Streptococcus equi subspecies equi PCR

"Strangles" is a contagious bacterial disease of horses caused by Streptococcus equi subsp. equi. Clinical manifestations include purulent nasal discharge, fever, anorexia and swollen submandibular and retropharyngeal lymph nodes which frequently form abscesses. Diagnosis has traditionally involved culture of nasal swabs, washes or pus aspirated from abscesses. While this is considered the ‘gold standard’ method, detection and confirmation of S. equi subsp. equi can take several days and identification may be complicated by the presence of other Group C β-haemolytic streptococci such as S. equi subsp. zooepidemicus and S. dysgalactiae subsp. equisimilis.

This PCR is a sensitive and rapid test compared to culture; a positive result by PCR will indicate the presence of the S. equi subsp. equi DNA in the sample (even if the bacteria are dead). Thus the PCR can still detect S. equi subsp. equi when antibiotic treatment has already commenced and this is particularly important if the culture result is negative. If a PCR positive result is returned, the recommendation is to complete the antibiotic treatment and then re-test two weeks post treatment to confirm clearance of the bacteria. Healthy horses may be tested for the absence of infection. It is important to be aware that even if the nasal samples are shown to be free of infection, the organism may still be present in the guttural pouch.

Although the primary purpose of this assay is to detect S. equi subsp. equi, the multiplex PCR will also be able to detect the presence of S.equi subsp. zooepidemicus DNA in the sample and this will be reported.

The S. equi subsp. equi PCR is not approved for export testing.




Dry swab or aspirate/lavage fluid


Sterile pot

Collection protocol:

Swab, lavage or aspirate the nasal, throat or nasopharangeal area, or nasopharangeal lavages or aspirates. Guttural pouch samples are recommended for detection of persistent infections.

Special handling/shipping requirements:

Samples should be held and transported chilled - do not freeze.