Worming Horses: When, Why and How to Deworm Responsibly

• Test before you treat – faecal egg counts (FEC) reveal what's actually there.  FECs are not reliable for detecting tapeworm.  A Saliva test is available.
• Use strategic, not blanket deworming – Target specific parasites when needed
• Work with your vet to minimise resistance and protect long-term horse health
• Seasonal timing matters – Different parasites peak at different times of year
• Good land management reduces parasite burden naturally

Gone are the days when responsible horse owners would routinely worm their horses every six to eight weeks, regardless of parasite load. This traditional blanket worming approach, while well-intentioned, has contributed to widespread anthelmintic resistance that threatens the health of horses everywhere.

Today's horse worming guide focuses on strategic, testing-led approaches that protect both individual horses and the broader equine community. Modern worming strategies emphasise precision over frequency, using targeted treatments based on actual parasite burdens rather than calendar dates.

This shift isn't just about being more scientific – it's about ensuring the wormers we rely on today will still be effective for future generations of horses.

Strategic worming, also known as targeted selective treatment, represents a fundamental change in how we approach parasite control. Rather than treating all horses automatically, this approach involves testing first, then treating only when necessary based on individual parasite loads.

The problems with over-worming are significant:

• Accelerated development of drug-resistant parasites
• Unnecessary chemical burden on horses' systems
• Disruption of beneficial gut microbes
• Increased costs without improved outcomes
• Environmental contamination from excess chemicals

The long-term benefits of targeted worming include preserving wormer effectiveness, reducing treatment costs, and maintaining healthier gut ecosystems in horses. Most importantly, this approach helps ensure that effective treatments remain available when horses truly need them.

Faecal Worm Egg Counts (FWECs) are the cornerstone of strategic deworming. These laboratory tests detect and count parasite eggs in horse manure, identifying the presence of roundworms, redworms (small and large strongyles), and other parasites.

A FWEC involves collecting a fresh manure sample and having it analyzed by a veterinary laboratory. Results typically show egg counts per gram, helping determine whether treatment is necessary. Generally, horses with counts below 200 eggs per gram may not require immediate treatment, while those with higher counts warrant intervention.

Saliva tests have revolutionized tapeworm detection. Unlike FWECs, which can't reliably detect tapeworms (since these parasites don't consistently shed eggs), saliva tests measure antibody levels that indicate tapeworm presence.

Recommended testing frequency:

• FWECs: 3-4 times annually, depending on individual horse risk factors
• Saliva tests: 1-2 times per year, typically in spring and autumn or four months after treatment for Tapeworm
• New arrivals: Always test before introducing to established herds

Industry guidelines from veterinary organisations and the British Equine Veterinary Association consistently emphasise testing as the foundation of responsible worming schedules.

Effective horse worming schedules align with parasite life cycles and UK seasonal risk patterns:

Autumn (September-November)

• Primary focus: Tapeworm testing and treatment
• Conduct saliva tests for tapeworm detection - peak risk period in the UK
• Treat positive results with appropriate tapeworm-specific wormers
• Consider FWEC testing before winter housing or continued turnout

Winter (December-February)

• Primary focus: Encysted small redworms
• Use moxidectin-based wormers to target encysted larvae (typically December/January)
• Critical timing for UK horses due to milder winters allowing parasite survival
• Plan treatments for late winter emergence as temperatures begin to rise

Spring (March-May)

• Primary focus: Monitoring as grazing resume
• Conduct FWEC testing as horses increase grass intake
• Treat based on individual results rather than blanket treating
• Monitor for weather-related increases in parasite pressure during UK's variable spring weather
• Saliva test for Tapeworm

Summer (June-August)

• Primary focus: Peak grazing season monitoring
• Regular FWEC testing, especially during warm, wet periods typical of UK summers
• Target treatments based on individual test results
• Increased vigilance during hot, humid spells when parasite development accelerates

Remember that regional variations within the UK and individual veterinary surgeon advice should always inform your specific seasonal approach.

Foals and youngstock require special consideration in any deworming program. Young horses lack the immune resistance that adult horses develop through controlled parasite exposure.

Foal worming protocols typically include:

• First treatments starting around 2 months of age
• Regular treatments every 8 weeks during the first year
• Specific attention to ascarid (roundworm) control
• Gradual transition to strategic deworming as immune systems mature
• Broodmares should receive strategic care that protects both mare and foal, with particular attention to timing treatments around foaling and breeding cycles.

New arrivals present unique challenges and opportunities:

• Always quarantine and test new horses before mixing with established herds
• Conduct comprehensive FWEC and saliva testing
• Treat if necessary before introducing to clean pastures
• Use the quarantine period to establish the horse's individual parasite profile

This approach protects existing horses while giving newcomers the best possible start in their new environment.

Effective parasite control extends far beyond the medicine cabinet. Smart paddock management can dramatically reduce parasite pressure and support your strategic worming efforts.

Essential pasture practices include:

• Regular muck removal – at least twice weekly, more frequently in heavily used areas
• Paddock rotation – allowing fields to rest and breaking parasite life cycles
• Appropriate stocking densities – avoiding overcrowding that increases contamination
• Strategic resting – leaving paddocks horse-free for several weeks when possible

Co-grazing with sheep or cattle can naturally disrupt parasite cycles, as most horse parasites cannot complete their development in other livestock. This biological control method complements chemical treatments effectively.

Record keeping proves invaluable for tracking individual horse responses, seasonal patterns, and the effectiveness of your management approach over time.

Even with strategic approaches, it's crucial to verify that treatments actually work. Faecal Egg Count Reduction Tests (FECRTs) measure wormer effectiveness by comparing egg counts before and after treatment.

Conduct FECRTs by:

• Performing FEC testing before treatment
• Administering the chosen wormer according to manufacturer instructions
• Retesting 10-14 days post-treatment
• Calculating the percentage reduction in egg counts
• A reduction of less than 90% may indicate resistance developing and warrants veterinary consultation about alternative treatment options.

This monitoring ensures you're using effective products and helps identify emerging resistance before it becomes a serious problem.

"The shift towards strategic worming represents one of the most important advances in equine parasite control in decades," explains Lisa Ripley, SQP Registered Animal Medicines Advisor (RAMA). "We're seeing horse owners achieve better parasite control with fewer treatments by focussing on testing and targeted interventions."

Becky Miles, also an SQP Registered Animal Medicines Advisor (RAMA), adds: "Strategic worming is a game-changer for equine health management for horse owners. By using tools like faecal egg counts, horse owners can determine whether a horse actually needs treatment, rather than relying on routine or blanket worming schedules.  This is often the most cost-effective approach as well as being more environmentally friendly.”

Both experts emphasise that successful strategic worming requires partnership between horse owners, veterinary surgeons, and qualified advisors to interpret results and recommend appropriate actions.

Even with a whole host of information available on the topic, there are a lot of common misconceptions around worming so Harry Hall ambassador Anna Robinson caught up with Kirsty Hodgson, Director and SQP at Westgate Labs, to dive into the topic and shed some light on what worm egg counts can (and can’t) tell us alongside other testing methods.

How often should I test my horse for worms?

Most horses benefit from FWEC testing 3-4 times yearly, with higher-risk horses requiring more frequent monitoring. Saliva testing for tapeworms should occur 1-2 times annually, typically in spring and autumn.

What is a faecal egg count and why use it?

A faecal egg count measures parasite eggs in manure samples, providing objective data about your horse's parasite burden. This testing allows targeted treatment decisions rather than routine dosing regardless of need.

Should I treat all horses or just those with high worm counts?

Strategic worming focuses on treating individual horses based on their specific parasite loads. Horses with low counts may not require treatment, while high-shedding horses need targeted intervention.

How can I prevent worm resistance in my paddock?

Combine strategic treatment decisions with excellent grazing hygiene, appropriate stocking levels, regular muck removal, and paddock rotation. Avoid routine treatments and always follow veterinary guidance for product selection.  If possible weigh the animal to ensure the correct dosage is administered.  Under-dosing also leads to anthelmintic resistance.

Strategic worming represents the future of responsible horse care. By emphasising testing before treating, implementing seasonal monitoring schedules, and combining chemical treatments with excellent paddock management, horse owners can achieve superior parasite control while preserving treatment options for future generations.

The key lies in working closely with veterinary surgeons and qualified advisors to develop individualised approaches based on your horses' specific needs, local conditions, and risk factors.

Ready to implement strategic worming for your horses? Explore our worming range and support for sustainable horse health and take the first step towards more effective, responsible parasite control.

*Always consult with your veterinary surgeon or a qualified animal medicines advisor before making changes to your worming programme.