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 wormers share a common purpose in ensuring your horse remains healthy 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.

When choosing wormers it help to know exactly which parasites each horse wormer targets.

Fenbendazole-Based Wormers
Effective Against:

  • Redworms
  • Pinworms
  • Roundworms
  • Stomach hair worms
  • Large-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:

  • Large roundworms
  • Large strongyles
  • Pinworms
  • Threadworms
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:

  • Redworms
  • Pinworms
  • Roundworms
  • Lungworms
  • Stomach hair worms
  • Large-mouthed stomach worms
  • Neck and intestinal threadworms
  • Tapeworms
  • Bots
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.


Praziquantel
Effective Against:

  • Roundworms
  • Tapeworms
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:


  • Redworms
  • Pinworms
  • Roundworms
  • Intestinal Threadworms
  • Tapeworms
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:

  • Encysted small strongyle larvae
  • Bot 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.


Sample Paste Wormer Rotation Schedule
6 times per year, every other month recommended worming
January/February
  • Anthelcide EQ Paste or oxibendazole
  • Panacur Paste or fenbendazole
  • Safe-Guard Paste fenbendazole

March/April
  • Agri-Mectin Paste or 1.87% ivermectin
  • ComboCare or 2% moxidectin & 12.5% praziquantel
  • Equell Paste or 1.87% ivermectin
  • EquiMax Paste or 1.87% ivermectin & 14.03% praziquantel
  • Equimectrin Paste or 1.87% ivermectin
  • Horse Health Ivermectin Paste or 1.87% ivermectin
  • IverCare Paste or 1.87% ivermectin
  • Quest Gel or moxidectin
  • Rotectin 1.87% Paste or 1.87% ivermectin
  • Zimecterin Paste or 1.87% ivermectin
  • Zimecterin Gold Paste or 1.55% ivermectin & 7.75% praziquantel

May/June
  • Equi-Cide Paste or pyrantel pamoate
  • Rotectin P Paste or pyrantel pamoate
  • Strongid Paste or pyrantel pamoate
  • Strongylecare Paste or pyrantel pamoate
  • TapeCare Plus Paste or pyrantel pamoate

July/August
  • Anthelcide EQ Paste or oxibendazole
  • Panacur Paste or fenbendazole
  • Safe-Guard Paste or fenbendazole

September/October
  • Agri-Mectin Paste or 1.87% ivermectin
  • ComboCare or 2% moxidectin & 12.5% praziquantel
  • Equell Paste or 1.87% ivermectin
  • EquiMax Paste or 1.87% ivermectin & 14.03% praziquantel or
  • Equimectrin Paste or 1.87% ivermectin
  • Horse Health Ivermectin Paste or 1.87% ivermectin
  • IverCare Paste or 1.87% ivermectin
  • Quest Gel or moxidectin
  • Rotectin 1.87% Paste or 1.87% ivermectin
  • Zimecterin Paste or 1.87% ivermectin
  • Zimecterin Gold Paste 1.55% ivermectin & 7.75% praziquantel

November/December
  • Equi-Cide Paste or pyrantel pamoate
  • Rotectin P Paste or pyrantel pamoate
  • Strongid Paste or pyrantel pamoate
  • Strongylecare Paste or pyrantel pamoate
  • TapeCare Plus Paste pyrantel pamoate

To keep your horse in tip-top shape, it is important to rotate dewormers to prevent dewormer resistance from developing.

This schedule is a very basic dewormer rotation program. If you suspect your horses may have tapeworms or would like a deworming program customized to your region or conditions, consult your veterinarian for a course of treatment.

If you feed a daily dewormer, such as Strongid C or Strongid C 2X, be aware that it is not effective against bots, so you should deworm once in the fall and once in the spring using a 1.87% equine ivermectin paste dewormer to control bot infestations.

• Be sure to clean up any spilled dewormers, since it can be toxic to other animals.