Winning the Worm War: A Modern Guide to Equine Parasite Prevention
Worm resistance is rising and so are the costs of mismanaging equine parasites. Learn science-backed strategies for safer, more effective deworming and how good management keeps horses thriving season after season.
Why Parasite Control Has Changed
Today’s horse owners face a new challenge: parasite resistance to traditional dewormers. What worked 20 years ago doesn't work now—rotating wormers every few months leads to “super worms,” higher vet bills, and poor gut health. Modern parasite control is grounded in science, not routine.
Understanding Common Equine Parasites
- Small Strongyles (Cyathostomes): Now the most significant threat. Insensitive to many dewormers; can cause weight loss, diarrhea, and colic.
- Large Strongyles (Bloodworms): Once more harmful but now rare with regular control.
- Ascarids (Roundworms): Mainly affect foals and young horses.
- Tapeworms: Cause colic, weight loss, and digestive blockages.
- Pinworms: More annoying than dangerous, causing itching around the tail.
What Actually Works: Targeted Deworming (Strategic Deworming)
Fecal Egg Counts (FECs)
Twice yearly (spring & fall), veterinarians recommend fecal egg count tests to determine each horse’s parasite load. FECs show who needs deworming and who doesn’t, protecting worms’ natural enemies in the environment and slowing resistance.
Only Deworm When Needed
- Treat only horses with high FECs—not the whole herd.
- Select products most effective for the parasites present, as advised by your vet.
- Rotate drug classes only when FECs indicate a reduction in product efficacy.
When to Deworm Without a Test
- All foals (3x in their first year)
- After a known outbreak or when introducing a new horse with unknown history
Smart Management Practices
- Pick manure from fields at least twice weekly.
- Rotate and rest pastures.
- Avoid overstocking and provide clean, dry turnout areas.
- Separate groups by age when possible (young horses and adults shed different parasites).
- Quarantine and test new arrivals before turnout with the herd.
Deworming Mistakes to Avoid
- Over-deworming: Wastes effort, money, and fuel’s drug resistance.
- Blindly rotating dewormers: Outdated and often counterproductive.
- Ignoring young, sick, or senior horses: Custom plans are needed for each “at risk” horse.
Signs Your Deworming Program Isn’t Working
- Persistent diarrhea or weight loss
- Dull coat
- High FECs after recent deworming
- Horses colicking repeatedly
Work with an equine vet to review and update your strategy yearly.
Member Tips: Success Stories
Canter Club members’ best results come from:
- Regular FECs—not mass deworming
- Using manure forks, composting, and careful pasture management
- Tracking each horse’s FEC and deworming treatments on a calendar
Final Thoughts
Winning the worm war is all about information, not habit. With targeted deworming, pasture management, and support from a qualified vet, horses stay healthier, resistance drops, and families save money—all while protecting the wider equine community.