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Equine Parasite Control Q & A

Dr. Jeremy Frederick of the University of Minnesota answers questions about equine parasite control in this article.
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Reducing stocking density is one way to help manage equine internal parasite spread.

Recent articles on parasites and control from the University of Minnesota have elicited several additional questions regarding this topic. Below are three of the most frequently asked questions and answers.

How Long Do Deworming Medications Last?

The best way to determine how long the deworming medication is working is to have your horse's manure tested for parasite eggs. The specific products give a rough guideline for the estimated length of time the medication is good for. For example: fenbendazole (Panacur and Safeguard), mebendazole (Telmin), oxfenbendazole (Benzelmin), and oxibendazole (Anthelcide EQ) are usually effective for four weeks. Eqvalan, Phoenectrin and Zimectrin are usually effective for four to six weeks. Quest is usually effective for 12 weeks. Strongid is usually effective for four weeks. Piperazine products are usually effective for four weeks. Products such as Strongid and Anthelban are usually effective for four weeks and products such as Strongid C are usually given as daily dewormers. Deworming your horse every few months will not be enough in most cases.

Is There Anything I Can Do Besides Give Dewormers?

Dewormers are still necessary. However, management is a very essential aspect of a parasite control program and one that is often overlooked. Managing new arrivals, the existing herd, the pastures and paddocks are all important components. Here are some tips:

  1. Isolate and treat new animals on the premises to ensure that highly infected animals do not have a chance to shed parasites into the environment and infect other horses. Alternatively, require that new animals be dewormed prior to joining the stable.
  2. Monitor young horses closely as they are particularly susceptible to parasitic diseases.
  3. Watch the stocking density. If your horses primary forage comes from gazing, ensure the animals are not overcrowded or the pasture overgrazed. A good recommendation is each 1,000 pound horse needs two acres of pasture. Rotational grazing will help reduce parasite exposure by spreading out manure, giving the manure time to break down and help reduce over grazing.

How Can I Tell If My Parasite Control Program is Working?

Monitoring the effectiveness of a parasite preventative program is necessary. You should still test fecal egg counts at least once per year. Testing and monitoring will also help detect unusual parasitic infections. In some situations, certain parasites will not be killed using common strategies and additional medication might be necessary. 

You and your veterinarian can develop a complete and cost-effective parasite control program that is best suited for your farm and your animals. The health, happiness and productivity of your horses will make the effort more than worthwhile.

The author of this article was Jeremy D. Frederick, DVM, University of Minnesota.