How often should you worm your horse? The best practice now is not to follow a strict, set schedule. Instead, you must use a plan based on testing your horse’s manure for worm eggs. This is called a fecal egg count testing horse. Your equine parasite control schedule should change based on these test results.
Moving Beyond the Old Way of Worming
For many years, horse owners just wormed their horses every six to eight weeks, no matter what. This old method is no longer recommended. Why? Because it leads to worms becoming resistant to the drugs we use to kill them. Think of it like germs becoming tough against medicine. If we use the same medicine too often, the worms survive and multiply. This makes treating them much harder later on.
Today, horse worming recommendations focus on being smart. We want to kill the harmful worms but leave the harmless ones alone. This helps slow down drug resistance. This smart approach is called strategic deworming plan.
Why the Change in Advice?
The main reason for the shift is drug resistance. Many common worms, especially small strongyles (cyathostomins), are now very hard to kill with standard treatments.
- Overuse: Too much worming means all the weak worms die, but the strong, resistant ones live.
- Environmental Load: Frequent worming might not be needed if your horse lives in a clean area.
- Safety: Some dewormers are not safe for all horses, especially very young or very old ones.
Grasping the New Approach: Fecal Egg Counts
The core of modern parasite control is the fecal egg count testing horse. This simple test tells you how many worm eggs your horse is passing in its manure.
What Does the Test Show?
The test measures the number of eggs per gram (EPG) of manure. This number helps your vet sort horses into risk groups.
- Low Shedders (Low EPG): These horses usually do not need frequent deworming.
- Medium Shedders (Moderate EPG): They need regular treatment.
- High Shedders (High EPG): These horses carry the most parasites and need the most attention.
Getting the Test Done
You must get a fresh manure sample from your horse. Do not let it sit out in the sun. Take it to your veterinarian or an accredited lab quickly. The lab will float the sample to count the eggs.
When to get a fecal egg count? Most experts suggest testing at least twice a year, usually in the spring and fall. This helps guide your main treatments.
Developing Your Strategic Deworming Plan
A strategic deworming plan looks at many things, not just the calendar date. It blends testing results with the time of year and the horse’s age.
Risk Assessment for Every Horse
Not all horses have the same risk of getting worms. Your equine parasite burden management must consider these factors:
- Age: Foals and older horses often need more care. Growing horses need constant protection.
- Past Results: If a horse always has a high EPG, they are a high-risk candidate.
- Environment: Horses kept in small paddocks or shared pastures often have more exposure.
- Climate: Warmer, wetter climates allow parasite larvae to develop faster on the grass.
- Travel: Horses that travel often and mix with other herds face higher risks.
Determining Your Deworming Frequency for Horses
Once you know the EPG, you can set the deworming frequency for horses.
| EPG Result | Risk Level | Suggested Deworming Frequency (Based on Testing) |
|---|---|---|
| Less than 200 EPG | Low Shedder | Treat 1-2 times per year after testing. |
| 200 to 500 EPG | Medium Shedder | Treat 2-3 times per year, guided by testing. |
| Over 500 EPG | High Shedder | Treat 3-4 times per year, using different drugs. |
Remember, even low shedders need some treatment, especially for dangerous worms like tapeworms and bot flies, which standard FEC tests often miss.
The Role of Veterinary Advice Horse Worming
You should never try to manage parasite control alone. Veterinary advice horse worming is essential. Your vet knows the local parasites and which drugs work best in your region.
The Importance of Drug Rotation
Parasites develop resistance to the deworming drugs, called anthelmintics. To slow this down, you must rotate the drugs you use. This is called horse anthelmintic rotation.
There are four main classes of dewormers used in horses:
- Macrocyclic Lactones (MLs): Ivermectin and Moxidectin. These are very potent.
- Benzimidazoles: Fenbendazole (Panacur) and Albendazole.
- Pyrantel: Often used for tapeworms (often given twice a year).
- Praziquantel: Also very effective against tapeworms, often given with an ML.
Example of a Simple Rotation Plan
A rotation plan ensures you don’t use the same drug repeatedly.
- Spring Treatment: Use a Macrocyclic Lactone (e.g., Moxidectin).
- Summer Treatment (If needed): Use a Benzimidazole (e.g., Fenbendazole).
- Fall Treatment: Use a drug targeting tapeworms (e.g., Praziquantel or Pyrantel).
- Winter Treatment (If needed): Use a different Macrocyclic Lactone (e.g., Ivermectin).
Crucial Note: Moxidectin is generally considered more effective against encysted small strongyles (a stage that hides in the gut wall) than Ivermectin. Many vets recommend Moxidectin for the fall treatment.
When to Give Wormer to Horses: Timing Matters
Knowing when to treat is as important as knowing what to use. The best time to worm a horse is when parasite larvae are most active on the pasture, which usually corresponds to the life cycle of the worm.
Seasonal Considerations
- Spring (March/April): This is when larvae start hatching as the weather warms. Treat after the grass starts growing, but always do a fecal test first to decide the dose frequency.
- Summer (June/July): Depending on your rainfall and temperature, a second treatment might be needed, especially for high shedders.
- Late Summer/Early Fall (August/September): This is critical. You need to target the migrating larvae and tapeworms before winter. A treatment with Moxidectin is often advised here to kill hidden larval stages.
- Late Fall/Winter (November/December): A final treatment is often given after the first hard frost. Frost kills off most surface larvae. This treatment targets any worms already inside the horse before they start laying new eggs in the spring. This is often called a “clean-out dose.”
When to give wormer to horses that are sick or stressed? Always consult your vet. Sometimes, a treatment is needed outside the regular schedule if the horse is moving to a new farm or has been ill.
Managing Specific Parasites
A good equine parasite control schedule must target more than just roundworms and strongyles.
Tapeworms (Anoplocephala perfoliata)
Tapeworms do not show up well on standard fecal tests. They are linked to gut pain (colic).
- Action: Treat for tapeworms twice a year—usually late spring and late fall. Use Praziquantel or Pyrantel pamoate.
Bots (Gasterophilus species)
Bots are fly larvae that attach to the stomach lining.
- Action: Treat with an Ivermectin or Moxidectin product after the first hard frost in the late fall. This kills the mature larvae that have migrated into the stomach before they can hatch in the spring.
Encysted Small Strongyles
These are the larval stages that burrow into the gut lining. They are the biggest concern for resistant parasites. They can suddenly emerge and cause severe diarrhea and gut damage.
- Action: Moxidectin is generally the best drug to target these hidden stages. A treatment with Fenbendazole given for five days straight can also be effective, but only under veterinary advice horse worming.
Pasture Management: The Non-Drug Approach
Worming medicine is only half the battle. Equine parasite burden management relies heavily on keeping your pasture clean. If you constantly put worms back onto the grass, no amount of deworming will solve the problem long-term.
Key Pasture Tips
- Manure Removal: Pick up manure daily or every other day. This stops larvae from maturing.
- Poop Piles: If you cannot pick manure daily, spread it out thinly. This exposes the eggs to the sun, which dries them out and kills them. Do not let manure pile up.
- Stocking Density: Do not keep too many horses in a small area. Fewer horses per acre means less contamination per bite of grass.
- Quarantine New Horses: Keep any new horse separate for several weeks and test their manure before introducing them to your main herd.
- Sacrificial Area: Use a dry, bare area (a “sacrifice paddock”) during wet seasons. This keeps horses off heavily contaminated grass when larvae are most active.
Rescaling Treatment for Different Horse Groups
Your deworming frequency for horses must change based on their life stage and workload.
Foals and Young Stock (Under 2 Years)
Young horses are highly vulnerable. Their immune systems are still developing.
- They should be dewormed regularly, often starting around 2-3 months of age.
- FEC testing might be unreliable in very young foals, so a more structured schedule is often followed initially, guided by your vet.
- They need treatment for tapeworms and pinworms early on.
Mares
Pregnant mares need special care, especially in the last trimester.
- Never worm a mare without checking with your vet first regarding the specific drug safety during pregnancy.
- Treating mares just before foaling helps ensure the foal gets a low initial parasite load.
Performance and Working Horses
Horses that travel, train hard, or compete often have higher stress levels. Stress can cause dormant larvae to reactivate.
- These horses may need more frequent monitoring via FEC tests or might fall into the medium-to-high risk shedding category.
Older Horses (Seniors)
Older horses often have weaker immune systems and may not process dewormer drugs as well.
- Regular testing is vital. You might need to use longer courses of treatment (like the five-day Fenbendazole) if resistance is suspected, as suggested by your veterinarian.
Performing a Post-Treatment Fecal Egg Count Reduction Test (FECRT)
A key part of your strategic deworming plan is checking if your dewormer actually worked. This is called the FECRT.
How to Do an FECRT
- Test 1 (Pre-Treatment): Perform a fecal egg count (FEC) right before you give the dewormer. Record the EPG.
- Treat: Administer the chosen dewormer, ensuring the dose is correct for the horse’s weight.
- Wait: Wait 10 to 14 days. This gives the drug time to kill the worms and pass through the system.
- Test 2 (Post-Treatment): Perform a second FEC on the same horse.
Interpreting the Results
The goal is to see a large drop in the EPG.
- Success: A reduction of 95% or more means the drug worked well against the susceptible worms.
- Failure (Resistance): If the EPG drops less than 90%, the worms in your horse are likely resistant to that drug. You must switch to a different class of anthelmintic for the next treatment. This is vital for equine parasite control schedule success.
Frequently Asked Questions (FAQ)
How do I know the correct dose for my horse’s weight?
Always weigh your horse using a weigh tape or a scale. Use the weight indicated on the dewormer tube. Giving too little dewormer is a major cause of resistance, as it only kills the weakest worms. Underdosing is dangerous.
Can I see tapeworm eggs on a regular fecal test?
Usually, no. Standard flotation tests are poor at detecting tapeworm eggs. This is why experts recommend treating for tapeworms twice a year, regardless of a negative FEC result.
Do I still need to treat my horse in winter?
Yes, but the treatment focus changes. In winter, the goal is usually a “clean-out” dose targeting worms already inside the horse before they can start laying eggs in spring. Once the frost hits, you can be more confident that surface larvae are not an immediate threat.
Is deworming a foal immediately after birth necessary?
Consult your vet. Some protocols suggest a very early treatment (around 4-8 weeks) for roundworms, especially if the mare was not properly dewormed during pregnancy. However, using strong drugs too early can sometimes disrupt the development of the foal’s natural gut flora.
What is the best time to worm a horse for bots?
The best time to worm a horse for bots is after the first few hard frosts of the late fall or early winter. This timing ensures the flies are no longer active and the larvae are mature in the stomach, ready to be killed by an appropriate dewormer like Moxidectin or Ivermectin.