🦠 Vet Update 2025: Rethinking Parasite Control in Horses—What Still Works? 🐴💊

Author: Dr Duncan Houston, BVSc

For decades, horse owners have followed a familiar deworming schedule: rotate drugs every 8 weeks, and all is well. But research now shows that this approach is outdated and ineffective against modern parasites. In this 2025 article, Dr Duncan Houston highlights the dangers of resistance, explains why small strongyles are the current threat, and what you can do to protect your horse. 🐎⚠️

📉 The Problem with Traditional Deworming

Many current parasite control programs are based on research from the 1960s–1980s. Back then:

• 🕗 Deworming every 8 weeks was standard
• 💉 New, highly effective drugs were being released
• 🧫 The main parasite was the large strongyle—a major cause of colic

However, those parasites have changed. Many are now resistant to today’s drugs. ❌

🧬 The Real Threat Today: Small Strongyles

Unlike large strongyles, small strongyles (cyathostomins):

• 🐛 Burrow into the intestinal wall as larvae
• 💥 Cause damage when they emerge from the gut lining
• 🧪 Are resistant to many dewormers, especially in larval form

Most dewormers only kill adult worms—after the damage is done. That’s why we must shift the focus to prevention. 🧠

💊 Which Dewormers Still Work?

Only a few products remain effective—mainly against adult parasites. The challenge is:

• 🧬 Larval small strongyles are harder to kill
• 📉 Efficacy of some drugs is shorter than in the past

This is why blind rotation or fixed schedules are no longer advised. 🧪

✅ 2025 Vet-Recommended Parasite Strategy

1️⃣ Use Targeted Deworming

• 🧫 Fecal egg count tests guide when and what to deworm
• 📆 Treat only horses shedding significant eggs

2️⃣ Manage Pasture Contamination

• 💩 Pick up manure regularly
• 🌿 Rotate pastures and avoid overcrowding
• ☀️ Use cross-grazing with ruminants (sheep, cattle)

3️⃣ Test for Resistance

• 🧪 Use fecal egg count reduction tests (FECRT)
• 📉 Monitor how well your chosen dewormer works

🧠 Dr Duncan Houston’s Advice

"The worm world has evolved—but our old methods haven’t. It’s time we treat parasite control like precision medicine, not tradition." 🐴🧬

📋 Signs of Parasitism to Watch For

• 📉 Weight loss or poor body condition
• 💩 Loose stool or manure staining
• 😴 Lethargy or dull coat
• 🌾 Reduced appetite or grazing time

Always confirm with diagnostic testing before assuming parasites are the cause. 🔬

🔚 Final Thoughts: Smart Deworming Saves Horses

Old deworming methods don’t fit today’s parasite threats. With rising resistance and hidden larval stages, the modern approach focuses on diagnostics, pasture management, and precision treatment. Don’t rely on the calendar—let testing guide your parasite control program. 🐎🧠

Need help with fecal testing or updating your deworming plan? Visit AskAVet.com or download the Ask A Vet app for expert help today. 📱🧫