Treating Equine Parasites with Fenbendazole by a Vet – 2025 Resistance, Roundworms & Deworming Guide 🪱🐴
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Treating Equine Parasites with Fenbendazole by a Vet – 2025 Resistance, Roundworms & Deworming Guide 🪱🐴
By Dr Duncan Houston, BVSc
Introduction
Fenbendazole, marketed as Panacur or Safeguard, has long been a staple in equine deworming protocols. But in 2025, the landscape is shifting. Due to increasing drug resistance, especially in adult horses infected with small strongyles, fenbendazole’s efficacy is now highly variable. However, for foals battling roundworms, it remains a trusted tool. This guide explores how fenbendazole performs today, and how fecal egg testing is the only way to deworm smartly.
Understanding Equine Parasites 🧬
Most Common Parasites in Horses
- Small strongyles (cyathostomes): Most problematic in adult horses
- Roundworms (Parascaris equorum): Most common in foals under 6 months
Why Resistance Matters
- Decades of frequent deworming have led to drug-resistant parasite populations
- Using ineffective products wastes money and allows parasites to thrive
- Resistance is farm-specific—what works on one property may fail on another
What Is Fenbendazole? 💊
- A benzimidazole-class anthelmintic
- Traditionally used in single-dose or 5-day double-dose regimens
- Sold under Panacur® and Safeguard®
- Sometimes used in PowerPak 5-day protocol for heavy worm burdens
2025 Research Findings 📊
A Kansas State University study evaluated fenbendazole’s current effectiveness in real-world equine settings.
Key Findings:
- Average reduction in strongyle egg count: 71.8%
- Farm-to-farm variation ranged from 40% to 100%
- Foals: More than 98% effective against roundworms
- Adults: Even at double doses for 5 days, results were unreliable
What This Means for Deworming Strategy 🧪
1. Don’t Guess—Test First
- Fecal Egg Count (FEC): Measures parasite eggs before deworming
- Fecal Egg Count Reduction Test (FECRT): Repeat test 10–14 days post-treatment
- Effective deworming = at least 90% reduction in egg count
2. Use Fenbendazole Selectively
- Still highly effective in foals with roundworms
- May not work in adult horses with strongyles—especially with one-time dosing
3. Avoid One-Time Adult Doses
- Standard fenbendazole doses are often ineffective against strongyles
- Even 5-day double doses show only partial success
Case Example: Strongyle Resistance in Adult Gelding
- 10-year-old gelding was dewormed with a 5-day PowerPak
- FEC dropped only 50%—not considered effective
- Switched to a different anthelmintic based on resistance profile
- Later FEC showed >95% drop after ivermectin + follow-up
FAQs About Fenbendazole & Parasite Control
Q: Is fenbendazole safe for foals?
A: Yes—it's one of the safest and most effective choices for roundworm infestations in young horses.
Q: Should I rotate dewormers?
A: No—not randomly. Rotation should be based on fecal testing and known resistance on your farm.
Q: Can I give fenbendazole just to be safe?
A: Avoid blind dosing. Testing is cheaper long-term and protects against resistance.
Conclusion
In 2025, fenbendazole is a powerful tool for treating foal roundworms, but its effectiveness against adult strongyles is limited and variable. Routine, untargeted deworming is no longer best practice. With parasite resistance on the rise, strategic deworming guided by fecal egg counts is the most effective—and economical—approach to equine parasite control.
Want a custom parasite control plan for your horses? Visit AskAVet.com or download our app 📱 to work with Dr Duncan Houston on fecal testing and resistance-based deworming. 🩺🐴
