Strangles

Here is a brief summary of strangles:-

A bacterial infection caused by Streptococcus equi equi (Strangles) – this causes upper respiratory tract disease but can occur in a mixed infection along with:-

• Strep. zooepidemicus
• Strep. pneumoniae
• Pasteurella
• Mycoplasma

The latter three more commonly cause lower respiratory tract disease in young horses. Signs you may see include:

• Fever
• Nasal Discharge
• Coughing
• Poor performance

To diagnose bacterial infections, we have to take a sample of fluid from the airways by endoscopy (injecting a small amount of fluid into the windpipe and sucking it back up). This is so we can see what bacteria we are dealing with, and treat it with the appropriate antibiotics.

Other treatments for respiratory disease include rest, dust free environment, drugs such as “bute” to reduce temperature, and TLC.

Strangles is best diagnosed by a naso-pharyngeal swab which is then sent to the laboratory for PCR culture although normal culture may be used.

There is also a blood test that can be used to detect any antibodies a horse may have against the strangles bacteria. However, this is an unreliable indicator of current infection because there may be a “lag phase” at the start of infection when the antibody levels are not yet increased (thereby giving a false negative) and also the antibody levels remain high for many weeks or months which may suggest that the infection is still ongoing (false positive).

There is the added complication of strangles carriers where the bacteria may survive and “be hidden” in the guttural pouches of horses for many months (or possibly years). Periodically these bacteria may be shed by the horse and possibly act as a source of infection for other horses without necessarily showing any clinical signs themselves!