Time to start planning to test or treat your horses for encysted small redworm

As the weather draws colder (on and off) its time to start thinking about your plan of action for encysted small redworm.

The quick version:

Either worm your equines for encysted redworm during mid-late winter using Equest, Equest pramox or panacur 5 day guard (resistance test 10-14 days if using panacur), or speak to your vet about the encysted redworm blood test as an alternative option (for horses that routinely test clear on FEC).

The longer in-depth version


Grab a cuppa, cos this is quite the lengthy subject!

This unique (and annoying) lifestage of the small redworm involves them encysting in a dormant state inside the horses gut during the winter months. As they dont breed and lay eggs they then cant be detected in normal worm counts, so we cant be certain there are non that have entered this state. Not all small redworm do encyst, and many now remain active throughout winter in an adult state (thanks global warming!) but some may, and we cant really predict if they will or wont. If a lot of redworm do encyst, once the weather warms up in spring they all start to emerge, causing possible colic as they all emerge at once and other problems associated with a heavy redworm burden. This can cause dismay to the horse owner as the horse often tested clear in the autumn on a regular worm count, but during the winter these encysted stages lay inside the horse undetected.


Treatment can often be a little tricky timing wise, as its very much weather dependant and treating too early could mean a second dose would be needed in late winter. In recent years theres a lot of emphasis on the timing of this treatment, and the importance of not rushing out at first frost to grab a pramox. Timing is everything, you want to eradicate anything thats there, but also protect the horse throughout the winter months.

When it comes to tackling this pesky parasite, the options are basically test or treat. A blood test was developed recently by Equisal (who make the fantastic tapeworm test that we stock). This blood test can detect encysted stages of redworm, and needs to have blood drawn by your vet and then sent off for testing to equisal. Its only suitable for equines who have a history of low or clear worm counts throughout the year. If your horse has tested medium or high during the year, then treatment would be more suitable. The optimal time for the blood test is between September-December, but you can also test in Jan-end of March if needed. The clever folks at Equisal are working on a saliva test version similar to the tapeworm test which we are so incredibly excited for as it will be more affordable and convenient, and as soon as its ready we will be stocking it and using it ourselves, we cant wait!

For many of us (our own yard included), blood testing via our vets is quite expensive, so the alternative and most common method of dealing with "the encysted problem" is to give a treatment during the winter months. We tend to aim for Christmas or New Year as its easy to remember each year and get into a habit, ensuring you dont miss this dose. This does depend on the weather, if its a very mild winter then waiting until later in January is now recommended. 

The only chemicals that kill these encysted stages are:

Moxidectin (this is Equest green tube and Equest Pramox blue tube). This is a suitable choice for most healthy horses, its still our most effective wormer, and lasts up to 12 weeks, although reports of reduced activity time are becoming more frequent and we are personally seeing reinfection after just 8 weeks here in the lab due to its over use in the equine industry causing resistance to creep in.

When using Equest products its important to weigh your horse to dose effectively. You dont want to under dose but equally this is a strong wormer, you dont want to overdose as the safety margin is lower than the older traditional wormers. We hear often "oh I just give a full tube", but unless your horse is bang on 700kg a full tube wont be needed, and research has shown we often overestimate how much our horses weigh. You can use a weigh tape (we have some for sale on the website or you can grab one at a tack shop), but they can be a little inaccurate so add on 10% to the result to avoid under dosing. Moxidectin will also cover bots which would be a good choice especially if you live in an area with bot issues (summer sores).

When you dose with moxidectin its always a good idea if possible to stable your horse for up to 72 hours after treatment. This chemical is harmful to our dungbeetles & can also harm fish if it drains into the waterways, so we want to avoid as much residue that passes in the dung ending up on the pasture as possible.

In certain cases an Equest product may not be suitable for your equine. This would include those with bad ulcer problems as the gel can irritate the gut and cause a flare up, severe lami prone equines, or those with other health issues, or young foals etc. For these the only other chemical that kills encysted stages is panacur 5 day guard (fenbendazole). This is the liquid bottle that you add to feed for 5 days. It does have resistance issues, and if you choose to use this its worth doing a worm count 10-14 days after use to check for resistance..

Each year there is a lot of confusion with clients unsure what to do because their horses have tested clear or low, and no treatment is needed right now based on the result. These horses should still be treated for encysted stages at some point during the wintertime, but you have a bigger window for timing, and can plan for the moment of dosing, to hit the winter window correctly but also leave it long enough to ensure the protection continues throughout the colder months until spring.

If you treat fairly early then be sure to count the weeks & aim for your next worm count no more than 12 weeks after dosing, although to be fully sure 8 weeks would be advisable as moxidectin sadly isnt lasting as long any more.

This is a huge topic which is also changing year by year as new research emerges, but this is a basic overview of it. As always, if you need advice for your individual horses please do send us a message to the page or email us at poopost@outlook.com so we can have a chat about the best course of action for you. Those of us with our parasite control calendars will see it has a cheat sheet on the side with info of what to do when, to help you plan your year of parasite control.

Finally we would like to wish all our customers a merry christmas and a happy new year, lets hope 2022 is a less crazy year for all of us, stay safe everyone both for you and your pets!

Team Poopost