Have you ever watched your horse rubbing its tail against a fence post and wondered if there’s something more going on than just an itch? Or maybe you’ve noticed your otherwise robust equine companion looking a bit dull and losing weight despite a proper feeding regimen. These could be signs that your horse is battling an invisible enemy: internal parasites.
As a horse owner, I’ve learned that deworming isn’t just a routine task to check off your stable management list – it’s a crucial component of your horse’s overall health and well-being. Let’s dive into the world of equine parasite control and discover how a seasonal approach can keep your four-legged friend in peak condition year-round.
But before we tackle the how of deworming, it’s important to understand the what and why. Horses are hosts to a variety of internal parasites that have evolved alongside them for millennia.
Common Internal Parasites in Horses
The parasite world is diverse and, frankly, fascinating (even if a bit gross). The most common culprits include:
Small Strongyles (Cyathostomes): These are the most prevalent worms in horses today. What makes them particularly tricky is their ability to encyst in the intestinal wall and remain dormant for months or even years.
Large Strongyles: Once the most dangerous parasite, veterinary medicine has made great strides in controlling these worms, which can cause serious damage to blood vessels and organs.
Ascarids (Roundworms): These primarily affect young horses and can grow up to 15 inches long! They compete for nutrients and can cause blockages in severe cases.
Tapeworms: These flat, segmented worms attach to the intestinal lining and can cause colic, especially at the ileocecal junction.
Bots: These aren’t true worms but the larval stage of the bot fly, which lays eggs on horse’s legs that are then ingested during grooming.
Pinworms: While less harmful to physical health, these pests cause intense itching around the tail, leading to rubbing and hair loss.
The effects of a parasite burden go far beyond just “having worms.” Parasites can cause:
– Weight loss and poor body condition despite adequate feeding
– Dull, rough coat and lack of bloom
– Reduced performance and stamina
– Pot-bellied appearance, especially in young horses
– Recurring colic episodes
– Diarrhea or inconsistent manure
– Impaired immune function
– In severe cases, life-threatening conditions like impaction colic
Think of parasites as uninvited guests that not only eat at your table but also trash your house on the way out. They consume nutrients meant for your horse, damage intestinal tissue, and can cause inflammation throughout the body.
Signs Your Horse Might Have a Parasite Problem
While a healthy-looking horse can still harbor parasites, there are some red flags that should prompt immediate attention:
1. Visible worms in the manure (though this is rare with modern parasites)
2. Persistent coughing (some parasites migrate through the lungs)
3. Recurrent colic episodes
4. Unexplained weight loss
5. Lethargy or decreased performance
6. Swelling under the belly or between the jaw bones
7. Excessive tail rubbing or itching around the anus
I once had a mare who started rubbing her tail incessantly in late summer. Despite regular deworming, she had developed a pinworm infestation that required targeted treatment and thorough cleaning of her environment. This experience taught me that parasites can be resilient and adaptable – much like the horses they infect!
The world of equine parasite control has changed dramatically over the past few decades, and staying informed is crucial for effective management. In the past, the standard recommendation was to rotate dewormers every 6-8 weeks year-round. This “rotational deworming” approach was designed to target different parasites with different drug classes. However, this has led to a significant problem: parasite resistance.
Just as bacteria can develop resistance to antibiotics, parasites can evolve to survive our deworming medications. This has led to a paradigm shift in how we approach parasite control.
Targeted Selective Treatment
The modern approach focuses on treating horses based on their individual parasite load and risk factors. Not all horses in a herd carry the same parasite burden – typically, about 20% of horses harbor about 80% of the parasites. Identifying these “high shedders” allows for more precise treatment while reducing unnecessary deworming of horses with minimal parasite loads.
This approach has several benefits:
– Reduces the development of drug resistance
– Decreases the environmental impact of dewormers
– Saves money by avoiding unnecessary treatments
– Preserves the effectiveness of our limited deworming medications
Think of it like precision medicine – we’re moving from a one-size-fits-all approach to a customized strategy based on each horse’s needs.
Essential Tools for an Effective Deworming Program
To implement a modern deworming program, you’ll need more than just paste wormers from your local feed store.
Fecal Egg Count Testing
This is the cornerstone of strategic deworming. A fecal egg count (FEC) quantifies the number of parasite eggs in a manure sample, helping to identify which horses are high, moderate, or low shedders.
The process is simple:
1. Collect a fresh manure sample
2. Keep it cool (not frozen) until it reaches the lab
3. Have your vet or an equine laboratory perform the count
4. Use the results to guide your deworming decisions
Regular FECs (usually 2-4 times per year) allow you to track changes in your horse’s parasite status and adjust your program accordingly.
Working with Your Veterinarian
Your vet is an invaluable partner in developing an effective deworming program. They can:
– Interpret FEC results
– Recommend appropriate products based on local resistance patterns
– Help time treatments for maximum effectiveness
– Adjust protocols for special cases (pregnant mares, foals, seniors)
– Monitor for signs of resistance in your herd
I make it a point to have an annual “parasite consultation” with my vet to review our program and make any necessary adjustments based on the changing needs of my horses and the evolving understanding of parasite control.
Seasonal Deworming Calendar
While individual needs may vary, a seasonal approach provides a practical framework for managing parasite control throughout the year.
Spring Deworming Protocol (March-May)
Spring is a critical time for parasite control as larvae that have overwintered on pastures become active.
Key targets: Small strongyles (including encysted larvae), large strongyles, and tapeworms
Recommended actions:
– Perform a fecal egg count as pastures green up
– Treat with moxidectin (Quest) for encysted small strongyles
– Add praziquantel (found in combination products like Quest Plus) for tapeworms
– Schedule pasture management: harrow only when hot, dry conditions will kill larvae
– Begin regular manure removal from high-traffic areas
Tip: Schedule spring deworming before the temperature consistently stays above 45°F (7°C), as this is when larvae become more active on pasture.
Summer Parasite Management (June-August)
Summer heat actually helps in parasite control by killing larvae on pasture, but certain parasites like bots and stomach worms thrive.
Key targets: Bots, stomach worms, and monitoring small strongyle egg shedding
Recommended actions:
– Mid-summer fecal egg count for high shedders
– Treat high shedders with appropriate dewormer based on FEC results
– Monitor for and remove bot eggs from legs and body
– Continue rigorous manure management
– Consider fly control measures to reduce bot fly activity
Tip: Use a bot knife or bot block to remove yellow bot eggs from your horse’s legs and body during summer months to break the life cycle of these parasites.
Fall Deworming Strategy (September-November)
Fall deworming is crucial for removing parasites before horses enter the winter season.
Key targets: All parasites, with special attention to bots and tapeworms
Recommended actions:
– Comprehensive FEC for all horses
– Treat with ivermectin to target bots before the first hard frost
– Add praziquantel for tapeworms if not addressed in spring
– Perform one final pasture cleaning before winter
– Evaluate body condition as horses enter winter
Tip: Time your fall deworming for about a month after the first killing frost to maximize effectiveness against bots that have been consumed throughout the summer.
Winter Deworming Considerations (December-February)
Winter offers a natural break in the parasite life cycle in colder climates, but indoor housing can concentrate parasites.
Key targets: Encysted small strongyles, pinworms in stabled horses
Recommended actions:
– Evaluate need for treatment based on previous FEC results
– Consider treatment with moxidectin for encysted larvae in high shedders
– Monitor stabled horses for signs of pinworms (tail rubbing)
– Maintain clean bedding and stalls
– Plan next year’s strategy based on the year’s FEC patterns
Tip: If your horses are primarily stabled in winter, pay special attention to pinworm control through thorough cleaning of stall walls, feed tubs, and grooming tools to prevent reinfection.
Best Practices for Administering Dewormers
Even the best product won’t work if it’s not given properly. Here are some tips for effective deworming:
Calculating the Correct Dosage is incredibly important, Underdosing is a major contributor to parasite resistance. To ensure your horse receives the full benefit:
– Use a weight tape or scale to determine actual weight
– Dose for 100-200 pounds over estimated weight if in doubt
– Adjust the dial on paste wormers precisely
– For liquid formulations, use a proper oral syringe
– Don’t split tubes between horses unless using a weight-calibrated syringe
Remember, most adult horses weigh more than the standard 1,000-pound setting on many dewormer tubes. A typical 16-hand warmblood can easily weigh 1,200-1,400 pounds!
Have a Difficult Horse?
We all know that horse who could win Olympic gold in avoiding the dewormer. Here are some tricks I’ve learned over the years:
1. Mix with a small amount of applesauce or molasses in a syringe
2. Apply a small amount of honey to the tip of the syringe
3. Administer while feeding to catch them off guard
4. Use a grooming session to relax them before attempting
5. Practice with an empty syringe and reward good behavior
For the extremely difficult horse, your vet can prescribe dewormer in a flavored form or provide alternative administration methods.
Complementary Management Practices
Deworming alone is only half the battle. Effective parasite control requires a holistic approach to management.
Pasture Management for Parasite Control
The pasture is where the parasite life cycle continues, so breaking it here is extremely effective:
– Remove manure at least twice weekly from grazing areas
– Rotate pastures when possible, allowing several weeks of rest
– Harrow only during hot, dry conditions (over 85°F/29°C for several days)
– Avoid overgrazing, maintain pastures at 3-4 inches minimum
– Consider mixed grazing with sheep or cattle, which consume horse parasite larvae
– Manage stocking density – more space means less parasite pressure
Quarantine Protocols for New Horses
New additions can bring unwanted parasites to your farm. A proper quarantine protocol includes:
1. Keep new arrivals separate for at least 3-4 weeks
2. Perform a fecal egg count upon arrival
3. Deworm with a broad-spectrum product like moxidectin plus praziquantel
4. Repeat FEC two weeks after deworming to ensure effectiveness
5. Use separate equipment, grooming tools, and manure removal tools
6. Integrate gradually after confirming low parasite status
I learned this lesson the hard way when I brought home a rescue horse who introduced a resistant strain of small strongyles to my property. An ounce of prevention is truly worth a pound of cure!
Deworming Special Cases
Certain horses require special consideration in your parasite control program.
Foals and Young Horses
Foals are particularly vulnerable to parasites, especially ascarids (roundworms):
– Begin deworming at 2-3 months of age
– Focus on ascarid control with fenbendazole or oxibendazole
– Deworm every 2-3 months until one year of age
– Perform first FEC at 6-8 months
– Avoid ivermectin and moxidectin until over 4-6 months of age
– Continue more frequent monitoring through 2 years of age
Senior Horses with Special Needs
Older horses may have compromised immune systems or special considerations:
– Monitor body condition closely
– Perform FECs more frequently (3-4 times yearly)
– Adjust dosing for weight loss if necessary
– Consider the impact of medications for conditions like Cushing’s disease
– Be vigilant for signs of parasite-related colic or diarrhea
– Maintain more aggressive environmental control
Environmental Concerns and Resistance Management
The way we deworm affects more than just our horses – it impacts our entire ecosystem and the future effectiveness of our medications.
To be good stewards of both our horses and the environment:
1. Avoid deworming before heavy rain that could wash chemicals into waterways
2. Compost manure properly before spreading on fields
3. Keep detailed records of treatments and FEC results
4. Use all classes of dewormers only when indicated by testing
5. Work with neighboring farms to coordinate parasite control strategies
6. Participate in resistance testing if available in your area
Remember, the dewormers we have now are the only ones available – there are no new classes of anthelmintics in development for horses. We must preserve their effectiveness through judicious use.
Deworming horses has evolved from a simple calendar routine to a science-based, targeted approach that benefits both our horses and the environment. By adopting a seasonal strategy that combines strategic chemical treatment with thoughtful management practices, we can keep our equine partners healthier while fighting the development of resistant parasites.
Remember, the goal isn’t to eliminate every parasite – that’s neither possible nor desirable. Instead, we aim to maintain parasite populations at a level that doesn’t impact our horses’ health while preserving the effectiveness of our deworming medications for the future.
Take the time to work with your veterinarian, learn to collect and submit fecal samples, and adjust your approach based on your specific situation. Your horses will thank you with better health, improved performance, and longer, more comfortable lives.
5 important FAQs About Horse Deworming
1: Can I just use the same deworming schedule for all horses on my property to keep things simple?
While it might seem convenient, treating all horses on the same schedule regardless of their individual parasite loads contributes significantly to resistance development. Studies show that about 20% of horses carry 80% of the parasite burden in a herd. By identifying and targeting these “high shedders” through fecal egg count testing, you can reduce unnecessary treatments while more effectively controlling parasites overall. This approach is better for your horses, your wallet, and the future effectiveness of dewormers.
2: I’ve heard that some horses develop diarrhea after deworming. Is this normal, and should I be concerned?
Mild, transient diarrhea can occur in some horses after deworming, particularly if they had a high parasite load. This typically results from the die-off of large numbers of parasites. However, severe or prolonged diarrhea is not normal and warrants veterinary attention. To minimize this risk, horses with suspected heavy parasite burdens should be introduced to a strategic deworming program gradually, sometimes starting with a less potent dewormer before moving to more broad-spectrum products. Always consult your veterinarian if diarrhea persists for more than 24-48 hours after deworming.
3: Is it true that some natural or herbal products can replace chemical dewormers?
While many natural products are marketed for parasite control, there is currently no scientific evidence that herbal dewormers can effectively replace conventional anthelmintics. Some herbs may have mild antiparasitic properties, but they haven’t been proven to adequately control the diversity and quantity of parasites that affect horses. The best approach is to use evidence-based methods like fecal egg count testing and targeted treatment with proven dewormers. That said, good management practices like proper composting, pasture rotation, and manure removal are “natural” methods that definitely reduce parasite pressure and should be implemented regardless of which deworming products you use.
4: My horse spits out most of the dewormer paste. How can I be sure they’re getting the full dose?
This is a common and frustrating problem! To ensure your horse receives the full dose: 1) Position the syringe barrel at the back corner of the mouth in the space between the teeth, 2) Elevate the horse’s head slightly while administering, 3) Immediately close the mouth and hold it shut for a few seconds, 4) Stroke the throat to encourage swallowing, and 5) Have a helper ready with a dose of molasses or applesauce to chase the dewormer. For particularly difficult horses, your vet can prescribe flavored dewormers or powder formulations that can be mixed in feed. Remember that underdosing contributes to resistance, so it’s worth taking the time to ensure proper administration.
5: How long should I wait after deworming before letting my horse back out on pasture?
This is an excellent question that addresses both parasite control and environmental concerns. For most modern dewormers, you should keep your horse confined for 24-48 hours after treatment to prevent recently killed parasites and their eggs from being deposited on clean pasture. This is particularly important when using dewormers that target encysted small strongyles or tapeworms. During this confinement period, remove manure promptly and dispose of it in a composting system rather than spreading it on fields. This practice helps break the parasite life cycle and reduces the environmental impact of deworming medications.
