Ask the Vet: EPM

Question: My Thoroughbred gelding is 24-years-old and has Cushing’s Disease and now we suspect EPM. He is being treated for both. What are the odds of a full recovery from EPM – I mean will I ever be able to ride him again? .

Answer: According to current research information, around 70% of horses treated for EPM with appropriate medications and protocols will respond and return to their previous performance levels. Your horse is suffering from two separate diseases, however; so his return will depend on how readily each affected system (hormonal, or endocrine, and neurologic) is able to respond to treatments. There may be some overlap in symptoms from each disease. Hopefully the medications and management strategies will allow your guy to reach his full potential again. Your gelding is lucky to have you!

Question: My 11-year-old Appendix gelding was diagnosed/treated for EPM when he was 5 years old. He only showed very mild symptoms (easily pulled off balance with tail pull, stands “quirky” with legs crossed). I’ve ridden him moderately over the years, even doing some low hunter courses with him, but lately he seems to be getting weak. He slips and slides in our indoor arena, apparently not getting his hind feet firmly planted while cantering around. My question – can EPM return after a long “remission” and what can I do to strengthen my geldings’ back and hindlegs so he doesn’t slip so easily? Should we treat him again with medication?

Answer: Unfortunately, EPM is a disease process that can relapse after an apparently successful treatment regimine. The protozoal agent, Sarcocystis neurona, can lie dormant for many years before causing a horse to have any signs of neurologic instability. Weakness, balance deficits, lameness, and lack of coordination can all be symptoms of EPM. The same signs are found as well in a multitude of disease processes, including equine motor neuron disease, equine polysaccharide storage myopathy, and west nile virus syndrome.

That said, I would strongly suggest having your veterinarian perform a full physical examination of your gelding to determine if an EPM relapse is happening. It is possible your vet will want to treat with another, longer-term course of medications. Traditionally sulfa drugs coupled with pyrimethamine were used to “paralyze” the protozoa. Newer drugs have come into use including ponazuril (Marquis) and nitazoxanide, or NTZ, (Navigator). Ponazuril is a form of a coccidiostat, a drug class that inhibits the replication of coccidia protozoa but may not effectively kill every organism in the central nervous system.

Nitazoxanide was originally developed for human AIDS patients and has also been found to kill the sarcocystis protozoa.  In the meantime, use caution working your gelding in order to prevent him from stumbling or falling and causing injury to himself or a rider/handler. Once he has been examined and a diagnosis made, exercises for restrengthening his topline and his hind limbs can include lots of walking, stretching his head, neck, and back long and low to activate his lumbar and gluteal muscles and lift his belly. Ensure that your arena footing is firm, not too deep, and not slippery. Walking up hills is an excellent strengthening routine once he is deemed safe to work.