🦠 Vet’s 2025 Guide to Clostridial Myositis in Horses

By Dr Duncan Houston BVSc

1. What is Clostridial Myositis?

Clostridial myositis, also known as gas gangrene, malignant edema, or clostridial myonecrosis, is a rapidly progressive and potentially fatal bacterial infection of skeletal muscle caused by Clostridium bacteria—gram-positive, anaerobic, spore-forming organisms. :contentReference[oaicite:3]{index=3}

2. How It Occurs

• Intramuscular injections, especially of flunixin meglumine (“Banamine”), are the most common cause—creating an anaerobic environment where Clostridia thrive. :contentReference[oaicite:4]{index=4}
• Deep wounds and blunt trauma may also provide entry for spores. :contentReference[oaicite:5]{index=5}
• Clostridial spores may exist dormant in muscle and germinate under tissue damage or compromised blood flow. :contentReference[oaicite:6]{index=6}

3. Onset and Clinical Signs

• Signs typically appear within **6–72 hours** of injection or trauma. :contentReference[oaicite:7]{index=7}
• Local swelling, heat, severe pain, subcutaneous crepitus from gas pockets. :contentReference[oaicite:8]{index=8}
• Rapid progression to fever, depression, tachycardia, anorexia, toxemia, and possible recumbency. :contentReference[oaicite:9]{index=9}
• Mortality can be high—between 30–70%—if not treated promptly. :contentReference[oaicite:10]{index=10}

4. Diagnosis

• Based on history and rapidly worsening local symptoms. :contentReference[oaicite:11]{index=11}
• Aspiration yields malodorous, serosanguinous fluid—with gas in tissues detectable by ultrasound or palpation. :contentReference[oaicite:12]{index=12}
• Gram stain/culture shows gram-positive, spore-forming rods. Tissue biopsy, PCR, or fluorescent antibody testing can identify species. :contentReference[oaicite:13]{index=13}

5. Emergency Treatment

• Surgical intervention: aggressive fasciotomy, incisions to relieve pressure, and surgical debridement to disrupt anaerobic conditions. :contentReference[oaicite:14]{index=14}
• Antibiotics: high-dose IV penicillin (44,000 IU/kg q6–8h) ± metronidazole. Continue IV for at least 3–5 days then switch to oral for ~7 days post-resolution. :contentReference[oaicite:15]{index=15}
• Supportive care: IV fluids, NSAIDs, analgesia, and veterinary monitoring. :contentReference[oaicite:16]{index=16}
• Wound care: ongoing debridement, hydrotherapy, dressing changes, repeat incisions if needed. Survivors may have large skin defects requiring long-term management. :contentReference[oaicite:17]{index=17}

6. Complications & Prognosis

• Systemic toxemia may cause laminitis, disseminated intravascular coagulation, organ failure. :contentReference[oaicite:18]{index=18}
• Prognosis depends on early intervention; survival improves by ~40% if fasciotomy occurs within 24 hours. :contentReference[oaicite:19]{index=19}
• Species matters: C. perfringens has better survival (~20% fatal), while C. septicum or mixed infections carry worse outcomes. :contentReference[oaicite:20]{index=20}

7. Prevention Strategies

• Avoid IM injections unless absolutely necessary—prefer IV or oral administration, especially for flunixin. :contentReference[oaicite:21]{index=21}
• Use sterile technique and clean injection sites thoroughly. :contentReference[oaicite:22]{index=22}
• Monitor and immediately report injection site swelling or pain. :contentReference[oaicite:23]{index=23}
• No commercial clostridial vaccines are approved in horses; awareness and safe practices are key. :contentReference[oaicite:24]{index=24}

8. Ask A Vet Integration 🩺

Telehealth support ensures rapid response:

• Send photos/video of injection swelling or crepitus for urgent review.
• Receive guided first-aid—including incision site preparation and pressure relief advice—prior to vet arrival.
• Coordinate emergency treatment protocols, antibiotic dosing, and referral urgent care.
• Support wound care with follow-up telehealth check-ins, helping track healing and detect complications.

Download the Ask A Vet app now for fast, expert horse health support when every hour matters against clostridial myositis in 2025 and beyond! ❤️

9. Summary Table

10. Final Thoughts

Clostridial myositis is a rare but devastating condition that requires swift recognition and aggressive treatment. The key is prevention—avoid IM injections, maintain hygiene, and act fast at the first sign of swelling. Combining traditional veterinary care with Ask A Vet's telehealth support ensures timely intervention and improved outcomes, safeguarding your horse in 2025 and beyond. 🐎🩹