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A Look At The Different Horse Wormers

By Jeffrey Rolo

Horse wormers come in a wide assortment of types and brand names, so much so that it's often tempting to just grab the nearest tube or box of wormer and just call it a day. After all, a wormer is a wormer brand names are just the same products offered by different companies, right? As convenient as it would be were that question true, the answer is no.

Horse worming products are different families under the same roof.

Many of us will initially compare two types of wormers to be no different than unleaded gasoline versus super unleaded gasoline; one might be of a slightly higher quality, but they serve the same purpose and the benefits of the higher priced version are arguable. In reality a better analogy would be the difference between gasoline and oil; both are very similar and are necessary to make your car run well, but they are not interchangeable as they serve two distinctly different purposes.

Continuing with the car analogy for just a little longer, horse wormers share a common purpose in ensuring your horse "runs" well by removing parasites from his body, but since each targets a separate set of parasites each should be considered a unique and necessary product. With this in mind, it should now be clear why a proper parasite prevention program rotates horse wormers regularly.

Unfortunately learning about parasites is about as enjoyable for most of us as visiting the dentist! Thankfully this article will give you the "Cliff Notes" version of parasite prevention by explaining exactly which parasites each horse wormer targets, saving you time and allowing you to move on to more enjoyable topics!

A quick sidebar before we continue: I do realize in a technical sense the term "worming" is erroneous, and that we in fact use horse de-wormers in a horse de-worming program. But most horsemen leave out the "de" when referring to wormers, so this article does the same in order to provide a quick and easy read.

Fenbendazole-Based Wormers

Effective Against:

bulletStomach hair worms
bulletLarge-mouthed stomach worms

Fenbendazole is an extremely safe wormer, able to withstand overdoses of 100-200 times the standard dose without causing harm to your horse. For this reason Fenbendazole is often used to clear immature parasites (which are particularly resistant to wormers due to their slower metabolism) from a horse by applying a dose twice a day for five days.

The most popular Fenbendazole-based wormer on the market is Safe-Guard.

Oxibendazole-Based Wormers

Effective Against:

bulletLarge roundworms
bulletLarge strongyles

Whereas Oxibendazole may not target as many parasites as others, its success rate against the above listed parasites is very impressive: 97 100% effective! In addition Oxibendazole is a safe wormer, able to withstand overdoses up to 60 times the standard dose without causing harm to your horse.

The most popular Oxibendazole-based wormer on the market is Anthelcide EQ.

Ivermectin-Based Wormers

Effective Against:

bulletStomach hair worms
bulletLarge-mouthed stomach worms
bulletNeck and intestinal threadworms

As you can see, Ivermectin is one of the most effective and well-rounded wormers available, though as with all wormers it does have its weaknesses since it is ineffective against small encysted strongyle and tapeworms. A very safe wormer, Ivermectin can be given in doses up to 60 times the standard dose without causing harm to your horse.

The most popular Ivermectin-based wormers are Zimecterin and Equimectrin.


Effective Against:


Praziquantel is not effective against many types of parasites, but it has been shown to target the abovementioned parasites very effectively when paired together with Ivermectin. As such, Praziquantel-Ivermectin blends are available in the forms of Zimecterin Gold and Equimax. These blends should be included in any rotation schedule as they are extremely effective.

Pyrantel Pamoate-based Wormers

Effective Against:

bulletIntestinal Threadworms

Note that although tapeworms are listed above, Pyrantel Pamoate will not prove terribly effective against them unless a double dose is applied. Pyrantel Pamoate wormers are safe for horses up to 20 times the standard dose.

The most popular Pyrantel Pamoate-based wormers are Strongid and Exodus.

Moxidectin-Based Wormers

Effective Against:

bulletEncysted small strongyle larvae
bulletBot fly larvae

Moxidectin has been the subject of controversy and for good reason. It is the only horse wormer that is capable of killing the above larvae in a single dose, which is a very impressive feat. Its liability is that the overdose tolerance threshold is far less than other wormers; 5 times the standard dose can cause significant damage to your horse.

Whereas it may be difficult to give an adult horse an overdose 5 times the standard dose, it's extremely easy to make this mistake when worming a foal. As such, at no time would I recommend using this wormer on foals or weakened horses.

The most popular Moxidectin-based wormer is Quest.

Knowing which parasites each of the above wormers are effective against is a good first start, but in the world of parasite prevention the difference between success and failure ultimately lies with how you plan your horse worming schedule.

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