Deworm debunk: Wormer rotation and resistance in horses


If you change your horse wormers each time you deworm to “prevent resistance”, check out this video.

Take it from someone who knows: Fronting this video is Martin Nielsen, an equine parasitologist from the University of Kentucky’s Gluck Equine Research Center.

Got something to say about this? You can comment below.

» Next: Why you shouldn’t worm all your horses, all the time

Follow the Gluck Center: @GluckEquineResearchCenter or on Twitter @UKGluckCenter.

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Visit Martin Nielsen’s Network for Good page, and his University of Kentucky page.

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2 thoughts on “Deworm debunk: Wormer rotation and resistance in horses

  • October 15, 2019 at 2:24 pm

    Science said to rotate. Your saying We horse owners dont have anything to rotate between bc of resistance. Untrue. Nonconventional dewormers, good sanitary practices and fecal samples show how well workers have actually lasted. The real issue is the information on deworming alternates with various opinions including the opinion above. The solemn truth is: take samples to be tested. No worms no problem. If you have worms there are other solutions . Please be aware this changes repeatedly annually in who believes in what works. Thank you.

    • October 16, 2019 at 1:45 pm

      I agree that testing is key. The problem with these rotation deworming regimens is that they are most often done without any sort of diagnostic testing – as if rotation is the solution for drug resistance.

      The information about deworming does not alternate. What I am conveying is science-based and is what is communicated by leading equine parasitologists across the world. You will not find anyone with expertise in this topic who disagrees with this. But a lot of statements are coming from less educated sources or from sources with a commercial bias (wanting to sell products). And that is the real challenge – this is why I decided to produce these videos.

      And it is true that in many cases there are no dewormers to rotate between as ascarids and strongyles are commonly found resistant to two out of three available drug classes.


      Martin K Nielsen


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