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Equine Health Resource

Clostridial Myositis

Synonyms: Clostridial Myonecrosis, Gas Gangrene, Malignant Edema

This is a rare, but massive and life-threatening infection of the tissues, with the anaerobic Clostridial bacteria. The infection usually results from injection of a tissue irritating substance or from an infected wound. Poor injection technique may increase the likelihood of the condition. It has been associated with the intramuscular injection of medications, especially flunixin (Banamine). It also can be caused by puncture wounds and is a rare complication after castration.

The organism is likely carried into the tissues on the needle or within the medication. Damaged tissue provides a perfect medium for bacterial growth.

The Clostridial bacteria itself produces severe toxins that damages and kills the tissue, creating an environment for increasingly rapid bacterial growth. The toxins are very potent and also have the ability to cause signs of severe illness and shock.

Signs of this condition are a rapidly enlarging area of painful swelling, fever, depression and loss of appetite, and high heart and respiratory rates.

Diagnosis can be made by the rapidly worsening signs of disease, severe swelling, fever and illness. Definitive diagnosis requires confirmation of gas and fluid accumulation in the tissues and detection (and culture) of Clostridial bacteria in the living horse.

Treatment requires aggressive use of appropriate intravenous antibiotics, surgical opening of the infected areas and in many cases intensive care with IV fluids and other medications.

Author: Doug Thal DVM Dipl. ABVP


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


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