Equine Deworming: Modern Parasite Control
Traditional deworming every 8 weeks is outdated. Modern parasite control uses strategic deworming based on fecal egg counts.
Internal parasites are a major health threat to horses. Large strongyles (bloodworms), small strongyles (cyathostomins), roundworms (ascarids), and tapeworms all cause disease. Decades of routine deworming have created widespread drug resistance, making strategic, evidence-based parasite control essential.
Key Points
- Anthelmintic resistance is widespread
- Fecal egg counts (FEC) identify high, moderate, and low shedders
- Only high shedders need frequent deworming; low shedders need minimal treatment
- Tapeworms require praziquantel or a double-dose pyrantel once yearly
- Pasture management — manure removal, rotation, and mixed grazing — reduces parasite burden
- Young horses and foals need more aggressive deworming than adults
Understanding Equine Parasites
Large strongyles (Strongylus vulgaris) migrate through blood vessels, causing colic and arterial damage. Small strongyles (cyathostomins) are the most common and concerning parasite — they encyst in the intestinal wall and emerge in spring, causing diarrhea and weight loss. Roundworms (Parascaris equorum) affect foals and young horses, causing impaction and respiratory signs. Tapeworms (Anoplocephala) cluster at the ileocecal junction and cause colic.
Fecal Egg Count-Based Deworming
Collect a fresh fecal sample and submit for a quantitative egg count. High shedders (>500 EPG) need deworming 3-4 times yearly. Moderate shedders (200-500 EPG) need 2-3 treatments. Low shedders (<200 EPG) need 1-2 treatments or may only need tapeworm treatment. Target treatment to the parasites present. Retest 2 weeks after deworming to confirm efficacy.
When to See a Vet Immediately
- Your horse is losing weight despite good nutrition
- There's diarrhea, especially in spring
- Colic episodes are increasing
- The coat is dull and body condition is poor
- FEC shows high egg counts
How RVC Can Help
This article is for educational purposes only and does not replace professional veterinary advice. If your pet is showing any symptoms, please contact Royal Veterinary Center immediately at +853 6677 6611.