Page 26 - Canada Spring 2021

EQUINE HEALTH
CLOSTRIDIAL MYOSITIS
Following Injections and Precautions for Banamine Injections
by Heather Smith Thomas
Many horsemen give injec- tions to their horses. These include vaccina-
tions, antibiotics, and sometimes other medications. Most injections are given intramuscularly, but there are a few medications that should always be given intravenously.
Intramuscular injections occasionally cause local abscesses if the needle or skin is dirty when the injection is given. Sometimes, abscesses occur even with very clean conditions. The worst kind of injection-induced infection is
called clostridial myositis, or myonecrosis.
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. They are often on the horse’s skin and can be taken into the tissues with an injection. These bacteria can be in a dormant state,
and then multiply when conditions are right, growing best in an airless environment without oxygen, such as bruised and damaged tissue with very little blood supply.
The dormant spores “come to life” when they have favorable conditions in which to multiply and start producing deadly toxins. Different clostridia cause different diseases. Examples include: tetanus, malignant edema, blackleg in cattle, enterotoxemia in young calves and foals, or life-threatening gut infection and diarrhea in young foals.
Some types of intramuscular injections seem more risky for clostridial infections, especially flunixin meglumine (Banamine and its generic equivalents), if given in the muscle rather than in the vein. One theory is that this drug sets up an ideal pH in the tissues for these bacteria to grow (basic,
as opposed to acidic). A clostridial infection can happen with any kind of injection, but Banamine has been the most common.
Dr. Ray Randall, a semi-retired veterinarian in Bridger, Montana, says to be aware of the possibility of adverse reaction any time you give an injection. “This can occur with vaccinations, injections of vitamin E and selenium, etc.
A horse will go off his feed and be depressed when affected by clostridial bacteria, which produces toxins that not only damage local tissues and affect the entire system but can also spread around the muscles.
26 SPEEDHORSE CANADA Spring 2021