💊 Vet Guide: Using Quest (Moxidectin) for Deworming Horses | 2025 Small Strongyle Control & Safe Dosing Tips 🐴

By Dr Duncan Houston, BVSc

When it comes to protecting horses from dangerous intestinal parasites, **not all dewormers are created equal**. One of the most effective tools against today’s most stubborn parasite—the small strongyle—is a product called **Quest**, which contains the active ingredient **moxidectin**. 🧪🐎

In this 2025 guide, I’ll explain how Quest works, when to use it, and how to avoid potential side effects by ensuring proper dosing. ⚖️💊

🦠 The Problem: Encysted Small Strongyles

Today’s biggest parasite threat in horses isn’t large strongyles—it’s **small strongyles** (cyathostomins). These parasites have a unique and dangerous trait: they **encyst (hide) in the intestinal wall**, where most dewormers can’t touch them. 🔬

Here’s How It Works:

• 🌱 Horses ingest larvae from contaminated pasture
• 🧬 Larvae burrow into the lining of the large intestine and encyst
• 🔥 When they emerge, they cause inflammation, colic, weight loss, and diarrhea

**Encysted larvae are not killed** by most standard dewormers, including ivermectin. This is where Quest shines. ✨

✅ Why Use Quest (Moxidectin)?

Quest is part of the **macrocyclic lactone** class of dewormers, like ivermectin—but with one major advantage: it’s effective against **encysted stages of small strongyles**. 💥

Benefits of Quest:

• ✅ Kills encysted larvae that other dewormers miss
• ✅ Longer duration of effect than ivermectin (up to 12 weeks)
• ✅ Convenient single-dose paste formulation

The only other product shown to kill encysted larvae is **Panacur PowerPac** (fenbendazole), but it requires a **five-day, double-dose regimen**, and it’s less effective against other parasite stages. 📉

⚠️ Side Effects: Why Caution Is Required

While Quest is effective, it’s also **potent**, and accidental overdosing can lead to serious reactions—including neurological signs or even death. ❗

Most Side Effects Occur When:

• ⚖️ The horse’s weight is underestimated
• 📦 The entire syringe is given to a smaller horse or pony
• 🐴 The product is given to foals, minis, or debilitated horses

Prevent Problems By:

• 📏 Using a **weight tape** or scale for accurate dosing
• 🐎 Avoiding use in underweight, old, or frail horses without vet guidance
• 🧠 Following your vet’s deworming plan based on fecal egg counts

📋 When to Use Quest in a Deworming Program

Quest is best used **once or twice a year**, as part of a strategic parasite control plan. It’s especially valuable in **late fall or early spring**, when encysted larvae are preparing to emerge. 🌱📆

Suggested Timing:

• 🌿 Late autumn—removes encysted larvae before winter stress
• 🌸 Early spring—minimizes larval emergence and pasture contamination

Always pair Quest with **pasture management** and **fecal egg counts** to ensure you’re not over-treating or contributing to drug resistance. 🔄🧪

📲 Use Ask A Vet to Plan Safely

The Ask A Vet app makes deworming smarter and safer:

• 📋 Log your deworming history and FEC results
• 📱 Get dosage guidance for Quest and other products
• 🧪 Ask about timing based on your region and climate
• ⚠️ Learn how to avoid overdosing and monitor for side effects

Protect your horse while minimizing resistance and risk. 🐴📲

✅ Quest Takeaways for 2025

• 🦠 Quest (moxidectin) is one of the **few products that kills encysted small strongyles**
• 📈 It’s more effective than ivermectin for long-term control
• ⚠️ Accurate dosing is critical to avoid toxicity—especially in small or young horses
• 📆 Use seasonally as part of a targeted deworming plan
• 📱 Use Ask A Vet to track and plan your deworming routine safely

📲 Final Thoughts from Dr Duncan Houston

Parasite control isn’t about using more—it’s about using the right tool, at the right time. Quest gives us a powerful weapon against small strongyles, but like any powerful drug, it requires caution. Talk to your vet, dose accurately, and monitor your herd for best results. 🧠💙

Download the Ask A Vet app to build your strategic deworming program, track Quest doses, and get expert help on parasite control in 2025 and beyond. 🐎📱