Equine Worming Advice
What are worms?
Worms are internal parasites that live in the digestive system of horses. Almost all horses carry some level of worm burden — this is completely normal. Problems arise when that burden becomes too high, which can lead to:
- Weight loss
- Dull coat
- Diarrhoea
- Poor performance
- Colic
- In severe cases, life-threatening complications
The aim of modern worm control is not to eliminate worms entirely (which is neither possible nor desirable), but to keep worm burdens at a low, safe level.
Why has worming advice changed?
Over the last decade, veterinary advice has changed significantly due to increasing drug resistance.
Many common worms have developed resistance to widely used worming drugs (known as anthelmintics), including:
- Ivermectin
- Pyrantel embonate
- Benzimidazoles
- Even moxidectin
When worms become resistant, these medications become less effective — and in some cases, may no longer work at all. This is a growing and serious concern in equine health.
Historically, horses were wormed every 6–8 weeks on a rotational basis. We now know that this approach has contributed to resistance and is no longer considered best practice.
Our Recommended Worming Programme
1. Faecal Worm Egg Counts (FEC)
For adult horses, we recommend a faecal worm egg count (FEC) every 12 weeks.
- This simple test measures the number of worm eggs in your horse’s droppings.
- The results should always be discussed with a vet, who can advise whether treatment is necessary and, if so, which product is most appropriate.
- Many horses do not require treatment every time they are tested.
This targeted approach helps reduce unnecessary worming and slows the development of drug resistance.
2. Tapeworm Control
Tapeworm should be assessed at least once yearly.
This can be done in one of two ways:
- Testing via a saliva test or blood test
- Alternatively, annual treatment with a praziquantel-based product
Because tapeworm testing can be more expensive, some owners choose to administer a praziquantel treatment once a year instead of testing. We are happy to advise on the most suitable approach for your horse or yard.
3. Encysted Redworm (Small Redworm)
Encysted small redworm is a significant concern in the UK. This stage of the worm life cycle burrows into the gut wall and:
- Can cause severe disease
- May lead to colitis, weight loss, diarrhoea and colic
- Can be life-threatening in heavy burdens
Importantly, encysted redworm does not show up on faecal worm egg counts.
For this reason, we recommend that horses are treated once yearly in late autumn or early winter with a moxidectin-based product to target this stage.
There are blood tests available to assess encysted redworm risk; however, their accuracy is not fully proven. If you are considering testing rather than routine treatment, this should be discussed with one of our vets.
Young Horses and Foals
Worm control in foals and young horses is different from adult horses, as they are more susceptible to certain parasites and may require a tailored approach.
Worming programmes for youngstock should always be discussed individually with your vet.
Good Pasture Management Matters
Effective worm control also relies on good management practices:
- Poo picking at least twice weekly
- Harrowing is not recommended as it can make the problem worse
- Avoiding overstocking
- Rotational grazing where possible
- Keeping young horses away from heavily contaminated pasture
A Responsible, Targeted Approach
By testing regularly and treating only when necessary, we:
- Protect the long-term effectiveness of worming drugs
- Reduce the risk of resistance
- Provide safer, more sustainable parasite control
- Potentially reduce unnecessary costs
If you would like help setting up a testing schedule or discussing a worming plan for your horse or yard, please contact the practice — we are happy to help.
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