What are Horse Wormers?

Horse wormers (or dewormers) eliminate internal parasites in your horse. They are administered orally in paste, pellet or liquid form. All horse wormers are simple to use, easy to obtain and relatively inexpensive.

Until 2005, horse wormers were recommended on regular intervals of 4 to 8 weeks; but since that time experts have come to believe that healthy adult horses do better with quarterly or biannual dewormings.

Horses that are exposed to more frequent wormings will build up a resistance, while horses left to minimal exposure will build up a strong immunity to internal parasites over time. If you are in doubt as to when to use a horse wormer, fecal egg count tests are available through your veterinarian. It should be noted that the tests are only 40% to 90% accurate for tapeworms and bots.

Horses are treated for a variety of internal parasites such as tapeworms, large and small strongyles, pinworms, bots, hairworms, lungworms, threadworms, and mouth and stomach worms. With the exception of Ivermectin, Moxidectin, and Prazuantel, resistance to horse wormers has become extensive.

Ivermectin is possibly the most important contribution to horse wormers. It can be used for all classes of parasites with the exception of tapeworms, which primarily threaten pastured horses. For those with tapeworm concerns, a combination Ivermectin/Praziquantel or Ivermectin/Pyrantel is available and can be administered spring and fall. For all other parasites, a simple regimen of Ivermectin every season change will suffice.

Ivermectin will not remove roundworms in horses under the age of two years. Those youngsters should be given a combination of Ivermectin and Praziquantel to meet their needs. It should also be noted that Moxidectin should not be used in foals less than 6 months of age.

Of the natural horse wormers, diatomaceous earth (DE) is often suggested. Though it is great for insect elimination around the barn and in the stalls, and is often used successfully in cows and sometimes in horses, it can cause internal bleeding in horses. This internal bleeding can lead to impactions or weaken the walls of the stomach lining. DE can also throw off the pH balance and create an intestinal environment that will cause a common upset to become a dangerous one. Therefore, many horse owners feel that it should not be taken internally and can cause your horse to colic. Other natural horse wormers such as garlic, cloves, pumpkin seeds, tobacco and toxic metals have been proven ineffective and in some cases there is a narrow margin of safety exposing your horse to them.

Daily wormers are low dose Pyrantel Tartrate. The goal is to kill recently ingested larvae of worms before they get a chance to mature or do damage. Most horses develop a strong resistance to all horse wormers but especially those given on a daily basis. It is recommended that these daily wormers not be relied on, as they simply do not offer enough protection. This is especially true for high-risk horses; mainly old, immune compromised or horses less than one year of age.

If you have suspicions that your horse has intestinal parasites, the symptoms are:

It is advised to use equine probiotics several days after a horse worming. This will replenish the natural organisms in the digestive tract that have been killed off by the horse wormer.

Worming your horse is simple and should not be traumatic for him. If your horse is suspicious or resistant to accepting the horse wormer, it is best to begin by introducing a carrot into your horse’s mouth. By placing the carrot between his teeth and moving it around, this will accustom him to accepting things being put in his mouth. Once he is comfortable with the carrot, you can replace it with the horse wormer.

Many horse wormers are available in apple or molasses flavoring. This will contribute to your horse's eagerness to accept his worming.