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Worming Info for all Horse Owners

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A very dear friend of mine administered a routine wormer to her horse, using a standard equine wormer that she bought from a local saddlery, and 2 days later her horse was dead from the effects of parasitic colitis.

It was a tragedy that nobody could have foretold, and I was devastated to hear of this heartbreaking loss of her beloved equine friend.

So much so that it sat severely with me for many years to come, and as time went on, I would come into contact with other horse owners, situated all over the world, who had also wormed their horses and led to a fatal spasmodic colic episode where their horse had also died.


My gut instinct kept telling me that something was wrong surrounding these occurrences. I could not get my mind to quieten over this terrible series of situations involving wormers and colic; as with every case I heard, my alarm bells grew louder and louder.

horse worms and colic

This fuelled my further research, and I investigated in more detail what could be going wrong for wormers causing these fatal colic events for our equine friends .....

In my bid for answers, I went to the experts in the field. I read articles and research papers and spoke to many Parasitologists to try to glean as much information as possible about why this could be happening.

And what I found out goes against everything we have all come to believe is true about horse wormers.....

So here goes with the ugly truth about the hows, why’s, and when’s relating to horse wormers.

Firstly, how we test for worms needs to change because faecal egg counts do not pick up the most dangerous types of horse worms, which are the real killers ....and are called ENCYSTED STRONGYLES.

I want to repeat that faecal egg counts DO NOT DETECT ENCYSTED STRONGYLE WORM LARVAE.

Yet it is these nasty little bleeders that are the reason horses die when traditional wormers are used, as they go on to cause parasitic colitis.


Because although there are many different types of worms to address in horses, these Cyathostomes in their immature form can add up to millions of larvae that bury (encyst) deep into the lining of the intestines and stomach in our horses and can sit there for sometimes years, waiting for the right time to come forth.

And guess what happens when you use a standard wormer- that due to removing the other horse worms created by using a normal wormer, a huge vacancy occurs inside the horse's body that triggers these horrible little demons to come forth en masse.

When this happens, a mass of endotoxins is released, and it’s due to this mass invasion that effectively poisons your horse, causing severe spasmodic colic to occur, which can go on to kill the horse directly or through forced euthanasia due to the extreme pain and discomfort.

What is shocking is that the folks who study horse worms are already well aware of this. Time and time again, the Professionals in this field confirmed that only 1 type of chemical wormer could address these encysted strongyles, and that was MOXIDECTIN.

Understandably, the more I learned about this, the more upset I became. As to think the world has lost so many horses to this awful situation, and yet these worm companies continue to mislead the horse-loving public with names that suggest their wormers will kill all worms, such as "broad-spectrum wormers" when they most definitely do not, is a very hard pill to swallow. 

As I still see in nearly every tack and grain score, this false claim on too many worming products to list here.

But then this is sadly what I’ve discovered in so many other areas of the horse, after all of my year's research, is that it is rarely about the horse in the billion-dollar equine industry but more so about the mighty dollar. Companies will tell you anything you want to hear to sell you their carefully marketed products purely to make money. 

Monitoring such false claims largely goes unpoliced when it’s about animals.

So, moving forward, what can you do to protect your horse from worms and the effects of a standard wormer ....

best horse wormers to help with colic
common causes of colic

Thankfully it is easy to get it right by the use of a moxidectin-based wormer to address as well as prevent worms, as it’s these combination wormers that include Moxidectin that has BEEN PROVEN to kill ALL types of worms, including these offending encysted strongyles.

Another alternative to using is what Vets call a “Panacur Bomb”- but this is hard on the horse's system, as it eradicates the all-important stomach biome. However, it has saved horses- and this is by administering a vet-recommended dose of Panacur worming paste for five days running.


While I would use this method to save a horse in an emergency, after being aware of the horse's all important digestive biome, I feel that it’s too harsh on the digestive system to use regularly as a routine worming program.

As much as I hate chemical wormers, unfortunately, there is no other type other than those that contain moxidectin that can address this situation or the dreaded “Panacur Bomb”.


Therefore we can highly recommend (in New Zealand) the wormers shown in the photos called Equest Plus or Ultra-Mox to be used twice a year as a routine way to protect against worms, or more if worms are suspected.

Plus, we strongly recommend NOT to use other types of wormers that don’t contain Moxidectin, as despite what the name suggests or the packets may claim, they could cause more harm than good.

Due to this, the old ways of wormer rotation have also not been found to help address all types of worms, so rotation is also not recommended.

Also, for anyone out there who is using natural wormers - firstly, as much as it pains me to say this, as I usually support wholeheartedly a natural approach, sadly, homoeopathic and herbal remedies do not work to address these worms in our research. And our tests have seen little to no effect in using them as a defence against any worms, but especially not in Encysted Strongyle/Small Strongyles/Cyathostomes.

As for Diatomaceous Earth. Whilst it has been found to offer a broad spectrum mineral base and is suitable for supplements, I’m afraid we have also found in our research that it doesn’t work on internal parasites, and any claims for it to do so are unproven. Once inside the body, the product is no longer dry; therefore, its parasite-shredding properties cease.

To be clear and transparent - I carried out this research for our knowledge and the needs of the horses at our sanctuary to ensure we were using the best worming approach to help the horses in our care. Therefore we are completely independent and have no agenda, purpose or association with any of the worming companies or products mentioned in this article.

Our sole purpose in recommending the mentioned products is to prevent more horses from suffering due to the misleading info on wormers and because of the research carried out, along with guidance from parasitologists.... and also because they have been proven to work.


Please Note: Moxidectin should not be used with underweight horses or foals under four months- please only use it as stated on the packet. If in doubt, consult your vet. If you are located somewhere else other than New Zealand, we highly recommend finding a moxidectin-based wormer which we have found is available in most countries.


Our worming program involves a manure management program and worming twice yearly using the moxidectin-based wormers in August at the start of spring and again in autumn. As well as worming all new horses upon arrival, we have been very happy with the positive results from this approach.


I sincerely hope this prevents the needless deaths of any more horses.

Dedicated to all the beloved horses taken way too soon due to man's greed.

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