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Controlling internal parasites is one of the most important things you can do for your horse. All horses are continually exposed to dangerous parasites in their environment whether they are international- level competitors or backyard pets. Young horses are the most at risk for illness related to parasite infestations but all horses are susceptible. Common conditions associated with parasite infestation include colic, diarrhea, respiratory disease, anemia, weight loss and skin diseases. Horses heavily infested with parasites may show the classic pot-bellied, unthrifty appearance most horse owners recognize. Signs may also be more subtle such as poor performance, dull haircoat or repeated mild colic episodes. Even horses that appear perfectly healthy require more feed to maintain their weight if they are supporting a population of parasites. The more chronic the infestation, the more permanent damage is done to the intestinal tract and other internal organs. This can cause illness or death years after the initial infestation.

Most horse owners are already aware of the most common intestinal parasites: large and small strongyles, roundworms, pinworms and botfly larvae. Many do not realize, however, that there are dozens of species of parasites that can infect other tissues, such as the lungs, skin or liver. Even parasites that spend most of their lives in the intestinal tract commonly migrate through other organs on their way to the gut, causing damage and illness. In recent years, research has shown that even tapeworms can cause disease in horses, just as they do in dogs and cats.

Fortunately, control of these unwelcome guests is relatively simple. For most farms and stables, there are three options available to keep horses healthy and at peak performance. A discussion with the veterinarian at your next wellness visit can help you decide which option works best for you and your horses.

The first option is based on the use of Strongid C2X Daily Dewormer. Along with using the daily dewormer year-round, horses on this program are also dewormed twice annually with an Ivermectin or Moxidectin dewormer that includes praziquantal (for control of tapeworms); once in the late spring and once in the fall after a killing frost.

The second option is a Rotational Deworming program. This program is based on the use of a different chemical class of dewormer every 8 weeks. We recommend three classes of dewormer be employed in this plan: 1)Ivermectin(Equimax, Eqvalan, Zimectrin); 2)Moxidectin(Quest); 3) Benzimidazole(Panacur, Safeguard, Anthelcide). Products containing praziquantal are used twice a year to control tapeworms(Quest Plus, Equimax, Zimectrin Gold). A recommended schedule would look something like this:

January-February: Panacur
March-April: Equimax
May-June: Quest Plus
July-August: Panacur
September-October: Equimax
November-December: Quest

The third option is a Strategic Deworming program. This program uses Fecal Egg Counts to classify each horse on the farm as a low-, moderate- or high-shedder of strongyle eggs (a measure of the horse’s innate resistance to intestinal parasites) and to determine the effectiveness of each class of dewormer on your farm. Once these parameters are established, a custom deworming program is formulated for the farm. Please see our article on Strategic Deworming for more information and details about this program.

After you decide which program you are going to use, note the dates deworming is due on a calendar that you look at regularly so that you won’t miss a dose. Having a good estimate of your horse’s weight is also crucial to a proper deworming program. Under-dosing dewormer is worse than not giving it at all as it encourages resistance in the parasite population. Ask us to “weight tape” your horses during your next wellness visit to be sure you’re giving each horse the proper dose of dewormer.

Lastly, we do not recommend use of any “natural” dewormers available on the market. These products are not regulated by the FDA and thus do not have to prove safety or efficacy. Many of these products include such ingredients as tobacco, garlic or black walnut which may have potentially severe or even fatal side effects. Regardless of any limited value these products may possess they have been rendered obsolete by modern safe and effective anthelmintics.