Lame or EPM?

About a year and a half ago, my horse was diagnosed with EPM, which he was treated for. Now he’s having hock issues.

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Q: About a year and a half ago, my horse was diagnosed with EPM (equine protozoal myeloencephalitis), which he was treated for, and I haven’t seen any signs since. Now he’s having hock issues. My veterinarian injected him with pure acid (he didn’t use steroids in fear of an EPM relapse). There was excess discolored fluid in all of the joints, and one was very bloody. Because they were so bad, my veterinarian came back six weeks later and injected them again. I’m desperate for a healthy, rideable horse. —via email

A: Because there is no definitive pre-mortem diagnosis for EPM, you might find significantly differing opinions from veterinarians. For gait problems, the ability to distinguish between neurological problems due to EPM and lameness can be very difficult. The likelihood of identifying the problem accurately is subjective and at least in part dependent on the experience of the examiner’s experience with neurological problems and lameness issues. I recommend you seek more than one qualified opinion. A consensus might be more likely to be accurate. In my part of the world, I believe that EPM is overdiagnosed, primarily because of the number of normal horses that test positive in both the blood and the spinal fluid.

Having said that, it is still possible that your horse has neurological impairment from other problems, such as neck arthritis instability. If you are still interested in pursuing this, I would recommend you have a specialist examine your horse and determine 1) if your horse is neurologic or if it is lame, 2) where the neurologic problem or the lameness is specifically coming from, and only then 3) what might be causing it.

If you do wind up treating for EPM again, I would recommend considering some of the newer medications available (e.g., Marquis or Navigator) if you have not already used them

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Written by:

Brad Bentz, VMD, Dipl. ACVIM, ABVP, ACVECC, owns Bluegrass Equine Performance and Internal Medicine in Lexington, Ky., where he specializes in advanced internal medicine and critical care focused on helping equine patients recuperate at home. He’s authored numerous books, articles, and papers about horse health and currently serves as commission veterinarian for the Kentucky State Racing Commission.

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