Clostridial Myositis

This disease is life-threatening and should be treated by a veterinarian swiftly.

Clostridial myositis is a rare but serious bacterial infection, which causes inflammation and death of muscle and release of bacterial toxins into the bloodstream.
This type of infection is caused by certain types of clostridial bacteria that are present in the environment. Some of these bacteria live in the horse’s intestines and don’t cause problems under normal conditions. They are present in manure and form spores that last a long time in the environment.

Sometimes clostridial spores may be deposited or inoculated into a horse’s muscle. This can happen when an injection is given in the muscle with a needle (intramuscular injection), or if the horse has a wound that affects the muscle.
A clostridial infection can happen with any kind of injection, but flunixin meglumine has been the most common.

Symptoms

Treatment

To treat the infection, large incisions are made into the muscle and fascia to expose the bacteria to oxygen and debride dead tissue. General supportive care is critical because these bacteria produce toxins that have secondary effects on the horse, including the potential to reduce the contractility of the heart. Horses are commonly treated with high doses of intravenous penicillin, intravenous fluids, cardiovascular support, and wound care. Hyperbaric therapy, where available, is suggested as an adjunct to routine treatment.

Prevention

There is no definitive prevention for clostridial myositis. Intramuscular injections should be given in large and well vascularized muscle groups. A sterile needle, a new syringe should be used and a clean spot on the horse chosen. If you notice swelling later or if the horse is not doing as well you’d expect, get veterinary help – the sooner the better.