Managing Internal Parasites in Horses: A Guide for Owners

Published on: December 9, 2024

By: Miles HenryFact Checked

Internal parasites are a persistent threat to your horse’s health, impacting performance, well-being, and longevity. With proactive strategies, you can minimize their impact and keep your horses thriving. This guide covers everything you need to know about internal parasites in horses, including their lifecycles, signs of infestation, targeted treatments, and proven prevention strategies.

Understanding Internal Parasite Lifecycles in Horse

Effectively managing parasites begins with understanding how they operate. Here’s a breakdown of the most common types and their effects:

• Strongyles (Bloodworms):
  Large strongyles, according to Penn State Extension, are particularly harmful because their larvae migrate through blood vessels, potentially causing life-threatening blockages and organ damage. Eggs are shed in manure, develop into larvae in the environment, and are ingested by horses during grazing.
• Ascarids (Roundworms):
  These primarily affect foals and young horses. The larvae migrate through the lungs and liver before settling in the intestines, often causing stunted growth and respiratory issues. Regular monitoring is critical for young horses.
• Tapeworms:
  Tapeworms use oribatid mites as intermediate hosts. Horses ingest the mites while grazing, and the tapeworms attach to the intestinal lining, where they can cause colic and blockages. The National Institute of Health highlights that these parasites are most active in late fall, making timely treatment crucial.
• Pinworms:
  These lay eggs around the anus, causing irritation and excessive tail rubbing. While less harmful, they can still affect your horse’s comfort and coat condition.
• Bots:
  Botflies lay eggs on the horse’s coat, which are ingested when the horse grooms itself. The larvae then migrate to the stomach, causing irritation and sometimes ulcers.

Pro Tip: Rotate pastures every 4–6 weeks and remove manure weekly. Use a compost thermometer to ensure manure piles reach at least 131°F to kill parasite eggs effectively.

Signs of Internal Parasites in Horses to Watch For

Early detection of parasites is vital. Look for these common signs:

• Weight loss despite proper feeding
• A dull coat and reduced energy
• Recurring colic episodes
• Pot-bellied appearance, especially in foals
• Tail rubbing and irritation

Last summer, I noticed one of my geldings losing weight and his coat dull. Initially, I suspected a dietary issue, but a fecal egg count (FEC) revealed a high strongyle load. The challenge was coordinating FEC testing during a busy season. After talking with my vet, I implemented a targeted deworming plan and fine-tuned my pasture rotation schedule. Within weeks, his coat regained its shine, and he returned to peak condition.

Effective Treatments for Internal Parasites in Horses

Targeted treatments ensure efficacy while reducing the risk of resistance.

Common Dewormers

• Ivermectin and Moxidectin:
  Effective against strongyles, bots, and ascarids. I once used Moxidectin on a horse with a high bot burden after confirming with an FEC. Within a month, his symptoms improved dramatically.
• Fenbendazole and Pyrantel:
  These are ideal for targeting roundworms and pinworms, especially in younger horses.
• Praziquantel:
  If your horse has tapeworms, Praziquantel is a reliable go-to solution that I’ve seen work wonders in late fall treatments.

Pro Tip: Consult your veterinarian for precise dosages based on your horse’s weight and FEC results. Administer tapeworm and bot treatments in late fall after the first frost to align with their lifecycle.

Targeted Deworming

Tailored deworming is based on FEC results, focusing treatments on high shedders while minimizing medication for low shedders. This approach slows resistance and reduces unnecessary exposure to dewormers.

• Collecting FEC Samples:
  Use gloves and a clean container to collect fresh manure, ideally within 12 hours of defecation. Store the sample in a cool place if immediate testing isn’t possible. Your vet will analyze it to determine the type and number of parasite eggs present.
• Implementation Tip:
  Initially, coordinating FEC testing with treatment schedules felt overwhelming. Setting up a shared calendar with my vet streamlined the process and ensured no steps were missed.

Pro Tip: Rotate dewormers annually to maintain effectiveness against a range of parasites. Refer to the AAEP Parasite Control Guidelines for more details.

Long-Term Parasite Control in Horses

Prevention is the cornerstone of long-term parasite control in horses. Maintaining a clean environment, monitoring parasite loads, and adopting strategic practices can significantly reduce reliance on chemical treatments. Consistent care ensures your horses stay healthy and thrive. Here are practical steps to include in your routine.

Manure Management

Removing manure weekly is an effective way to reduce parasite exposure in pastures. For those who compost, follow these best practices:

• Heat Matters: Ensure compost piles reach at least 131°F to kill parasite eggs and larvae.
• Verify Temperatures: Use a compost thermometer to monitor heat levels.
• Reuse Safely: Properly composted manure can be safely reused in pastures without reintroducing parasites.

Pro Tip: Group composting tasks into your weekly routine to stay consistent and reduce workload over time.

Pasture Rotation

Rotating pastures every 4–6 weeks reduces your horse’s exposure to parasite larvae while allowing grazing areas to recover. Here’s how to make the most of it:

• Minimize Overgrazing: Avoid forcing horses to graze closer to potentially contaminated ground.
• Maximize Sunlight Exposure: Allow empty pastures to benefit from natural sunlight, which helps kill parasite larvae.

FEC Testing

Regular fecal egg counts (every 3–6 months) are a cornerstone of targeted parasite management. Use these steps to make FEC testing part of your routine:

• Why It’s Important: Testing identifies parasite loads, tailoring deworming plans to individual horses.
• How to Collect Samples: Gather fresh manure within 12 hours, store it in a cool place, and have your veterinarian analyze it.
• Avoid Resistance: Regular testing reduces the overuse of dewormers, helping prevent resistance.

Pro Tip: Record FEC results and deworming schedules in a log or use our Free Parasite Management Checklist for easy tracking.

Botfly Egg Removal

During peak seasons, adding botfly egg removal to your grooming routine prevents infestations and keeps your horses comfortable. Here’s how:

• Use the Right Tools: A bot knife or similar tool ensures effective removal.
• Stay Consistent: Incorporate this into daily grooming to reduce the chance of eggs hatching.

Last year, I faced a particularly heavy botfly season and began daily egg removal during grooming. Initially tedious, it became second nature and significantly reduced infestations, strengthening the bond with my horses.

Feeding Practices

Feeding practices go beyond cleanliness—they’re an essential part of parasite control. Optimize your routine with these strategies:

• Elevated Feeders: Prevent parasite ingestion by using elevated feeders, particularly in high-grazing areas.
• Hay Nets: Using hay nets keeps forage off the ground, reducing contamination. Slow-feed hay nets mimic natural grazing behaviors, keeping your horses engaged longer.
• Clean Equipment Weekly: Wash feeders and water troughs regularly with warm water and dish soap. For deeper cleaning, use food-safe disinfectants to eliminate bacteria and parasite eggs.

Pro Tip: Group horses with similar parasite burdens together to minimize reinfection risks. Pair this strategy with regular FEC testing for optimal results.

Table for Long-Term Parasite Control

Practice	Frequency	Key Benefits
Manure Management	Weekly	Reduces larvae exposure; makes compost safe for reuse.
Pasture Rotation	Every 4–6 weeks	Limits grazing on contaminated areas; promotes pasture recovery.
FEC Testing	Every 3–6 months	Targets treatments effectively; prevents resistance.
Botfly Egg Removal	Daily (peak seasons)	Prevents infestations; improves horse comfort and health.
Feeding Practices	Daily/Weekly	Limits contamination via clean equipment and strategic feeding.

FAQs About Internal Parasites in Horses

Conclusion: Managing Internal Parasites in Horses

Managing internal parasites in horses is more than just a routine—it’s a vital part of ensuring their overall health and happiness. By understanding parasite lifecycles, spotting the early warning signs, and adopting targeted treatments and prevention strategies, you can keep your horses thriving.

Are you ready to simplify your horse’s care and take control of parasites? Download our Free Parasite Management Checklist, featuring detailed schedules, actionable tips, and space to track your horses’ deworming history. This tool makes it easy to stay on top of your horse’s health and keep parasites under control.