🧬 Vet Insight: Genetic Testing for Equine Diseases | 2025 Breeding, Health & Risk Management Guide 🐴

By Dr Duncan Houston, BVSc

Genetic testing has revolutionized modern horse breeding and disease prevention. Once limited to pedigree confirmation, DNA tests now help identify horses at risk for inherited diseases—before symptoms arise or breeding choices are made. 🧠🔬

In this 2025 guide, we’ll explore the most common equine genetic diseases with available testing, why some breeds appear more affected, and how to use these tools to build a healthier herd. 🐴🧪

🔍 Why Genetic Testing Matters

Inherited conditions can silently pass from generation to generation. Without genetic testing, breeders risk propagating diseases that can lead to chronic pain, poor performance, or even premature euthanasia. 🧬📉

Genetic testing helps:

• 🧪 Identify disease carriers or affected individuals
• 📋 Make informed breeding decisions
• 🚫 Prevent production of foals with debilitating disorders
• 🧠 Support early diagnosis and proactive care

🧫 Key Equine Diseases with Available Genetic Tests

🦠 1. **Squamous Cell Carcinoma (SCC)**

This **cancer** affects areas exposed to UV light—especially the eyes, lips, and prepuce. It’s common in **Belgians and Haflingers**, where a genetic predisposition is linked to pigment and UV sensitivity. ☀️🧬

Test Available: Yes. Breeders can test for SCC risk before mating.

💪 2. **Immune-Mediated Myositis (IMM)**

IMM causes rapid muscle loss in **young Quarter Horses**, often after a viral infection or certain vaccinations. It’s an autoimmune reaction against muscle tissue. 🚨

Test Available: Yes. Helps identify at-risk foals and plan vaccinations more cautiously.

⚡ 3. **Polysaccharide Storage Myopathy (PSSM Type 1)**

PSSM is a form of **tying up** caused by abnormal sugar storage in muscle cells. It causes stiffness, reluctance to move, sweating, and pain. It affects over **30 breeds**, including **Quarter Horses, Belgians, and Percherons**. 🏋️

Test Available: Yes (for PSSM1)

📉 Note: **PSSM Type 2** also causes tying up, but no genetic test exists yet. Diagnosis requires a muscle biopsy.

🌬️ 4. **Equine Asthma (Heaves)**

This chronic respiratory disease was previously called **heaves**. It may have genetic components, but is also heavily influenced by environment (dust, allergens). 🫁

Test Available: Not yet. Likely involves multiple genes, making testing more complex.

🐴 Why Quarter Horses Appear More Affected

It may seem like **Quarter Horses** have more genetic diseases than other breeds—but that’s misleading. The **American Quarter Horse Association (AQHA)** has simply led the charge in genetic research and testing. 🎯📊

This proactive stance benefits the breed by improving transparency and encouraging smarter breeding—something other registries are starting to follow. 🧠🏇

📋 How to Use Genetic Testing Wisely

Genetic testing isn’t just for breeders. It’s also helpful for owners buying a horse or planning a training program. 🛒🧪

✅ Smart Uses for Genetic Testing:

• 🧬 **Pre-breeding screening** – Avoid high-risk pairings or affected foals
• 📜 **Purchase decisions** – Know what you’re buying
• 💉 **Preventive care** – Modify vaccination or training plans based on risk
• 📚 **Registry requirements** – Many breed associations now mandate or recommend testing

🧾 Cost & Testing Process

Genetic testing is usually done via a simple **mane or tail hair sample** or blood draw. Results typically return within 1–3 weeks. Costs vary by test and lab but often range from $50–$150 per condition. 💰📈

Major labs include:

• 🧪 UC Davis Veterinary Genetics Laboratory
• 🧬 Etalon Diagnostics
• 📦 Animal Genetics, Inc.

Always consult with your vet before ordering tests independently—they can help interpret results and explain next steps. 🧠💼

📲 Ask A Vet for Genetic Guidance

The Ask A Vet app helps horse owners make sense of genetic results and plan next steps. Use it to:

• 📄 Upload test results for veterinary review
• 📱 Ask about breeding risk and disease expression
• 📦 Choose the right tests for your horse or prospective purchase
• 📊 Get personalized care strategies for affected horses

It’s your digital genetic advisor—backed by real equine professionals. 🐴📲

✅ Equine Genetic Testing Takeaways

• 🧬 DNA testing can identify risks for diseases like SCC, IMM, and PSSM1
• 🐴 Quarter Horses appear overrepresented due to strong research initiatives
• 📋 Use tests to guide breeding, training, and purchase decisions
• 💰 Tests are affordable, easy to perform, and give long-term insights
• 📱 Ask A Vet helps interpret and apply test results effectively

📲 Final Thoughts from Dr Duncan Houston

Genetic testing is one of the smartest moves a horse owner or breeder can make. It protects your horse, your breeding program, and the future of your chosen breed. Whether you’re buying, breeding, or simply curious about your horse’s health, testing offers clarity and control. 🧠🐴

Download the Ask A Vet app today to get expert guidance on equine genetics, personalized health plans, and better decisions—before the next foal is even born. 🐎📱