% effective in preventing strangles. However, horses who are vaccinated typically experience a less severe form of the disease.

  • It is important NOT to vaccinate your horse during an outbreak as elevation of the horses’ antibody levels if they’ve already been exposed is dangerous too and can lead to an immune mediated vasculitis called Purpura Hemorrhagica where your horse may slough skin over its limbs or have other organs affected (kidney failure, pneumonia, cardiac arrhythmias) and even lead to death.

Quarantine and biosecurity measures to be used in an outbreak are outlined on the eighth page.

Other sources consulted for this post: Equine Internal Medicine, Third Edition by Stephen M.Reed, Warwick M. Bayly and Debra C. Sellon published in 2010.

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