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Equine Protozoal Myeloencephalitis (EPM)

Know the Signs of EPM, a Master of Disguise In addition to an altered gait, horses with EPM can have paralysis of muscles of the eyes, face, or mouth, evident by drooping eyes, ears, or lips.   EPM Horse

Photo: Noah D. Cohen, VMD, PPH, PhD, Dipl. ACVIM

Equine protozoal myeloencephalitis (EPM) is a debilitating neurologic disease that cannot be ignored. More than half of all horses in the United States—and in some areas as many as 90%—have been exposed to the disease’s causative agents. Its ability to masquerade as other health issues, such as lameness or other neurologic diseases, can make it difficult to diagnose. While Sarah Reuss, VMD, Dip. ACVIM, of Merial Veterinary Services, says some horses exposed to EPM’s causative agents will not develop the clinical disease, horses under stress are more likely to show signs. In some cases, horses can even be infected without showing signs for months or years or ever. When horses do show signs, it can go misdiagnosed because it can slowly progress and infect any portion of the central neurologic system, mimicking other conditions. Left untreated, EPM can lead to permanent damage. Reuss emphasizes the importance of early detection by horse owners and farm managers, veterinary diagnosis, and an effective treatment plan. “These are the keys to stopping the progression of the disease,” she says. “The faster treatment begins, the better the chance for the horse to recover.”   How Does a Horse Get EPM in the First Place? It starts with a protozoal parasite, most commonly Sarcocystis neurona, via the opossum after it ingests contaminated tissue from intermediate hosts such as the armadillo, skunk, or raccoon. In its infective stage, the sporocysts are passed through the opossum’s feces, which the horse comes into contact with as he grazes or eats or drinks contaminated feed or water. Once consumed, the sporocysts travel from the intestine into the bloodstream and cross the blood/brain barrier where they can cause inflammation and damage the horse’s central nervous system. Researchers now know that a second organism—Neospora hughesi—can also cause EPM, however this protozoan parasite’s life cycle is less well-understood. Early Diagnosis is Crucial “EPM can evolve slowly or present suddenly with varied signs from mild to severe,” Reuss says. There are several factors that can determine its progression and severity, including:
  • How long the horse has been infected;
  • The points in the brain or spinal cord where the sporocysts have infected; and
  • Stressful events during EPM infection.
“Lesions, inflammation, and pressure may develop in the brain, brain stem, or spinal cord,” Reuss says. “Depending on the location, they can affect how the disease presents itself and can make it tricky to diagnose.” She notes that the American Association of Equine Practitioners has listed these EPM clinical signs to watch for:
  • Incoordination, weakness, and/or abnormal gait;
  • Muscle loss on one side, usually along the topline or the hindquarters;
  • Paralysis of muscles of the eyes, face, or mouth, evident by drooping eyes, ears, or lips;
  • Loss of sensation of the face;
  • Difficulty swallowing; and
  • Head tilt with poor balance—the horse might assume a splay-footed stand or lean against stall walls for support.
She also notes that loss of coordination of the mouth, tongue, and throat area could make picking up, chewing, and swallowing feed difficult. When it’s EPM, Be Ready Veterinarians have several EPM treatment options available. The first U.S. Food and Drug Administration-approved EPM treatment is Marquis, an oral paste. EPM treatments are designed to cross the tough blood-brain barrier, reach the central nervous system and successfully kill the parasite responsible. If treated quickly and properly, horses can recover from EPM. The earlier treatment begins, the better the expected outcome.     Take-Home Message Reuss emphasizes the importance of understanding the risk and knowing the signs: “With an early EPM diagnosis and immediate, effective treatment, horses can show significant improvement, and they may return to normal activity.”    

Equine Digital Pulses

Equine Digital Pulses Hoof Anatomy and Leg Structure Checking equine digital pulses is an important horse management tool.  It can help you identify pain or inflammation in horse hooves or determine if there are possibly larger issues affecting the horse. When taking pulses, you are feeling the blood flowing through the artery going into the hooves.  If there is inflammation in the hoof, then the blood flow is restricted and backs up in the artery. The more inflammation there is in the hoof; the stronger the pulse.   Normal Pulses In a healthy horse, equine digital pulses are relatively hard to find (because there is very little blood restriction). If you are just learning, you may assume you are not taking them properly. As long as you are in the correct area of the leg, then a hard to find, faint pulse is a good sign.   Faint digital pulses are normal and usually indicate there are no major issues in the hoof. There is some natural variation in pulse strength.  All horses are different, so checking pulses frequently will help you learn your horse’s normal. Red Flags An easily felt equine digital pulse is commonly called a bounding digital pulse.  The sensation is like a throbbing headache or an injured finger.  It is not an increase in speed, but instead an increase in strength. A bounding equine digital pulse is a red flag.   It is telling you that your horse may have a health issue.  Slightly stronger is not as alarming as very strong. If the pulse seems stronger than normal, make sure to check a few times before assuming something is wrong.   Stronger pulses indicate inflammation and/or pain. Compare pulses in all four feet.  This way, abnormalities in one hoof will be more apparent. Which foot has the strong pulse? If there is a bounding pulse in only one hoof, then suspect a localized issue, possibly an abscess or maybe a bruise.  More than likely this is a pain response to an injury.   Stronger pulses in two or four feet indicate possibly a  bigger problem. Your horse may have laminitis.  Before you panic, look at your horse carefully.  If he appears normal, happy and comfortable, then it may be a common variation in his pulses.  If, on the other hand, you are noticing foot discomfort, personality changes or anything that leads you to believe he is not doing well, then suspect laminitis. The strength of the pulse and your horse’s behavior will help you determine what you should do. Strong bounding digital pulses and hoof sensitivity are often the first signs of laminitis. If the conditions causing inflammation are addressed quickly, the horse should improve rapidly with very few complications. This is why taking pulses is such a useful management tool. Trust yourself and your horse If the horse looks miserable or you are overly alarmed, call your veterinarian. Use your common sense.  Trust your horse and your instincts. Learn to take digital pulses before there is a problem.     How It is funny how different it is to do something verses teach it.  I have taken digital pulses for years and never have really thought about how I did it. I scoured the Internet to see what was out there and found very few pictures clearly showing how to take pulses.  I put this information together in a way that would help me if I were learning without hands on help. Normal equine digital pulses can be very hard to detect.  If you know the anatomy of the lower leg, it will help immensely.  If you are touching the correct area of the leg and having a hard time finding the pulse, then more than likely, the pulse is normal. Digital Pulse1   There are two noticeable grooves in the lower leg. 1.) Between the flexor tendons and suspensory ligament. 2.) Between the cannon bone and suspensory ligament. The vein/artery/nerve run in the groove formed between the flexor tendons and the suspensory.  (The groove I have labeled as number 1.)   The veins, Arteries and Nerves (VAN) are bundled together.  When you take the digital pulse, it is blood flowing through the artery that you feel. Digital Pulse2   This is an enlargement showing the :
  1. Vein/Artery/Nerve  (VAN)
  2. The Suspensory Ligament
  3. The Deep Digital Flexor Tendon
  4. Superficial Flexor Tendon
  The VAN then jumps over the ligament that covers the sesamoids and goes down the pastern. Here is a photo showing the ligament.  It is the collateral sesamoidean ligament. Digital Pulse3 Digital Pulse4 Don’t confuse the VAN (1) with the extensors branches of the suspensory ligament (2). The ligament will be much harder and towards the front of the leg. I have asked many professionals to show me how they take digital pulses and have found that everyone has a favorite region on the leg. After polling many professionals, 4 areas were the most popular for finding the pulses.  Digital Pulse5   Digital Pulse6 Digital Pulse7 Digital Pulse9   If you are comfortable with finding pulses, then using your fingertips is the most sensitive way to check pulses.  Usually, I am just checking whether the pulses are strong and bounding, so I lay my fingers over the whole area.  It can be faster an accurate enough on a wiggly horse.  
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