🦠 Vet Guide: Modern Parasite Control in Horses | 2025 Deworming Resistance & Strongyle Management 🐴

By Dr Duncan Houston, BVSc

When was the last time you reviewed your horse’s parasite control plan? If you're still following the **"every 8 weeks" deworming schedule** from decades past, it's time for an update. Rising drug resistance and changes in parasite populations mean that **what worked in the 1970s no longer protects your horse today**. 🧠🐎

In this 2025 guide, we’ll explore how parasites have evolved, why resistance is a growing problem, and how to adjust your deworming plan to better protect your horse and your pasture. 🧬📉

📜 A Brief History of Deworming

In the 1960s and 70s, equine deworming was revolutionized by the discovery of **effective anthelmintics** (deworming drugs). Studies recommended deworming horses **every 8 weeks**, and for decades, this method worked beautifully. 📆

The main target back then was the **large strongyle**, a parasite known to cause severe colic. Thanks to aggressive and regular deworming, large strongyles have now become rare in managed horses. ✅

⚠️ But Today’s Threat Is Different

The problem in 2025 is not large strongyles—but **small strongyles (cyathostomins)**. These parasites are far more difficult to manage. Why? Because their **larval stages burrow into the intestinal wall**, causing damage and inflammation when they emerge. 🦠🔥

Key Challenges with Small Strongyles:

• 🧬 Most dewormers kill only **adult parasites**, not larvae
• 🦠 Larval stages cause **most of the damage** before becoming adults
• 📉 Resistance to current drugs is increasing rapidly

By the time you treat, the damage is often already done. That’s why **prevention—not just treatment—is key**. 🧠

🧪 Resistance: The Silent Crisis

Dr. Ray Kaplan from the University of Georgia warns that many of today’s dewormers are **no longer effective**—or they don’t work as long as they used to. 📉

Some farms still follow **40-year-old protocols**, treating every horse the same without considering actual parasite load. This blanket approach fuels **resistance**, rendering once-powerful medications virtually useless. 🧬💣

Signs Resistance May Be Present:

• 📈 Parasite eggs reappear quickly after deworming
• 🐎 You’ve used the same product multiple times per year
• 🧪 Fecal egg count reduction is minimal or short-lived

Resistance is irreversible—so slowing it down is critical. ⏱️

✅ What Works Now: Modern Deworming Strategy

1. 🧪 Fecal Egg Count (FEC) Testing

FEC testing identifies which horses are shedding the most parasite eggs—and allows **targeted treatment**. This is now the gold standard for responsible parasite control. 📊

2. 🎯 Targeted Deworming

Only horses with **high egg counts** are dewormed—often just **once or twice per year**. Low-shedding horses may not need treatment at all during some seasons. 📉

3. 🔁 Dewormer Rotation Based on Results

Instead of rotating drugs annually by habit, rotation is based on **efficacy and resistance testing**. This slows resistance development and extends drug usefulness. 🧠

4. 💩 Pasture Management

Controlling parasite exposure is just as important as killing worms. Clean pastures mean fewer eggs, fewer larvae, and healthier horses. ✅

• 🚮 Pick up manure at least weekly
• 🌾 Rotate pastures when possible
• 📦 Avoid overgrazing or overcrowding

📲 Use Ask A Vet to Update Your Deworming Plan

The Ask A Vet app helps horse owners transition to modern, effective parasite control strategies:

• 📋 Schedule and interpret fecal egg counts
• 📱 Get customized dewormer recommendations
• 📊 Monitor treatment results and egg count reduction
• 🔄 Avoid over-treatment and drug resistance

Smarter deworming starts with better information. 🐴📲

✅ Deworming Takeaways for 2025

• 📉 Old 8-week deworming schedules are outdated and harmful
• 🧬 Small strongyles are the main threat—larvae cause most damage
• ⚠️ Most dewormers are ineffective against larval stages
• 🧪 Fecal egg counts are essential for effective treatment
• 📱 Use Ask A Vet for a safe, resistance-aware parasite plan

📲 Final Thoughts from Dr Duncan Houston

Our understanding of parasites has evolved—and so should our approach to controlling them. By shifting to targeted deworming and using fecal egg counts, we can protect our horses and preserve the tools we need to fight parasites for decades to come. 🧠💙

Download the Ask A Vet app today to get help updating your deworming plan, tracking parasite risk, and making informed decisions for healthier horses. 🐎📱