🩺 Contagious Equine Metritis (CEM): A Vet’s 2025 Guide | Dr Duncan Houston BVSc

Meta description: CEM is a reportable, sexually transmitted bacterial disease causing infertility. Learn to detect, treat, prevent & use Ask A Vet for breeding safety.

1. 🧪 What Is Contagious Equine Metritis?

Contagious Equine Metritis (CEM) is a reportable venereal disease caused by the Gram-negative bacterium Taylorella equigenitalis. It causes inflammation of the mare’s reproductive tract and temporary infertility, and can establish chronic carriers in both mares and stallions :contentReference[oaicite:3]{index=3}.

2. ⚠️ Why It Matters

• Highly contagious via live-cover breeding or contaminated semen and equipment :contentReference[oaicite:4]{index=4}.
• Can cause temporary infertility or early abortion in mares :contentReference[oaicite:5]{index=5}.
• Asymptomatic carriers—stallions and mares—can silently spread the disease :contentReference[oaicite:6]{index=6}.
• Detection of CEM can disrupt export/import of breeding stock :contentReference[oaicite:7]{index=7}.

3. 🕵️ Clinical Signs

Mares: Symptoms appear 10–14 days after exposure with mucopurulent vaginal discharge, shortened estrous cycles, and reduced fertility :contentReference[oaicite:8]{index=8}. Some may abort early in pregnancy :contentReference[oaicite:9]{index=9}. After recovery, mares may become long-term carriers :contentReference[oaicite:10]{index=10}.

Stallions: Typically asymptomatic carriers—no signs but shed bacteria from urethral fossa, sheath, and prepuce :contentReference[oaicite:11]{index=11}.

4. 🔬 Diagnosis

• Genital swab culture on selective media is gold standard :contentReference[oaicite:12]{index=12}.
• PCR testing is increasingly used for rapid detection :contentReference[oaicite:13]{index=13}.
• Complement fixation serology aids in mares—but ineffective in stallions :contentReference[oaicite:14]{index=14}.
• Test breeding protocols may be required for stallions after antibiotic treatment :contentReference[oaicite:15]{index=15}.

5. 🛠️ Treatment

Both mares and stallions undergo a five-day regimen:

• Topical genital washes (e.g., 4% chlorhexidine) :contentReference[oaicite:16]{index=16}.
• Application of antibiotic ointment (nitrofurazone, gentamicin) daily :contentReference[oaicite:17]{index=17}.
• Repeat swabs weekly until at least two consecutive negative results over several weeks :contentReference[oaicite:18]{index=18}.

Prognosis is generally good—mares regain fertility and carriers can be cleared with treatment :contentReference[oaicite:19]{index=19}.

6. 🛡️ Biosecurity & Prevention

• Quarantine & test all breeding-age imports from CEM-affected regions :contentReference[oaicite:20]{index=20}.
• Hygiene practices: Disinfect breeding equipment, gloves, and wash between breedings :contentReference[oaicite:21]{index=21}.
• Monitor breeding stock: Test healthy stallions and mares annually or before service.
• Avoid carrier mating: Remove or treat carriers before breeding plans begin.
• Regulatory vigilance: Compliance with USDA/APHIS and OIE notification protocols :contentReference[oaicite:22]{index=22}.

7. 🌍 Global Perspective & Trade Impact

CEM is largely eradicated in North America, but common in Europe, Africa, Asia, and South America. Quarantine and testing programs have controlled outbreaks :contentReference[oaicite:23]{index=23}. A 2008–2010 U.S. outbreak tied to imported stallions underscored trade risks :contentReference[oaicite:24]{index=24}.

8. 🧠 Ask A Vet Support

• 📋 Customized quarantine and testing timelines for imports.
• 📸 Remote review of breeding hygiene and stall setups.
• 📆 Automated reminders for retesting, breeding clearances, and follow-ups.
• 🎓 Expert webinars on venereal disease prevention, mare fertility planning, and breeding biosecurity protocols.

9. ❓ FAQs

Can a stallion test negative but still spread CEM?

Yes—because of carrier status; combined culture, PCR, and test breeding ensure safety :contentReference[oaicite:25]{index=25}.

Will treated mares regain fertility?

Most do—infertility is temporary; follow-up treatments ensure carrier status is resolved :contentReference[oaicite:26]{index=26}.

Any vaccine available?

No—no vaccine exists yet. Control depends on detection, treatment, and biosecurity :contentReference[oaicite:27]{index=27}.

Is there risk to humans?

No—T. equigenitalis is host-specific to equines; zoonotic risk is negligible :contentReference[oaicite:28]{index=28}.

10. ✅ Final Takeaway

CEM is a serious, economically impactful disease—but with vigilant testing, treatment, and biosecurity, it can be controlled. Early detection, import scrutiny, and breeder education are key. As Dr Duncan Houston, I recommend leveraging Ask A Vet to build safe, sustainable breeding programs and safeguard your equine genetics into 2025 and beyond.