Horse Side Vet Guide ®

Equine Health Resource

Strangles

Synonyms: Horse Distemper, Streptococcus Equi Upper Airway Infection

Strangles is a common and highly contagious bacterial infection of the upper airway caused by the bacteria Streptococcus equi. Signs of disease are coughing, yellow nasal discharge, but most characteristically the development of large abscess swellings and yellow pus drainage from under and/or behind the jaw.

In rare cases these swellings can become so large that they compress the windpipe Infection between horses occurs from the spread of an infected horse’s nasal discharge or the pus that is draining from an abscess. this is where the name comes from.

It is spread horse to horse, through direct contact or contact with drainage from an infected horse.

Diagnosis- It is easy for vets (and experienced horse people) to presumptively diagnose a classic case of Strangles. There are few equine diseases that are as familiar and so obvious in their signs. On the other hand, there are other diseases that can mimic it, and it can take some unusual forms too, so DEFINITIVE diagnosis requires definite identification of the organism in the laboratory. Going for a definite diagnosis is wise because once the organism is identified, there will be a great effort made to prevent infection of other horses. If the agent is confirmed as another bacterial species, that effort may not be needed.

Treatment- Most cases of Strangles resolve on their own. Ultimately the abscesses burst, and drainage occurs and the swelling decreases. The veterinary goal is to prevent spread to other horses and to maximize patient health and comfort. The key to that is helping the abscesses drain.

Prognosis & Relevant Factors

The prognosis for Strangles is generally good with prompt treatment. The severity of infection depends to a great extent on the degree of immunity. It is highly contagious, but the mortality rate is very low.

Most cases of Strangles are unsightly but uncomplicated, and resolve with time and some basic treatment. The key to treatment is drainage of abscesses. Antibiotics are usually not necessary and can in some cases complicate recovery.

However, a small number of horses that acquire Strangles get internal abscesses, which can show up anywhere in the body, most commonly in the abdomen. Very rarely, abscesses can form in the brain, joints and other location. The prognosis for these horses is poor. There is more on that in the Bastard Strangles FAST FACT.

QUESTIONS TO ASK MY VET

  • Does culture need to be performed to be sure that this is Strangles?
  • How can I minimize the development of disease in my other horses?
  • PREVENTION

    By keeping your horse's general health as good as it can be you reduce the severity of this disease. Maintain excellent general health through the best husbandry and nutrition. Reduce exposure to Streptococcus equi, by placing new horses in quarantine for 4-6 weeks, if possible. Discuss the risks and benefits of vaccination with your vet. There is advantage in some cases, but controversy over the effectiveness and safety of some of the vaccines.
    Author: Doug Thal DVM Dipl. ABVP

    RELATED REFERENCES

    Higgins AJ, Snyder JR eds. The Equine Manual. 2nd Ed. Edinburgh: Elsevier Saunders 2006.

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