Does your horse's cough need to be worried?

Webcast | What to do when your horse has a fever

Infographic | Diagnostic Imaging: Know your options

Video | How to give your horse a blanket

Horse experts answer your questions in monthly live audio events.

Join us and interview leading horse researchers from the University of Kentucky

Sale and adoption of horses

Problem solving series: How to control nuisance birds on horses

Horse 2022 Calendar: Horse Anatomy in Motion

Clostridial myositis is a rare but serious bacterial infection that causes muscle inflammation and death, and releases bacterial toxins into the blood.

Published in Horse Disease Quarterly | August 13, 2019 | Diseases and conditions, horse care, muscle and joint problems, poisoning and toxicity

Clinical symptoms will appear 6-72 hours after the injection, and the horse will initially show acute swelling, fever, and pain in the affected area. The disease progresses rapidly, and the condition of the horse may decline within a few hours. Affected animals show signs of systemic toxemia; in severe cases, death can occur quickly. Clostridium produces gas, causing the characteristic emphysema (blistering) sensation or crepitus in the area. Clostridial myositis is a real medical emergency, and survival is related to timely intervention through active antibiotic treatment and wound debridement.

Clostridium is composed of more than 150 known Gram-positive, anaerobic, spore producing bacteria. The sporulation ability of these bacteria allows long-term survival in the environment. When spores encounter hypoxic areas (such as damaged muscles), they are triggered to proliferate and produce exotoxins, which can cause extensive tissue and blood vessel damage. The Clostridium species that commonly cause myositis include Clostridium perfringens, Clostridium septicum, and Clostridium serratia.

According to reports, clostridial myositis occurs after intramuscular vaccination, ivermectin, antihistamines, phenylbutazone, vitamins, prostaglandins and the most common flunixin meglumine. In rare cases, cases may occur due to insufficient perivascular administration of the compound, pony trauma or stab wound. In a 2003 study by Peek et al., the proportion of stallions and quarter horses was too high, and the authors hypothesized that this might be due to the muscularity of these groups.

The mechanism by which bacterial spores reach horse muscles is unclear. Spores may be introduced during injection. Another theory is that bacteria migrate from the normal environment in the intestine during inflammation or colic and reach the muscles through the bloodstream. It has not been determined whether there is a link between cleaning the injection site before injection and the development of myositis. According to reports, when using non-steroidal drugs and vitamins and other irritating substances, the incidence of myositis is higher, which may be due to increased tissue damage and the creation of an oxygen-free environment.

Diagnosis includes aspiration of a small amount of liquid for anaerobic culture and Gram stain to look for the presence of Gram-positive bacilli. To treat infections, large incisions are made in the muscles and fascia to expose bacteria to oxygen and debride dead tissues. General supportive care is essential because these bacteria produce toxins that can have secondary effects on horses, including the potential to reduce heart contractility. Clostridial toxins may also cause anemia, thrombocytopenia, and leukopenia. Horses usually receive high-dose intravenous penicillin, intravenous fluids, cardiovascular support, and wound care. If feasible, hypertension therapy is recommended as an adjunct to conventional treatment.

It has been reported that compared with C. septicum or C. chauvoei, the survival rate of Clostridium perfringens infection ranges from 31% to 73%, which seems to be better. Horses that survive the initial toxemic stage of the disease have a better prognosis. Wounds caused by a combination of infection and treatment are usually large and may take weeks to months to fully heal. Horses that cannot survive show signs of intravascular clotting and multiple organ failure.

There is no clear preventive measure for clostridial myositis. In intramuscular injection, use large and well-vascularized muscle groups. If there are alternative ways, such as oral or intravenous administration, avoid giving irritating substances into the muscles as much as possible.

Contact: Rebecca Ruby, BVSc (dist), MSc, Dipl. ACVP—rebecca.ruby@uky.edu—859/257-8283—University of Kentucky Veterinary Diagnostic Laboratory, Lexington

This is an excerpt from the Equine Disease Quarterly funded by the underwriter of Lloyd's of London. 

Want more articles like this? Sign up for the Bluegrass Equine Digest e-newsletter.

More information about the Gluck Horse Research Center and the British Agricultural Horse Program.

Designed by Elegant Theme | Powered by WordPress

You need to be logged in to fill out this form