Keeping your horse healthy means staying on top of deworming and parasite control, but it may not be as simple as just giving the same dewormer every few months. Parasites are becoming more resistant to medications, and a horse’s exposure depends on where they live and how they’re managed. At Aspen Veterinary Clinic, we understand that each horse is unique, and their deworming protocol should be customized accordingly. In this blog, we will outline best practices for deworming, effective parasite control strategies, and the importance of Fecal Egg Count (FEC) testing in defending your horse's health. Here's everything you need to know directly from the insights of a trusted veterinarian.
Best Practices for Deworming Horses
When it comes to deworming, there’s no one-size-fits-all solution. Every horse is unique, and their deworming protocol should reflect that. Factors like geographic location, living conditions, and exposure risks play a role. For example, the parasites common in Flagstaff, Arizona, are different from those in Lexington, Kentucky, and horses on pasture face different risks than performance horses in stalls.
So, what’s the best practice? Start with a Fecal Egg Count (FEC) test once or twice a year. This test identifies which parasites are present in your horse’s manure and determines how heavy their parasite load is (low, medium, or high), helping veterinarians create a targeted treatment plan. This tactic avoids the common mistake of blindly rotating dewormers, which can lead to drug resistance.
Some of the most common parasites affecting horses include:
- Small Strongyles (Cyathostomins)
- Large Strongyles
- Roundworms (Parascaris species)
- Tapeworms (Anoplocephala perfoliata)
- Pinworms (Oxyuris equi)
- Bots (Gasterophilus species)
- Stomach Worms (Habronema and Draschia species)
Most of these are identified through fecal egg counts, though some may require specialized procedures like gastroscopy to detect.
Choosing the Right Dewormer for My Horse
It’s imperative to understand that not all dewormers are the same and every horse is different. Younger horses, like colts and fillies, tend to be more prone to parasites since they can be a bit more inquisitive and often explore their surroundings, including manure. On the other hand, older horses may have higher parasite loads simply due to years of exposure.
Weight is another important factor. Dewormers need to be dosed accurately based on your horse’s weight to guarantee effectiveness and avoid the risk of drug-resistant parasites. If you’re unsure of your horse’s weight, your veterinarian can help determine it during their next wellness visit.
Always use FDA-approved equine-specific medications labeled for your horse’s age and weight. Also, make sure the product has been stored properly—avoid leaving it in extreme conditions like direct sunlight or freezing temperatures to ensure it stays effective.
Signs Your Horse May Have a Heavy Parasite Load
Knowing what to look for when it comes to parasites is essential for keeping your horse healthy. While some horses may not show obvious symptoms, certain signs can be a red flag that it’s time for an exam. Parasites can cause serious health issues if left untreated, so catching them early can make a big difference.
- Weight loss
- Dull or poor coat condition
- Diarrhea
- Colic symptoms
- Coughing or nasal discharge
- Itching or tail rubbing
If your horse is showing any of these symptoms or hasn’t had an exam in the past year, schedule with us as soon as possible.
Parasite Control and Prevention Strategies
One of the best ways to keep parasites under control is by managing manure properly. Believe it or not, about 10% of horses in a herd carry 90% of the parasites, and once a horse is a high or low shedder, they usually stay that way for life. That’s why regular manure testing is so important—it helps us pinpoint which horses actually need deworming, preventing unnecessary medication use and keeping parasite levels in check.
Pasture Management Tips
Keeping parasites under control starts with smart management. Here are some key steps to reduce the risk of infestations:
- Clean up manure regularly from stalls, paddocks, and pastures to limit parasite exposure.
- Test new horses for parasites before introducing them to the herd to prevent the spread.
- Only deworm when necessary based on fecal test results—no more guessing!
- Rotate pastures and prevent overgrazing to break up parasite life cycles.
- Group horses by age and risk level—for example, keeping older horses separate from young ones can help reduce transmission.
Since parasites thrive in different conditions depending on moisture and temperature, the best management practices will vary based on where you live. Talk to your veterinarian about the most effective strategies for your specific area.
Dewormer and Parasite Resistance
Over time, parasites have developed resistance to dewormers because they have been overused and improper deworming practices. Unfortunately, once resistance develops, there are no alternative medications, meaning some dewormers may no longer work at all. That’s why a targeted deworming approach based on FEC testing is the best way to effective parasite control.
How to Prevent Dewormer Resistance
- Follow your vet’s recommendations for deworming, remember every horse’s needs are different.
- Use only FDA-approved, equine-specific dewormers and always dose based on weight.
- Avoid unnecessary or rotational deworming and treat only when needed.
- Store dewormers properly to maintain effectiveness.
Collaborating with Your Veterinarian
Effective parasite control isn’t just about sticking to a routine, it’s also about having the right strategy. The old method of deworming every few months without testing is outdated and can actually make parasites more resistant to treatment. Instead, the best way to protect your horse’s health is by working with your veterinarian to create a customized parasite control plan that includes Fecal Egg Count (FEC) testing and smart pasture management.
If your horse needs a parasite control plan or FEC testing, Aspen Veterinary Clinic in Flagstaff, Arizona is here to help! Call 928-526-2423 to schedule an appointment.