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Equine Strangles

Fátima Cruz
September 29th, 2015

Identification of carriers of Streptococcus Equi

Identificación de portadores de Streptococcus Equi
Retropharyngeal lymph node abscess caused by Streptococcus equi subsp. equi.
Dr. Andrew Waller (Animal Health Trust, Reino Unido), British Horse Society Scotland, STEPS (Strategy To Eradicate and Prevent Strangles)

Streptococcus equi (S. equi) is the bacterium that causes equine strangles. Some horses are carriers of S. equi, meaning that they are infected with S. equi but do not show any signs of the disease. These horses can be a source of S. equi for other (susceptible) horses. Young horses (weaning foals, yearlings and two-year-old horses) are particularly susceptible to this disease; however, strangles can affect horses of any age.

Strangles outbreaks occur due to the movement of horses or the introduction of carriers in a population of susceptible horses. Therefore, the identification and treatment of strangles carriers eliminates the possibility of having potentially infectious horses and can significantly reduce the probability of having an outbreak in a yard or stud farm.

S. equi carriers normally harbour the bacterium in the gutural pouches, which can be inflammed. However, in some cases the inflammation may not be visible and S. equi can form a thin and invisible layer of bacteria (biofilm).

Which horses and when to test?

Identificación de portadores de Streptococcus Equi
Streptococcus equi subsp. equi condroid located in the guttural pouch.
Dr. Andrew Waller (Animal Health Trust, Reino Unido)

Sampling for Strangles diagnosis

Nasopharyngeal swab

Collection of samples in horses using a nasopharyngeal swab

Toma de muestras Streptococcus Equi Lavado de bolsas guturales
Endoscopy and wash of the guttural pouches in a carrier of Streptococcus equi subsp. equi.
Dr. Jamie Gartside (Tay Valley Vets, Reino Unido), British Horse Society Scotland, STEPS (Strategy To Eradicate and Prevent Strangles)

Guttural pouches washes

In those horses with a positive result in a nasopharyngeal swab, or in those cases where the carrier status needs to be ruled out, the endoscopic examination and wash of the guttural pouches is essential.

Method of collection for guitural pouch washes:

  1. Pass the endoscope through the central nasal meatus of the same side of the head as the guttural pouch to be sampled to the level of the common pharynx. The openings of the guttural pouches are visible as mucosal flaps on both sides of the pharynx.
  2. Pass the biopsy forceps or a similar guide instrument through the biopsy chanel and under the flap of the guttural pouch and extend the endoscope into the pouch. Slightly twisting the endoscope helps to introduction into the pouch.
  3. Once into the pouch, make a thorough inspection of all parts and later replace the guide instrument in the biopsy chanel with a sterile catheter.
  4. Ensure the head of the horse is elevated before the instillation and aspiration of approximately 50 ml of sterile saline into the pouch from a syringe attached to the catheter.
  5. The entire wash should be placed in a leak-proof universal container which should be labelled with the name of the horse and the origin of the aspirate (right or left guttural pouch).

The wash should be sent to the laboratory as soon as possible (it should arrive to the laboratory in less than 48 hours) and should be accompanied by the corresponding submission form.

Serology - S. equi ELISA

This test identifies horses that have been exposed to S. equi in the past 6 months and therefore have developed antibodies against protein M of S. equi (SeM).

For further information and the consultation of questions regarding the diagnosis, treatment or control of an outbreak of strangles:

Fátima Cruz

Equine Health Surveillance Unit
VISAVET Health Surveillance Centre
Complutense University Madrid (Spain)

Tel.: (+34) 913943999


Article data

Equine Strangles
Fátima Cruz
Online publication date:
September 29th, 2015

Author data
Fátima Cruz
Dra. Fátima Cruz
Equine Health Surveillance

VISAVET Health Surveillance Centre
Complutense University
Madrid (Spain)

Related articles

1 Strangles: Taking steps towards eradication

2 Naturally occurring persistent and asymptomatic infection of the guttural pouches of horses with Streptococcus equi

3 Combining two serological assays optimises sensitivity and specificity for the identification of Streptococcus equi subsp. equi exposure

4 Streptococcus equi infections in horses: guidelines for treatment, control, and prevention of strangles

5 Elimination of guttural pouch infection and inflammation in asymptomatic carriers of Streptococcus equi

6 Getting a grip on strangles: recent progress towards improved diagnostics and vaccines

7 Detection of Streptococcus equi subspecies equi using a triplex qPCR assay

More information

1. Strategy to eradicate and prevent Strangles (STEPS)

2. Equine Strangles

3. HBLB Codes of Practice 2015