This guide covers what you need to know about worming your horse in summer - from when to test, to what to worm horses with if treatment is needed, all while helping prevent resistance and protect pasture health.

Key Takeaways:

  • Test before treating – Use faecal egg counts in summer to decide if worming is necessary.

  • Only worm if needed – Treat horses with high worm burdens; avoid routine worming.

  • Use the right product – Choose ivermectin, pyrantel, or fenbendazole in summer; save moxidectin for winter.

  • Manage pasture well – Regular poo picking, co-grazing, and field rotation reduce parasite risk naturally.

Need testing kits or worming products? Check out our horse worming range.

Summer is a key time to stay ahead of parasites, but it’s no longer about blanket worming. Thanks to growing awareness of worm resistance and the CANTER guidelines, testing before treating is now the gold standard for responsible summer horse worming.

Why Summer Horse Worming Starts with Testing

Gone are the days of worming your horse every few months on a rigid calendar. With no new wormers in development and rising resistance to the ones we do have, it’s more important than ever to take a test-led approach - especially in summer.

Worm Egg Counts (WECs)

During the summer grazing season, most horses do not need worming. Instead, a faecal worm egg count (FEC or WEC) should be used to determine if your horse requires treatment.

  • Horses with WECs above 200–250 eggs per gram (epg) are typically treated.

  • For low-risk horses, the CANTER guidelines suggest raising this threshold to 500 epg to help preserve wormer efficacy.

  • Ask your vet or SQP for advice on interpreting test results based on your horse’s risk level.

Using the Right Wormer (If Required)

If a high WEC result indicates treatment is needed, the right wormer must be chosen based on your horse’s circumstances.

The number of different wormers available for horses can be confusing. These can be divided into three groups: benzimidazoles, such as fenbendazole, tetrahydropyrimidines such as pyrantel and the macrocyclic lactones which include moxidectin and ivermectin.

Here are the main wormer options for summer:

Active ingredient Example brands Targets
Fenbendazole Panacur Equine Redworm (limited resistance)
Ivermectin Eqvalan, Eraquell, Animec Redworm, Pinworm
Pyrantel Strongid P Roundworm, Tapeworm (double dose)

Deliver the right dose

Where worming is deemed necessary, it is vital to ensure horses receive the correct amount of wormer for their weight. Visual estimation of a horse’s weight could lead to inaccuracies and most often under-dosing.

When a weighbridge is not available, a weight-tape can be used. Ask your vet or SQP about how to correctly use a weight tape, or watch the ‘how to’ video on the Virbac 3D Worming website at www.3dworming.co.uk

You can also use our horse weight calculator to help.

horse grazing

Deliver the full dose

In each syringe of wormer there is approximately one or two teaspoons of paste containing the total dose of the active ingredient. Any ‘spit-out’ can represent a significant volume of the overall dose being lost and horses receiving incorrect doses.

Under-dosing has several consequences:

  • The product will not work as it should

  • It can contribute to the rapid development of resistant worms

There are alternatives to deliver the correct wormer dose, use an ergonomic easy to handle robust syringe or, if your horse is difficult to worm with a syringe, wormer is available in a tablet form that can be simply added to the feed to take the stress out of worming.

Summer Management Tips to Reduce the Need for Worming

Good pasture and herd management are crucial in reducing reliance on wormers. Here’s what you can do this summer:

1. Don’t overstock pasture,

2. Do “poo pick” at least twice per week, again this reduces the source of infection

3. Do co-graze horses with sheep or cattle, these will act as biological vacuum cleaners as they ingest equine nematode larvae. Equine worms will not develop into adults in sheep and cattle so this will drastically reduce pasture contamination.

4. Do rotate pasture and rest fields year by year

5. Do keep young horses grazing separately from older horses. Young horses are likely to have the highest parasite burdens and be responsible for the majority of pasture contamination.

During the spring and autumn months, worming for tapeworm is also recommended. Tapeworm infestation will not be picked up by routine faecal egg counts. There are alternative tests available, such as a blood or saliva tests, however, the tests cannot differentiate current infection from previous exposure (over recent weeks to months). Praziquantel or a double dose of pyrantel are the only available drugs that treat equine tapeworm. Some modern wormers conveniently combine praziquantel with other worming drugs such as ivermectin, providing a combined wormer that treats all major types of horse worms.

Ready to Worm Smarter This Summer?

Explore our full range of horse worming products and test kits. Whether you need to test, treat, or improve your worming strategy, we’ve got you covered.

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[Brought to you by Virbac, the manufacturers of Equimax® and Eraquell®.]

Written by: VioVet